Study of disorder-order transitions in FexAl1−x binary alloys using the augmented space recursion based orbital peeling technique

In this communication we propose a method for the study of disorder-order transitions in Fe_xAl_1−x binary alloys. We turn to our earlier development [1] of a combination of the recursion method introduced by Haydock et al. [2] and our augmented space approach [3] with the orbital peeling technique proposed by Burke [4] to determine the small energy differences required in obtaining the pair energies which go as input to the generalized perturbation technique [5] of studying disorder-order transitions.     

Chaos in Josephson junctions

A detailed analysis of the control space characterization of phase locked states and chaotic attractors in Josephson junctions is presented, based on a model that includes both quadratic damping and cosine interference terms. In addition, some novel features of the nonlinear characteristics of the junction like evolution of basin boundaries, bifurcation structure analysis and scaling behaviour of Lyapunov exponent are discussed.     

Synchronizing time delay systems using variable delay in coupling

We present a mechanism for synchronizing time delay systems using one way coupling with a variable delay in coupling that is reset at finite intervals. We present the analysis of the error dynamics that helps to isolate regions of stability of the synchronized state in the parameter space of interest for single and multiple delays. We supplement this by numerical simulations in a standard time delay system like Mackey Glass system. This method has the advantage that it can be adjusted to be delay or anticipatory in synchronization with a time which is independent of the system delay. We demonstrate the use of this method in communication using the bi channel scheme. We show that since the synchronizing channel carries information from transmitter only at intervals of reset time, it is not susceptible to an easy reconstruction.     

Simultaneous quantification of vasicine and vasicinone in different parts of Justicia adhatoda using high-performance thin-layer chromatography‒densitometry: comparison of different extraction techniques and solvent systems

JPC – Journal of Planar Chromatography – Modern TLC - The present study was carried out for screening an efficient extraction method and extracting solvent in different plant parts of...     

Non-linear optical properties of (Pb<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)TiO<Subscript>3</Subscript> thin films

Thin films of (Pb_1−x Sr _x )TiO₃, x=0,0.5,1.0 have been prepared on glass substrates by the chemical-solution method using the spin-coating technique. The optical nonlinearity in the visible spectral region is investigated using short (5 ns) laser pulses at the off-resonant wavelength of 532 nm employing the open aperture z-scan technique. It is found that the third order nonlinear absorption is dependent on the lead content of the films, with the compositions x=0, 0.5 exhibiting large values (β∼10⁻⁷ m/W), thereby suggesting the possible use of these materials as optical limiters. No optical nonlinearity is observed for the composition with x=1.0.     

Dynamics of the logistic map under discrete parametric perturbation

By introducing a periodic perturbation in the control parameter of the logistic map we have investigated the period locking properties of the map. The map then gets locked onto the periodicity of the perturbation for a wide range of values of the parameter and hence can lead to a control of the chaotic regime. This parametrically perturbed map exhibits many other interesting features like the presence of bubble structures, repeated reappearance of periodic cycles beyond the chaotic regime, dependence of the escape parameter on the seed value and also on the initial phase of the perturbation etc.     

Sum and difference frequency generation of white light continuum with the ps pulses of Nd:YAG laser in a thick BBO crystal

The white light continuum (WLC) generated in water/D₂O mixture by pumping with the fundamental of ps Nd⁺³:YAG laser has been used as a variable frequency source for the sum frequency generation as well as for its amplification. 35 ps long pulses with 8 mJ energy at 1064 nm were mixed collinearly with the WLC generated by the same laser beam in a 20 mm thick BBO crystal. The obtained tunable output has been identified as the sum frequency between the fundamental and a portion of the WLC with the required phase matching. Theoretical simulations are also given along with a few initial experiments to use this combination for the difference frequency generation (optical parametric amplification) under non-collinear geometry.     

Perturbative evaluation of universal constants for a quartic map

We discuss a perturbative scheme for the determination of the bifurcation rate δ for a specific map, by extending Virendra Singh’s method of evaluating the scaling factor α. The method is applied to a quartic map and the values obtained, α = 1.690781026 and δ = 7.23682924 are in good agreement with the numerically computed values reported in the literature. The perturbative approach is found to be more efficient than other existing methods.     

Chemical Composition and Antioxidant Property of Essential Oil of Callicarpa tomentosa

Chemistry of Natural Compounds -     

Synthesis and Crystal Structure of (2S,6R) Ethyl 1,2,6-triphenyl-4-(phenylamino)-1,2,5,6-tetrahydropyridine-3-carboxylate

Abstract  

The title compound, (2S,6R), Ethyl 1,2,6-triphenyl-4-(phenylamino)-1,2,5,6-tetrahydropyridine-3-carboxylate (C₃₂H₃₀N₂O₂), was synthesised by the reaction of benzaldehyde, aniline and ethylacetoacetate, in the presence of l (−) proline–Fe(III) complex, formed in situ, at room temperature. The compound was characterized by spectral methods and X-ray diffraction studies. The compound crystallizes in the triclinic space group P − 1 with the following unit-cell parameters: a = 9.651(4), b = 10.909(5), c = 13.737(7) ?, α = 106.597(7), β = 108.664(8), γ = 99.779(6)°, Z = 2. The crystal structure was solved by direct methods using single-crystal X-ray diffraction data collected at 100 K and refined by full-matrix least-squares procedures to a final R-value of 0.0633 for 3415 observed reflections. The 1,2,5,6-tetrahydropyridine ring exhibits a flat boat conformation. The structure has intra- and intermolecular hydrogen bonds of the type N–H···O, C–H···O and C–H···π, which help to stabilize the crystal structure.