Phase-shifting interferometry in the presence of nonlinear phase steps, harmonics, and noise

A phase-shifting piezo device commonly employed in phase-shifting interferometry exhibits a nonlinear response to applied voltage. Hence, a method for estimation of phase distribution in the presence of nonlinear phase steps is presented. The proposed method compensates for the harmonics present in the intensity fringe, allows the use of arbitrary phase-step values between 0 and tau rad, and does not impose constraints on the selection of particular phase-step values for minimizing nonlinearity and compensating for the harmonics. The comparison of the proposed method with other well-known benchmarking algorithms shows that our method is highly efficient and also works well in the presence of noise.     

Chirp estimation in phase-shifting interferometry

We propose a new approach for estimating the phase in the presence of a nonlinear response of a phase-shifting device: a piezoelectric transducer (PZT). The method is complemented well by the high resolution and the maximum likelihood estimation techniques in the estimation of the phase step and the nonlinear coefficient. The advantage of the proposed method is that it can be extended to the extraction of multiple phases in configurations involving multiple PZTs in the presence of nonlinearity. Symmetricity in the phase steps is not required in this method. Hence hysteresis of the PZT does not have any influence on the accuracy of the phase estimation. The effectiveness of the method is shown by experimental results.     

Influence of Catalyst on the Formation of 5(10)-Ene Ketals From Estra-4-en-3-ones

The effect of catalyst on formation of isomeric ketals from 19-nortestosterone and 19-nor-ethisterone is reported. Regioselectivity has been achieved with metal hydrides as catalyst, reported for the first time, to give 5(10)-ene ketals.

     

Geometrical parameters,vibrational wavenumbers,and relationships established with six difluorobenzonitriles

The geometry, vibrational wavenumbers, and thermodynamical parameters have been calculated using density functional methods (DFT) for benzonitrile (BN) and the six difluorobenzonitriles (DFBNs) of the series. The results were compared with the available experimental data, and correlations were established for the ? C?N and C? F moieties between the natural atomic charges and the geometrical parameters of the compounds. These relations were found as linear or slightly parabolic in most cases. Investigations were carried out to examine the effect of substituents on structural deformations and other properties. Correlations were also determined with the stretching vibrations. Other general conclusions have also been drawn. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

The stability of hydrophobic sols in the presence of surface active agents

Summary The stability of Thorium dioxide sols at p_H=3.5 was examined as a function of anionic surface active agents spectrophotometrically. At low concentrations of surface active agents, the stability of the sol decreases and attains a minimum value at concentrations 10⁻⁴ to 10⁻³ M. With increasing concentration the stability increases and attains a maximum at concentrations 10⁻³ to 10⁻² M. The effect of the P_H-value, the chain length and the head groups of the surface active agents are also studied. The results were explained on the basis of strong adsorption of these ions at the Stern plane.     

Synthesis of substituted 2-ethyl-3-(4-hydrazinocarbonylphenyl)-4-quinazo-lones and 2-ethyl-3-(4-hydrazinocarbonylmethylphenyl)-4-quinazolones

Some substituted 2-ethyl-3-(4-hydrazinocarbonylphenyl)-4-quinazolones and 2-ethyl-3-(4-hydrazinocarbonylmethylphenyl)-4-quinazolones were synthesized and characterized by their sharp melting points, elemental analyses and spectral data.     

Dual control mechanism in a Belousov-Zhabotinskii (B-Z) oscillator with glucose and oxalic acid as a double substrate

Oscillations in a Belousov-Zhabotinskii (B-Z) system having oxalic acid (OA) and glucose (G) as a mixed organic substrate, neither of which acts as a bromine scavenger, have been investigated. Studies have been performed for (i) varying the concentration of G while keeping the OA concentration fixed and (ii) varying OA but keeping G fixed in a batch reactor. In both cases upper and lower critical limits occur, between which oscillations are observed. Both single and double frequency oscillations have been observed in a wide range of concentrations of G as well as of OA. The induction period in most of the cases was <1 min. When G is fixed and OA is varied, the time pause between the sequential oscillations increases with an increase in OA. On the other hand when OA is fixed and G is varied, the time-pause decreases with an increase in G. The first type of oscillation is Br(-)-controlled, whereas the second is non-Br(-)-controlled. The order of addition of G and OA in the last has no influence on the induction period. It influences, however, the oscillatory characteristics. Br(2) evolution in the G + OA + Ce(4+) + BrO(3)(-) + H(2)SO(4) reaction system has been investigated spectrophotometrically. ESR and polymerization studies indicate the important role of free radicals in influencing the reaction mechanism. A tentative dual control mechanism has been suggested involving autocatalysis of HBrO(2) and BrO2*.     

Direct determination of large in-plane strains using high-resolution moiré shearography

A high-resolution moiré shearography method is described which allows direct measurement of in-plane strain and in-plane shearing strain.     

Kinetic determination of trace amounts of thiosulfate based on its inhibitory effect

The sulfur containing ligand viz., thiosulfate is found to inhibit the Ag(I) catalyzed substitution of cyanide in hexacyanoferrate(II) by phenylhydrazine. The inhibitory effect of thiosulfate is attributed due to its tendency to form complexes with Ag(I), leading to the production of inhibitor-catalyst complexes. The reactions, followed spectrophotometrically in aqueous medium at 488 nm, was possible by the increase in absorbance of the cherry-red product, [Fe(CN)₅PhNHNH₂]^3- at pH 2.8 (±0.02), at 30 (±0.1) °C, and an ionic strength (μ) of 0.02 M (KNO₃). The linear calibration curves were obtained using the absorbance measured at different times (A_t) and thiosulfate concentrations under specified conditions. The calculated detection limit was 4.9 × 10^-7 M. The Michaelis-Menten constant (K_m) and equilibrium constants for the formation of complexes between catalyst and inhibitor (K_CI), and the catalyst and substrate (K_S) were computed from the kinetic data. A general mechanistic scheme is proposed for this reaction.