Domino Michael-Aldol reactions on 1,4-diarylbut-2-ene-1,4-diones with methyl acetoacetate furnish methyl 2-aroyl-4- hydroxy-6-oxo-4-arylcyclohexane-1-carboxylate derivatives

Domino Michael-Aldol reactions on 1,4-diaryl-2-butene-1,4-diones with methyl acetoacetate in the presence of activated Ba(OH)(2) furnished methyl (1R*,2S*,4S*)-2-aroyl-4-hydroxy-6-oxo-4-arylcyclohexane-1-carboxylate derivatives in a stereo- and regiospecific manner. While treatment of these cyclohexanecarboxylate products with TsOH resulted in the dehydrated and decarbomethoxylated cyclohexenone derivatives, the reaction with NaOMe furnished 3,5-disubstituted phenols via dehydration, decarbomethoxylation, and dehydrogenation. NaCl/DMSO under microwave irradiation transformed the cyclohexanecarboxylate products to the 7-hydroxyisobenzofuranone derivatives.     

Ultrasound mediated alkaline hydrolysis of methyl benzoate--reinvestigation with crucial parameters

In the present work hydrolysis of methyl benzoate was carried out using aqueous sodium hydroxide solution at room temperature in the presence of ultrasound since otherwise the same reaction takes place at relatively high temperature. Also, the above hydrolysis reaction was investigated at a relatively larger scale with the variation in parameters influencing the emulsification process and hence the reaction rates. It has been observed that the position of ultrasound source on the liquid-liquid interface is a crucial parameter affecting the two-phase emulsification rates. The poor bulk mixing occurring in the presence of ultrasound alone with an increase in the volume of the reaction mixture and its consequent effect on the reaction kinetics has been conclusively established. These studies have shown that the use of ultrasound with mechanical stirring can result in substantial reduction in the overall power consumption, especially for reaction systems like hydrolysis that do not require very high temperatures and pressures generated by cavitation.     

Synthesis and Characterization of SnO2 Nanopowder Prepared by Precipitation Method

Tetragonal SnO₂ nanopowder of the range ～8 nm has been successfully synthesized by precipitation method. The prepared powder was characterized by thermogravimetry analysis (TGA), x-ray diffraction (XRD), transmission electron microscopy (TEM), Infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), and room temperature photoluminescence (PL) spectroscopy. Experimental results show that the prepared powder was phase pure SnO₂ of tetragonal rutile structure without any impurities. The optical band gap was determined to be 4.26 eV, using diffuse reflectance technique with the aid of Kubelka-Munk relation. The blue shift of the band gap was attributed to the quantum size confinement effect.     

Key role of time-delay and connection topology in shaping the dynamics of noisy genetic regulatory networks

This paper focuses on a paced genetic regulatory small-world network with time-delayed coupling. How the dynamical behaviors including temporal resonance and spatial synchronization evolve under the influence of time-delay and connection topology is explored through numerical simulations. We reveal the phenomenon of delay-induced resonance when the network topology is fixed. For a fixed time-delay, temporal resonance is shown to be degraded by increasing the rewiring probability of the network. On the other hand, for small rewiring probability, temporal resonance can be enhanced by an appropriately tuned small delay but degraded by a large delay, while conversely, temporal resonance is always reduced by time-delay for large rewiring probability. Finally, an optimal spatial synchrony is detected by a proper combination of time-delay and connection topology.     

Structural,optical, and charge transport properties of cyclopentadithiophene derivatives: a theoretical study

Density functional theory calculations were carried out to investigate the structural and opto-electronic properties of cyclopenta[2,1-b:3,4-b′]dithiophene (CPDT) derivatives. The ground state, cationic and anionic geometries of cyclopentadithiophene derivatives were optimized at B3LYP/6-311G(d,p) level of theory. Based on these geometries, ionic state properties such as ionization potentials, electron affinities, hole extraction potential, and electron extraction potential of cyclopentadithiophene derivatives have been calculated. The charge transfer integral, spatial overlap integral, and site energy were calculated from the matrix elements of Kohn–Sham Hamiltonian. Computed results show that the mobility of charge carriers in CPDT derivatives is strongly affected by the substitution of electron withdrawing group at bridge-head and α-positions. The excited state geometry of CPDT derivatives were optimized using configuration interaction singles method. On the basis of ground and excited states geometry, absorption and emission spectra of cyclopentadithiophene derivatives were calculated using the time-dependent density functional theory method. It has been observed that the substitution of EWG in cyclopentadithiophene core alters the absorption and emission spectra. The nonlinear optical property of CPDT derivatives have been studied through computed static polarizability and first hyperpolarizability.     

Structural and optical behavior of SnS2/NiFe2O4 NCs prepared via novel two-step synthesis approach for MB and RhB dye degradation under sun light irradiation

The present investigation focuses on facile two-step synthesis approach fabrication of tin sulfide (SnS₂)/ nickel ferrite (NiFe₂O₄) nanocomposites (NCs) for the first time. The crystallinity and phase purity of the prepared material was investigated in powder X-ray diffraction (PXRD) studies. The presence of functional groups (stretching and bending vibration) was primarily determined by the Fourier Transform Infrared Spectroscopy (FT-IR) analysis. As well as, optical behavior of the synthesized samples was determined in UV–Vis absorption spectroscopic studies, and the presence of surface defects was established by PL spectroscopic studies. From the FESEM analysis, sponge-like structure was attained and Ni, Fe, Sn, S and O elemental component was determined by the EDAX spectrum analysis. The as-prepared SnS₂/NiFe₂O₄ NCs exhibit superior photocatalytic performance and high stability toward the reduction of methylene blue (MB) and rhodamine B (RhB) dyes under irradiation of direct sunlight. The synthesized nanocomposites showed an efficient photocatalytic activity with a high reaction kinetic rate.

     

Determination and analysis of non-linear index profiles in electron-beam-deposited MgOAl2O3ZrO2 ternary composite thin-film optical coatings

Thickness-dependent index non-linearity in thin films has been a thought provoking as well as intriguing topic in the field of optical coatings. The characterization and analysis of such inhomogeneous index profiles pose several degrees of challenges to thin-film researchers depending upon the availability of relevant experimental and process-monitoring-related information. In the present work, a variety of novel experimental non-linear index profiles have been observed in thin films of MgOAl₂O₃ZrO₂ ternary composites in solid solution under various electron-beam deposition parameters. Analysis and derivation of these non-linear spectral index profiles have been carried out by an inverse-synthesis approach using a real-time optical monitoring signal and post-deposition transmittance and reflection spectra. Most of the non-linear index functions are observed to fit polynomial equations of order seven or eight very well. In this paper, the application of such a non-linear index function has also been demonstrated in designing electric-field-optimized high-damage-threshold multilayer coatings such as normal- and oblique-incidence edge filters and a broadband beam splitter for p-polarized light. Such designs can also advantageously maintain the microstructural stability of the multilayer structure due to the low stress factor of the non-linear ternary composite layers. PACS 78.20.Bh; 78.20.Ci; 77.55.+f; 81.15.Ef     

Correlation of optical and microstructural properties of Gd2O3 thin films through phase-modulated ellipsometry and multi-mode atomic force microscopy

Gadolinium oxide thin films have been prepared by electron beam evaporation with different reactive oxygen pressures at low ambient substrate temperature. These thin films have been analyzed with phase-modulated spectroscopic ellipsometry and multi-mode atomic force microscopy (AFM). The distinct influences of oxygen pressure on surface topographies, microstructures and refractive indices of the thin films have been observed from the results of these advanced measurements. Both these techniques have displayed very strong co-relationships in the characterisation results acquired through respective modes of measurements and data analysis. Unequivocally, these two techniques indicated an optimum value of the oxygen pressure leading to best optical and structural properties of such a novel optical coating material.