Pyridazine Derivatives and Related Compounds. Part 11: 1Synthesis of Some Pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazines

3-Substituted pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine-2,4-di-ones and 3-amino-2-methylpyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine-4-ones were synthesized starting from ethyl 5-aminothieno[2,3-c] pyridazine-6-carboxylate 1. Reaction of amino ester 1with phenyl isothiocyanate affords thiourea derivative 10which undergo further transformation to the related fused heterocyclic systems.     

Dielectric Properties of Colossal-Dielectric-Constant Na1/2La1/2Cu3Ti4O12 Ceramics Prepared by Spark Plasma Sintering

In the current study, we report on the dielectric behavior of colossal-dielectric-constant Na_1/2La_1/2Cu₃Ti₄O₁₂ (NLCTO) ceramics prepared by mechanochemical synthesis and spark plasma sintering (SPS) at 850 °C, 900 °C, and 925 °C for 10 min. X-ray powder diffraction analysis showed that all the ceramics have a cubic phase. Scanning electron microscope observations revealed an increase in the average grain size from 175 to 300 nm with an increase in the sintering temperature. SPS NLCTO ceramics showed a room-temperature colossal dielectric constant (>10³) and a comparatively high dielectric loss (>0.1) over most of the studied frequency range (1 Hz–40 MHz). Two relaxation peaks were observed in the spectra of the electrical modulus and attributed to the response of grain and grain boundary. According to the Nyquist plots of complex impedance, the SPS NLCTO ceramics have semiconductor grains surrounded by electrically resistive grain boundaries. The colossal dielectric constant of SPS NLCTO ceramics was attributed to the internal barrier layer capacitance (IBLC) effect. The high dielectric loss is thought to be due to the low resistivity of the grain boundary of SPS NLCTO.     

Possible two non-linear regions in the I–V characteristics of ZnO varistors

We report here structural and I–V characteristics of ZnO varistor with Fe₂O₃ nanoparticles additions (≤200 nm). It was found that the addition of Fe does not influence the wurtzite structure of ZnO ceramics, while the average grain size was affected. Interestingly, the nonlinear region was clearly observed in the I–V characteristics of the samples with Fe = 2.5%, 5% and 10%. Whereas, two nonlinear regions were only observed with further increase of Fe addition above 10% (30% and 50%). Although the values of non-linear coefficient are decreased by the additions of Fe, the breakdown field could be increased up to 7900 V/cm. Furthermore, the electrical conductivity was improved by increasing Fe up to 10%, followed by a decrease with further increase of Fe up to 50%. These results were discussed in terms of Fe₂O₃ nanosize grains which were formed and localized at the grain boundaries of ZnO ceramics.     

Voltammetric and spectroscopic studies on binding of antitumor Morin, Morin-Cu complex and Morin-beta-cyclodextrin with DNA

A systematic comparative study of the binding of antitumor Morin and its complexes with DNA has been investigated in the Britton-Robison (BR) buffer solutions using voltammetric and spectroscopic methods. The results show that Morin molecule, acting as an intercalator, is inserted into the cavity of the beta-cyclodextrin (beta-CD) as well as into the base stacking domain of the DNA double helix. The interaction of Morin-Cu complex or the inclusion complex of Morin-beta-CD with ds-DNA causes hypochromism in the absorption spectra, along with pronounced changes in the electrochemical behavior of the Morin complexes. An isobestic point and a new spectrum band appeared indicating the formation of the new system of Morin-Cu-DNA at lambda(m)=391 nm and Morin-beta-CD-DNA at lambda(m)=375 nm. The intercalation of Morin-Cu and Morin-beta-CD complexes with DNA produces an electrochemically inactive supramolecular complex. The binding constants were calculated from the increase of the solubility, the strong hypochromism, and the decrease in peak current of Morin and its complexes upon the addition of the host molecules. Calculation of the thermodynamic parameters of the interaction of the inclusion complex of Morin-beta-CD with DNA, including Gibbs free energy change, Helmholz free energy and entropy change shows that the complexation is a spontaneous process of association.     

Computational analysis of solitons all-optical logic NAND and XNOR gates using semiconductor optical amplifiers

Solitons all-optical logic NAND and XNOR gates using semiconductor optical amplifiers-assisted Mach–Zehnder interferometers are computationally analyzed at a data rate of 80 Gb/s. The investigation of the output quality factor is included. All-optical logic gates are capable of operating at 80 Gb/s with logical correctness and acceptable quality.     

Theoretical analysis of soliton NOR gate with semiconductor optical amplifier-assisted Mach–Zehnder interferometer

Optical and Quantum Electronics - We developed gigawatt laser system on diode-pumped Nd:Cr:YAG microchip sub-nanosecond laser and lamp pumped Nd:YAG multistage amplifier. Pulse energy up to...