Influence of bromoalkyloxy side chain on mesomorphic behavior in heterocyclic 7-(4-bromoalkyloxy)-3-(4′-decyloxyphenyl)-4H- 1-benzopyran-4-ones

A new homologous series of isoflavone-based ethers,7-(4-bromoalkyloxy)-3-(4’-decyloxyprienyl)-4H-1-benzopyran-4-ones were synthesized and characterized.The mesomorphic properties of all homologues were investigated by differential scanning calorimetry(DSC) and polarizing optical microscopy(POM).Enantiotropic smectic A(SmA) phase was observed for all homologues.The structure-property study was carried out by comparing the mesomorphic behavior of the homologues with those previously reported analogues.The bromine atom from the alkyloxy side chain of the benzene ring fused to the heterocyclic moiety was found to be capable of changing the mesomorphic properties.     

Effect of tellurium promoter on vanadium phosphate catalyst for partial oxidation of n-butane

Te-promoted (1%) vanadium phosphate catalyst (VPDTe) was prepared via VOPO4·2H2O by calcining its precursor VOHPO4·0.5H2O in a flow of n-butane/air.VPDTe catalyst has resulted a higher existence of V5+ phase with V5+/V4+ ratio of 0.23.SEM micrographs show that Te addition altered the arrangement of the platelets from "rose-like" clusters to layer with irregular shape.Te addition has also markedly lowered the reduction activation energies of the vanadium phosphate catalyst as revealed by TPR profile.The amount of active oxygen species associated with V4+ phase of the Te promoted catalyst was significantly higher than those of the unpromoted catalyst.These observations suggest that high mobility and availability of reactive oxygen species contributed to the enhancement of n-butane conversion up to 80% at 673 K,while only 47% over unpromoted catalyst (2400 h-1,1.7% n-butane in air).     

Dealuminated ZSM-5 Zeolite Catalyst for Ethylene Oligomerization to Liquid Fuels

Ethylene oligomerization using ZSM-5 zeolite was investigated to study the role of Bronsted acid sites in the formation of higher hydrocarbons. The oligomerization of olefins, dependent on the acidity of ZSM-5 zeolite, is an important step in the conversion of natural gas to liquid fuels. The framework Si/Al ratio reflects the number of potential acid sites and the acid strength of the ZSM-5 catalyst. ZSM-5 with the mole ratio SiO2/Al2O3 equal to 30 was dealuminated for different periods of time according to the acidic ion-exchange method to produce ZSM-5 with various Si/Al ratios. The FT-IR analysis revealed that the integrated framework aluminum band, non-framework aluminum band, and silanol groups areas of the ZSM-5 zeolites decreased after being dealuminated. The performance of the dealuminated zeolite was tested for ethylene oligomerization. The results demonstrated that the dealumination of ZSM-5 led to higher ethylene conversion, but the gasoline selectivity was reduced compared to the performance     

Effect of formulation of alginate beads on their mechanical behavior and stiffness

The aim of this work was to determine the effect of formulation of alginate beads on their mechani-cal behavior and stiffness when compressed at high speed. The alginate beads were formulated using different types and concentrations of alginate and gelling cations and were produced using an extrusion-dripping method. Single wet beads were compressed at a speed of 40 mm/min,and their elastic limits were investigated,and the corresponding force versus displacement data were obtained. The Young's moduli of the...     

Realization of a low threshold multiwavelength brillouin/erbium fiber laser by optimizing the reflected power

A multiwavelength Brillouin/erbium fiber laser (BEFL) with low threshold power is realized. A low threshold power of 3 mW and a wide tuning range of 18 nm can be achieved by controlling the reflected power in the nonlinear optical loop mirror (NOLM). Up to 24 lines with a wavelength spacing of 0.086 nm are generated at the Brillouin pump and at the 1 480-nm pump with 0.5 dBm (0.9 mW) and 25 mW of power, respectively.     

Nematogenic and smectogenic liquid crystals from new heterocyclic isoflavone derivatives:Synthesis,characterization and X-ray diffraction studies

A new series of liquid crystals comprising eight heterocyclic isoflavone esters,7-alkanoyloxy-3-[4’-(3-methylbutyloxyphenyl)]- 4H-1-benzopyran-4-ones exhibiting enantiotropic nematic(N) and smectic C(SmC) phases were synthesized and investigated.The mesomorphic properties of all derivatives were investigated by means of differential calorimetry and polarized optical microscopy. Wide angle X-ray diffraction technique was employed to investigate the molecular packing associated with the intermolecular interaction as well as the correlation between the thermal behaviour of these compounds with their anisotropy properties within a mesophase.     

New mesogenic Schiff base esters comprising benzothiazole moiety： Synthesis and mesomorphic properties

A homologous series of Schiff base esters,6-methoxy-2-(2-hydroxy-4-alkanoyloxybenzylidenamino)benzothiazoles,comprising a benzothiazole moiety as the core was synthesized.All the members of this series exhibited an enantiotropic nematic phase. The azomethine linkage along with the lateral hydroxyl and terminal methoxyl groups were found to exert an effect on the mesomorphic properties.     

Spectral hole burning effects initiated by uniform signal intensities in a gain-flattened EDFA

Spectral hole burning (SHB) effects in a gain-flattened erbium-doped fiber amplifier (EDFA) are demonstrated to be significant in the presence of large signal power around the 1530-1532-nm wavelength range. These are the first effects reported in a setup employing equivalent power level distribution of 40 channels ranging from 1530 to 1561 nm. To explain this, the introduction of a new local population variable into the laser equation is required to support the original inversion ratio that is determined by the pump lasers. In the analysis section, spectroscopic parameters and high signal powers are considered to be other contributing parameters to the change in the gain characteristics. An improvement to this theoretical basis is suggested by implementing mathematical modeling to validate similarities between the gain shape of simulation to that obtained in the experiment.