One-pot,three-component,catalyst-free synthesis of novel derivatives of pyrido-[2,3-d]pyrimidines under ultrasonic irradiations

Novel derivatives of pyrido-[2,3-d] pyrimidines were synthesized via an efficient and catalyst- free, one-pot, three-component reaction of 3-(1-methyl-1H-pyrrol-2-yl)-3-oxopropanenitrile, 6-amino-(ethylthio)pyrimidine-4(3H)-one, and arylaldehydes under ultrasonic irradiations. This practical method furnished the desired pyridopyrimidines in high yields (79–89%) and short reaction times (25–40 min).     

N-Methylimidazolium perchlorate as a new ionic liquid for the synthesis of bis(pyrazol-5-ol)s under solvent-free conditions

N-Methylimidazolium perchlorate([MIm]ClO₄) was synthesized and some of its physico-chemical properties, such as density, surface tension were investigated. A thermo gravimetric analysis(TGA) and solvent performance were also studied. The results show that this ionic liquid is an excellent catalyst for the synthesis of 4,4'-(arylmethylene)bis(1H-pyrazol-5-ol) derivatives under solvent-free conditions. This method has the advantages of high yield, clean transformation, simple operation and short reaction time. The ionic liquid can be recycled without significant loss of activity.     

An efficient procedure for the synthesis of phenacyl and benzyl azolium salts using fluorous alcohols

An efficient procedure for the synthesis of phenacyl and benzyl azolium salts in 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoroisopropanol as fluorous alcohols have been developed. This synthetic methodology has some advantages with the respect to yield, atom efficiency, solvent and reagents used and wastes generated when compared to the currently in use methods. Using this procedure, a range of phenacyl and benzyl azolium salts can be synthesized with good to excellent yields. The pure salts are separated from the reaction mixture by simple filtration and washing with dry ether.     

Chaos after period-doubling bifurcations in the resonance of an impact oscillator

A linear, viscously damped oscillator that rebounds elastically whenever the displacement drops to zero is a well-defined quasi-linear deterministic system arising throughout the physical sciences. It exhibits a family of sub-harmonic resonant peaks between which we delineate cascades of period-doubling bifurcations leading to chaotic regimes typical of a strange attractor.     

Prediction of rheological behavior of MWCNTs–SiO2/EG–water non-Newtonian hybrid nanofluid by designing new correlations and optimal artificial neural networks

In this paper, at the first, new correlations were proposed to predict the rheological behavior of MWCNTs–SiO₂/EG–water non-Newtonian hybrid nanofluid using different sets of experimental data for the viscosity, consistency and power law indices. Then, based on minimum prediction errors, two optimal artificial neural network models (ANNs) were considered to forecast the rheological behavior of the non-Newtonian hybrid nanofluid. One hundred and ninety-eight experimental data were employed for predicting viscosity (Model I). Two sets of forty-two experimental data also were considered to predict the consistency and power law indices (Model II). The data sets were divided to training and test sets which contained respectively 80 and 20% of data points. Comparisons between the correlations and ANN models showed that ANN models were much more accurate than proposed correlations. Moreover, it was found that the neural network is a powerful instrument in establishing the relationship between a large numbers of experimental data. Thus, this paper confirmed that the neural network is a reliable method for predicting the rheological behavior of non-Newtonian nanofluids in different models.