Time‐Resolved Phase Transitions of the Nanocrystalline Cubic to Submicron Monoclinic Phase in Mn2O3‐ZrO2

The nanocrystalline cubic phase of zirconia was found to be thermally stabilized by the addition of 3 to 40 mol % manganese. The nanocrystalline cubic, tetragonal and monoclinic phases of zirconia stabilized with manganese (III)oxide (Mn‐Stabilized Zirconia) were prepared by thermal decomposition of carbonate and hydroxide precursors. Both the crystallization and isothermal phase transitions associated with Mn‐SZ were studied using high temperature x‐ray diffraction and x‐ray diffraction of quenched samples. Cubic Mn‐SZ initially crystallized and progressively transformed to tetragonal, and monoclinic structures above 700°C. The nanocrystalline cubic Mn‐SZ containing 25 mol % Mn was found to have the greatest thermal stability, retaining its cubic form at temperatures as high as 800°C for periods up to 25 hours. Higher than 40 mol %, cubic Mn₂O₃ was found to coexist with cubic Mn‐SZ. The crystallite sizes observed for the cubic, tetragonal and monoclinic Mn‐SZ phases ranged from 50 to 137, 130 to 220, and 195 to 450 Å respectively, indicating, for ZrO₂, that particle size was a primary factor in determining its polymorphs. The classical Avrami equation for nucleation and growth was applied to the observed phase transformations.     

Synthesis and antibacterial evaluation of several novel tripod pyrazoline with triazine core (TPTC) compounds

Research on Chemical Intermediates - A series of new thiocarbamoyl tris-pyrazoline (tripod pyrazoline with triazine core) compounds was obtained by tris-cyclization of chalcone with...     

A simple plasticity model for prediction of non-coaxial flow of sand

A bounding surface plasticity model for non-coaxiality, another aspect of anisotropic behavior of sands under rotation of principal stress axes; is developed in the critical state framework. Numerous experimental evidences exist that corroborate dependence of plastic shear strain rate direction on inherent fabric anisotropy. At first, general expressions for plastic strain rate with respect to possible emerge of non-coaxial flow are obtained. Consequently, using an anisotropy state parameter that is specially developed for this model and accounts for the interaction between imposed loading and soil fabric; effect of anisotropy on plastic flow direction is taken into account. Besides, novel circumstances are proposed for plastic modulus and dilatancy under rotation of principal stress axes. Finally, it is shown that the model is able to simulate successfully the non-coaxial behavior of sands subjected to principal stress axes rotation.     

Cooperativity effects of intramolecular OH…O interactions on pKa values of polyolalkyl sulfonic acids in the gas phase and solution: a density functional theory study

Density functional theory method and B3LYP/6‐311++G(d,p) level of theory were used to determine the acidity of alkyl sulfonic acids and polyolalkyl sulfonic acids in the gas and solution (H₂O, DMSO, and CH₃CN) phase. Polarized continuum model was applied to calculate pK_a values of alkyl sulfonic acids and polyolalkyl sulfonic acids. A comparison between acidity of alkyl sulfonic acids and polyolalkyl sulfonic acids in the gas and solution phase indicates that the acidity strength of polyolalkyl sulfonic acids enhances with the increase of the cooperativity effect of intramolecular hydrogen bonds in polyolalkyl sulfonic acids. Natural bond orbital and quantum theory of atoms in molecules analyses also confirm the role of cooperativity effect on the acidity of polyolalkyl sulfonic acids. Copyright © 2014 John Wiley & Sons, Ltd.     

Novel,One-Pot,Three-Component,Regioselective Synthesis of Fluorine-Containing Thiazole and Bis-3H-thiazole Derivatives Using Polyvinyl Pyridine as Heterogeneous Catalyst,and Evaluation of Their Antibacterial Activity

A convenient, one-pot, three-component regioselective synthesis of novel 2,2′-(1,4-phenylene)-bis-(3-aryl-2-substituted imino-4-aryl-3H-thiazole) derivatives from 1,4-phenylene diisothiocyanate, aryl amines, and various phenacyl bromide, and also the regioselective synthesis of 3-alkyl-2-(aryl imino)-4-cyclopropyl-5-(2′-fluorophenyl)-thiazole derivatives from alkylisothiocyanate, aryl amines, and 2-bromo-2-(2-fluorophenyl)-1-cyclopropylethanone in the presence of poly-4-vinyl pyridine as heterogenous basic catalyst are described. This efficient method produced the products at room temperature with excellent yields (82–96%). The structures of all products were characterized by spectral and elemental analyses. The antimicrobial activity of the synthesized compounds was evaluated against Salmonella enterica, Micrococcus luteus, Bacillus subtilis, and Pseudomonas aeruginosa.     

Diastereoselective Ruthenium-Catalyzed Michael Addition of Indoles to Hormone Steroids: An Efficient Route to New Indole Derivatives

Diastereoselective conjugate 1,4-addition of indoles to α,β-unsaturated carbonyl compounds (hormone steroids) using Ru(III) as catalyst is reported. It was found that RuCl₃·nH₂O catalyzes the Michael addition of indoles to hormone steroids, providing new 3-alkylated derivatives in good to excellent yields.     

Application of perforated sheets to improve the efficiency of reactive profiled noise barriers

The scope of this paper is to study the performance of noise barriers treated with different diffusers with/without a perforated sheet. We investigated the barrier insertion loss using a 2D boundary element method (BEM). To obtain a better depth sequence, a Random Sequence Diffuser (RSD) was designed. The results clearly showed that employing a "RSD" instead of the most popular Schroeder diffusers (Quadratic Residue Diffuser and Primitive Root Diffuser) increased the acoustic performance. We also found that the diffuser performance improved by treating the diffuser with perforated sheets either on the top surface or inside the wells. The addition of these perforated sheets inside the "RSD" (barrier model "RPI2") improved the performance by 3.59 dB (A).     

Digital broadband linearization technique and its application to photonic time-stretch analog-to-digital converter

Suppression of distortion induced by nonlinearity in a dynamical system (such as an analog optical link) is very challenging, particularly for a wide-bandwidth signal. Conventional compensation techniques are computationally intensive, significantly limiting their realization in real-time applications. Here, we propose and demonstrate an efficient digital postprocessing technique to suppress distortions added to a wideband signal by a nonlinear system with memory effect. Experimentally, digital broadband linearization of the photonic time-stretch analog-to-digital converter (TSADC) is demonstrated. In case of TSADC, a dynamic range improvement of >15 dB compared to conventional memory-less correction method is achieved.     

One-pot synthesis of novel pyrido[2,3-d]pyrimidines using HAp-encapsulated-γ-Fe2O3 supported sulfonic acid nanocatalyst under solvent-free conditions

Novel pyrido[2,3-d]pyrimidine derivatives were synthesized through a one-pot three-component approach using HAp-encapsulated-γ-Fe2O3[γ-Fe2O3@HAp-SO3H]catalyzed condensation of 6-arnino-2-（methylthio or ethylthio）pyrimidin-4（3H）-one,Meldrum＇s acid and aryl aldehydes at 60 ℃ and under solvent-free conditions.In this protocol the use of nanocatalyst provided a green,useful and rapid method to generate the products in short reaction times and excellent yields（88%-94%）.     

Efficient One-Pot Synthesis of Polyhydroquinoline Derivatives Using Silica Sulfuric Acid as a Heterogeneous and Reusable Catalyst Under Conventional Heating and Energy-Saving Microwave Irradiation

An efficient Hantzsch four-component condensation reaction for the synthesis of polyhydroquinoline derivatives was reported under two conditions: solvent-free conventional heating and energy-saving microwave irradiation. The process is simple and environmentally benign, and the use of a heterogeneous and reusable catalyst, high yields, and short reaction times are the key features of this protocol.