Modeling advanced high-strength steels based on direct micro-macro calculations

Advanced high strength steels have immense commercial applicability today owing to the good combination of strength and ductility they offer. These properties mainly result from interactions of micro-heterogeneities leading to a complex macroscopic material behavior. One of these steels is the Dual Phase (DP) steel which has a microstructure consisting of two phases: ferrite (matrix material) and martensite (inclusion material). This paper proposes a technique to model the post-production situation of these steels, which is characterized by distributed material properties as well as eigenstresses. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of different types of epoxide-based Mannich polyols from low-cost cashew nut shell liquid

Cashew nut shell liquid (CNSL) is a natural aromatic organic oil consisting of phenolic compounds with interesting structures. Extraction of CNSL was performed in a Soxhlet apparatus. The major (90 %) component of CNSL is anacardic acid, which is easily decarboxylated to cardanol (10 %) by use of conventional methods. In this paper we describe a three-step synthesis of Mannich polyols for rigid foams. The first step is synthesis of N-(2-hydroxyethyl)-1,3-oxazolidine (the Mannich precursor) by condensation of paraformaldehyde and diethanolamine. The second step involves synthesis of the Mannich base phenolic ring of cardanol by reaction with N-(2-hydroxyethyl)-1,3-oxazolidine. The third step is alkoxylation. The synthesized polyols were characterized by FTIR and ¹H NMR spectroscopy and thin-layer chromatography.     

Ionomeric interpretation of thickening of polyesters by alkaline earth metal oxides

Four resins of poly(propylene glycol adipate) were mixed with different amounts of MgO and their viscosities were measured after a month. The viscosities increased by several thousand but the increase was less for resins containing more water. The existing explanations of the thickening behavior, namely the polymerization and the coordinate complex formation theories, were found to be inadequate in accounting for the observations. Small-angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) of the thickened resins revealed formation of aggregates of magnesium ions, much like those observed in other ionomers. It is postulated that domain formation is the cause of observed thickening. A correlation between the viscosity of thickened resins and the amount of metal oxide reacted, the water content, and other properties of resin was obtained.     

Highly regio- and stereoselective synthesis of tricyclic frameworks using Baylis-Hillman derivatives

A simple and convenient synthetic route for the synthesis of tricyclic chromeno[4,3-b]pyrrolidine frameworks using Baylis-Hillman bromides involving in situ formation of an imine, decarboxylation and a [3+2] cycloaddition sequence is described.     

Spectrophotometric and reversed-phase high-performance liquid chromatographic methods for simultaneous determination of escitalopram oxalate and clonazepam in combined tablet dosage form

Simple, accurate, precise, and sensitive ultraviolet spectrophotometric and reversed-phase high-performance liquid chromatographic (RP-HPLC) methods for simultaneous estimation of escitalopram oxalate (ESC) and clonazepam (CLO) in combined tablet dosage form have been developed and validated. The spectroscopic method employs an absorbance correction method using 238.6 and 308 nm as 2 wavelengths for estimation with methanol and water as solvents. Beer's law is obeyed in the concentration range of 10.0-50.0 and 0.5-3.0 micro/mL for ESC and CLO, respectively. The RP-HPLC method uses a Jasco HPLC system with HiQ SiL C18 column (250 x 4.6 mm id) acetonitrile-0.005 M tetrabutylammonium hydrogen sulfate (55 + 45, v/v) as the mobile phase, and satranidazole as an internal standard. The detection was carried out using an ultraviolet detector set at 287 nm. For the HPLC method, Beer's law is obeyed in the concentration range of 10.0-60.0 and 0.5-3.0 microg/mL for ESC and CLO, respectively. Both methods have been successfully applied for the analysis of the drugs in a pharmaceutical formulation. Results of analysis were validated statistically and by recovery studies.     

Column reversed-phase high-performance liquid chromatographic method for simultaneous determination of rabeprazole sodium and domperidone in combined tablet dosage form

A new, simple column reversed-phase high-performance liquid chromatographic (HPLC) method for simultaneous determination of rabeprazole sodium (RAB) and domperidone (DOM) in a combined tablet dosage form has been developed and validated. Determination was performed using a Jasco HPLC system with a HiQ SiL octadecylsilane (C18) column (250 x 4.6 mm id), acetonitrile-0.1 M ammonium acetate (50 + 50, v/v) mobile phase, and paracetamol as an internal standard. The detection was performed using a UV detector set at 280 nm. The method was validated with respect to linearity, accuracy, precision, and robustness. Beer's law was obeyed in the concentration range of 1.0-10.0 and 0.5-5.0 microg/mL for RAB and DOM, respectively. The method has been successfully applied for the analysis of drugs in a pharmaceutical formulation.     

Synthesis of chiral organocatalysts derived from aziridines: application in asymmetric aldol reaction

We report the synthesis of a new series of highly efficient chiral organocatalysts derived via the regio- and stereoselective ring opening of chiral aziridines with azide anions. The catalysts have proved to be very efficient for a direct asymmetric aldol reaction, both with cyclic as well as acyclic ketones in brine with 2 mol % of catalyst loading, and afforded the products in excellent yields (up to 99%) and enantioselectivities (up to >99%). The chiral aldol adduct obtained has further been converted to a chiral azetidine ring via a convenient pathway.     

Synthesis of novel 2,4,6-trisubstituted pyrimidine derivatives and their in vitro antimicrobial activity

A series of novel pyrimidines (6a–6i) has been synthesized from corresponding chalcones and isonicotinimidamide.HCl in the presence of potassium carbonate involving Michael addition followed by cycloaddition. All newly synthesised chalcones and pyrimidines were screened for in vitro antimicrobial activity against various Gram positive, Gram negative bacterial and fungal strains. Most of compounds displayed high antimicrobial activity compared to standard drugs Penicillin, Streptomycin and Ampothericin-B.     

Measurement of sodium ion concentration in undiluted urine with cation-selective polymeric membrane electrodes after the removal of interfering compounds

The measurement of sodium ion concentration in urine can provide diagnostic information and guide therapy. Unfortunately, neutral-carrier-based ion-selective electrodes show a large positive drift and loss in selectivity in undiluted urine. The extraction of electrically neutral lipids from the urine into the sensing membrane was suggested as the main source of the drift, loss of selectivity and the consequent incorrect concentration readings.In this work, (i) solvent-solvent extraction, (ii) membrane-immobilized solvent extraction and (iii) solid phase extraction were used to remove interfering compounds from urine samples. The “cleaned” urine samples were subsequently analyzed using a calixarene (sodium ionophore X)-based, solid-contact, sodium-selective electrode in a flow-through manifold. The solid-contact sodium sensors had excellent stability in cleaned urine and an acceptable bias compared to commercial clinical analyzers.