Young measure solutions and instability of the one-dimensional Perona-Malik equation

We apply a variational approach to the one-dimensional version of the widely used Perona-Malik equation in image processing. We rephrase the problem into the one related to the quasiconvex hull of a graph in the space of 2×2 matrices M2×2. We then use the solutions of some heat equations as the centre of the mass for the Young measure-valued solutions to construct the approximate solutions by using simple laminates. The approximate solutions can be viewed as solutions of a perturbation problem by W−1,p (or W−1,∞) functions. The sequences of the approximate solutions generates Young measure-valued solutions. Our results also show that the solutions of the one-dimensional Perona-Malik equation are unstable under small W−1,∞ perturbations.     

Aqueous NaHSO4 catalyzed regioselective and versatile synthesis of 2-thiazolamines

The green acidic catalyst NaHSO₄ was used for the synthesis of some novel substituted 2-thiazolamines in water under mild conditions in high regioselectivity. Correspondence: Shahnaz Rostamizadeh, Department of Chemistry, Faculty of Sciences, K.N. Toosi University of Technology, P. O. Box: 15875-4416, Tehran, Iran.     

A novel and efficient synthesis of pyrazolo[3,4-d]pyrimidine derivatives and the study of their anti-bacterial activity

In this work 4-amino-6-aryl-2-phenyl pyrimidine-5-carbonitrile derivatives were synthesized through a one-pot,three-component reaction of an aldehyde,malononitrile and benzamidine hydrochloride,in the presence of magnetic nano Fe₃O₄ particles as a catalyst under solvent-free conditions.3-Amino-6-aryl- 2-phenylpyrazolo[3,4-d]pyrimidine derivatives were prepared through an efficient and environmentally friendly reaction between 4-amino-6-aryl-2-phenylpyrimidine-5-carbonitrile derivatives and hydrazine hydrate and their antibacterial activity has been evaluated.     

An Environmentally Benign Multicomponent Synthesis of Some Novel 2‐Methylthio Pyrimidine Derivatives Using MCM‐41‐NH2 as Nanoreactor and Nanocatalyst

Some novel 4‐amino‐6‐aryl‐2‐methylthio pyrimidine‐5‐carbonitrile derivatives were synthesized through a one‐pot three‐component reaction of an aldehyde, malononitrile, and S‐methylisothiouronium iodide, using MCM‐41‐NH₂ as nanoreactor and nanocatalyst. This protocol has some advantages including application of readily available and nonhazardous materials, benign reaction conditions (ambient temperature, solvent‐free, and one‐pot approach), easy work‐up, and high overall yields of the products.     

TG measurement of reactivity of candidate oxygen carrier materials

This study examined several candidate raw materials for use as the reactive agents in developing new oxygen carriers for chemical looping combustion. A thermogravimetric analyzer, Mettler TGA/DSC1, was used to measure oxygen capacity and relative reaction rates during oxidation and reduction cycles. The reactive gases used were 4 % hydrogen in inert gas for the reduction cycle and air for the oxidation cycle, with a nitrogen purge between reduction and oxidation cycles. Samples were typically tested for at least ten cycles to study any change in reactivity or oxygen capacity. Reaction temperatures tested ranged from 700 to 900 °C. Materials tested included an iron oxide ore, iron-based tailings from a metals extraction process, a nickel oxide supported on nickel aluminate and a copper oxide plus inert material system. The materials varied in their oxygen capacity, reactivity and the change in properties with repeat cycles. Of the samples tested, the NiO–NiAl₂O₄ oxygen carrier demonstrated the fastest reaction in reduction and oxidation and had stable properties over ten cycles. The iron oxide ore sample performance declined significantly with repeat cycles. The performance of the iron-based tailings declined slightly over the ten cycles. The addition of inert second phase materials to CuO improved the performance by inhibiting sintering of the oxide at the operating temperature. Although the reactivity of the tailings and iron hydroxide samples was not as high as the NiO based oxygen carrier, they are promising carrier materials due to their low cost and lower toxicity relative to nickel. Future experiments will look at CO and CH₄ reduction reactions using the TG, surface characterization using SEM, XRD, and cyclic testing in a batch fluidized bed reactor.     

A mild and highly efficient method for the synthesis of 5‐aryl‐(N‐phenyl‐)6H‐1,3,4‐thiadiazin‐2‐aminium salts using reusable heterogeneous catalysts

5‐Aryl‐6H‐1,3,4‐thiadiazin‐2‐aminium and 5‐aryl‐N‐phenyl‐6H‐1,3,4‐thiadiazin‐2‐aminium salts have efficiently been synthesized from the reaction of thiosemicarbazide and α‐haloketones in acetonitrile at room temperature using i) silica supported sodium hydrogen sulfate and ii) silica sulfuric acid as reusable heterogeneous catalysts. The experimental procedure is simple and the products are obtained in high yields.     

Piperidines: a new class of urease inhibitors

A variety of piperidines (2-12, 14-26) with variable substituents at N-atoms have been synthesized and evaluated as urease inhibitors. The synthesized compounds showed varying degree of urease inhibitory activity ranging from 31.97 to 254 microM. The size and electron-donating or -withdrawing effects of substituents influence the activity, which lead to the formation of urease inhibitors.     

Silica supported ammonium dihydrogen phosphate (NH4H2PO4/SiO2):A mild,reusable and highly efficient heterogeneous catalyst for the synthesis of 14-aryl-14-H-dibenzo[a,j]xanthenes

Silica supported ammonium dihydrogen phosphate (NH₄H₂PO₄/SiO₂) is found to be a recyclable heterogeneous catalyst for a rapid and efficient synthesis of various aryl-14-H-dibenzo[a,j]xanthenes with excellent yields under solvent-free conditions. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times and milder conditions.     

Inorganic Bergman Cyclization: An Appeal From Theory

The scope of Bergman cyclization is expanded computationally by exploring the cyclization in inorganic B, N substituted derivative. This substitution has introduced polarity into the transition state, which resulted in dramatic lowering of the activation barrier. Natural charge distribution throughout the reaction profile has ascertained this hypothesis. Single B and N atom substitution at 1 and 6 terminal positions lowers the activation barrier by almost half of the original value which becomes even lower in the complete B, N analogue. The parent Bergman and single B, N substituted products were characterized by significant biradical character while the complete B, N substituted analogue was characterized by significant zwitterionic character. Reduction in electron delocalization is also observed in the complete B, N substituted analogue.