Syntheses of Some 3—[1′（1′H）—Substituent—pyrazol—5′—yl] benzo [5,6] coumarins

3-[1′(1′H)-Substituent-pyrazol-5′-yl]benzo[5,6]coumarins and 3-(1′,2′-oxazol-5′-yl)benzo[5,6]coumarin were prepared via condensation of 3-(2′-formyl-1′-chlorovinyl)benzo[5,6] coumarin with hydrazine derivatives or hydroxylamine.Reaction of 3-[1′(1′H)-pyrazol-5′-yl]benzo[5,6]coumarin with alkyl halides,olefinic compunds or acid chlorides are described.     

Isolation of bioactive allelochemicals from sunflower (variety Suncross-42) through fractionation-guided bioassays

Plants are rich source of biologically active allelochemicals. However, natural product discovery is not an easy task. Many problems encountered during this laborious practice can be overcome through the modification of preliminary trials. Bioassay-directed isolation of active plant compounds can increase efficiency by eliminating many of the problems encountered. This strategy avoids unnecessary compounds, concentrating on potential components and thus reducing the cost and time required. In this study, a crude aqueous extract of sunflower leaves was fractionated through high performance liquid chromatography. The isolated fractions were checked against Chenopodium album and Rumex dentatus. The fraction found active against two selected weeds was re-fractionated, and the active components were checked for their composition. Thin layer chromatography isolated a range of phenolics, whereas the presence of bioactive terpenoids was confirmed through mass spectroscopy and nuclear magnetic resonance spectroscopy.     

A subdivision collocation method for solving two point boundary value problems of order three

In this paper, we propose a method for the numerical solution of self adjoint singularly perturbed third order boundary value problems in which the highest order derivative is multiplied by a small parameter $\varepsilon$. In this method, first we introduce the derivatives of two scale relations satisfied by the subdivision schemes. After that we use these derivatives to construct the subdivision collocation method for the numerical solution of singularly perturbed boundary value problems. Convergence of the subdivision collocation method is also discussed. Numerical examples are presented to illustrate the proposed method.     

Pyrolysis mechanism of trisbipyridineiron(II) chloride to iron nanoparticles

Pyrolysis of trisbipyridineiron(II) chloride under controlled thermal conditions and inert atmosphere of argon gas yields a residue of iron nanoparticles. Evolved gas analysis by GC?CMS and ¹H NMR revealed emission of bipyridine, 6-chlorobipyridine, 6,6??-dichlorbipyridine, bipyridine hydrochloride, and hydrochloric acid as decomposition products. CHN, XRPD, EDXRF, TEM, AFM, and ⁵⁷Fe M?ssbauer spectroscopy of the residue indicated formation of pure iron nanoparticles in the size range of 50?C72?nm. Based on these results a mechanism for thermal degradation of trisbipyridineiron(II) chloride has been worked out.     

Introducing Heterogeneity into the Micro-Scratch Test Fracture Toughness Relation for Brittle Particle Composites

Existing analysis methods of scratch test data are limited in their application to composite materials since they are built on the assumption of homogeneous material. In this study, the heterogeneity of the composite material is considered for analysis of scratch data on a resin and glass bead particle composite. Experiments are conducted using two approaches: macroscale three-point single edge notch and micro-scratch. An analysis method is presented which introduces a region in front of the crack tip to calculate the energy release rate during the fracture process which accounts for the heterogeneity of this region. By comparing with the experimental results, it is observed that this analysis method reduces the difference in fracture toughness derived from macroscale and microscale tests, and matches the trend of fracture toughness values as a function of particle volume fraction. This observation provides the insight that the local microstructure of the material needs to be considered in the scratch test analysis of particle composites.