Modification of magnetic anisotropy in metallic glasses using high-energy ion beam irradiation

Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe₄₀Ni₄₀B₂₀ and Fe₄₀Ni₃₈Mo₄B₁₈ metallic glass ribbons. 90 MeV ¹²⁷I beam was used for the irradiations. Irradiation doses were 5×10¹³ and 7.5×10¹³ ions/cm². The relative intensity ratios D ₂₃ of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy.     

Synthesis of 3,6-epoxy[1,5]dioxocines from 2-hydroxyaromatic benzaldehydes

Convenient and facile one step synthesis of medicinally relevant new 3,6-epoxy[1,5]dioxocines from 2-hydroxyaromatic benzaldehydes is described. The scope of the method was validated by examining the use of both electron rich and electron-deficient 2-hydroxyaromatic benzaldehydes.     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.     

Magnetization curves for general cylindrical samples in a transverse field

Using the recent results for the surface current density on cylindrical surfaces of arbitrary cross-section producing uniform interior magnetic field we propose a method for obtaining solutions of Bean’s critical state model for general cylindrical samples. The method uses the technique of conformal mapping to express the sample surface and the flux-fronts in terms of a set of coefficients that depend on a parameter. The flux-fronts are to be determined by solving a system of nonlinear ordinary differential equations for the coefficients. Retaining only a certain finite number of leading coefficients we get an approximate solution. The procedure is illustrated by considering two cyclindrical samples — one with an elliptical cross-section and the other with a non-elliptical cross-section. The virgin curve and small and large magnetization hysteresis loops for the two samples are obtained.     

Low-field vortex dynamics in various high-T c thin films

We present a novel ac susceptibility technique for the study of vortex creep in superconducting thin films. With this technique we study the dynamics of dilute vortices in c-axis oriented Y-123, Hg-1212, and Tl-1212 thin films, as well as a axis oriented Hg-1212 thin films. Results on the Hg-1212 and Tl-1212 thin films indicate that dislocation-mediated plastic flux creep of single vortices dominates at low temperatures and fields. As the temperature (or the field) is increased, the increasing vortex-vortex interactions promote a collective behavior, which can be characterized by elastic creep with a non-zero μ exponent. Also, in some of these samples effects of thermally assisted quantum creep are visible up to 45 K in some of these samples. In Y-123 thin films, creep is found to be collective down to the lowest temperatures and fields investigated, while the quantum creep persists only up to 10–11 K.     

Identification of the antioxidant principles of Polyalthia longifolia var. pendula using TEAC assay

Activity-guided fractionation of the ethanolic extract of the leaves of the Polyalthia longifolia var. pendula led to the identification of quercetin (1), quercetin-3-O-β-glucopyranoside (2), kaempferol-3-O-α-rhamnopyranosyl-(1 → 6)-β-galactopyranoside (3), kaempferol-3-O-α-rhamnopyranosyl-(1 → 6)-β-glucopyranoside (4), rutin (5) and allantoin (6) as the active constituents from the butanol fraction. Compounds 2-4 are reported for the first time from this natural source. Structures of the compounds were confirmed on the basis of their 1D and 2D NMR coupled with other spectroscopic methods. All the isolated compounds and the fractions were evaluated for their antioxidant potential using the TEAC assays and it was found that the activity of the active fraction was due to quercetin (1) and its glycosides (2 and 5), with TEAC values of 4.10, 1.91 and 2.38 mM, respectively, while the kaempferol glycosides were found to be inactive. This is the first study on the antioxidant activity of this plant species.     

A novel route to synthesis of flavones from salicylaldehyde and acetophenone derivatives

Convenient, facile, and alternate synthesis of medicinally important flavones is reported. The 2-hydroxychalcones derived from condensation between acetophenones and salicylaldehyde, underwent oxidative cyclization on heating in the presence of catalytic iodine, generating diversified flavones under solvent-free conditions. Eleven compounds have been synthesized in good to excellent yields and their mechanism of formation is described.     

Simultaneous estimation of 16α-hydroxycleroda-3,13(14) Z-dien-15,16-olide from Polyalthia longifolia and its metabolite in hamster plasma: application to pharmacokinetic study

A selective and sensitive LC–MS‐MS method was developed and validated for simultaneous estimation and pharmacokinetic studies of 16α‐hydroxycleroda‐3,13(14) Z‐dien‐15,16‐olide (K‐09) obtained from Polyalthia longifolia and its metabolite (K‐9T), a novel antidyslipidemic agent. Sample clean‐up involved liquid–liquid extraction of both the analytes and internal standard (rosuvastatin) from 200 μL of hamster plasma. The analytes were chromatographically separated on a Symmetry‐Shield C₁₈ (5 µm, 4.6 × 150 mm) column, using acetonitrile–0.1% aqueous formic acid (92:08, v/v) as the mobile phase. Detection was performed using negative ion electrospray ionization in multiple reaction monitoring mode. The MS/MS response was linear over the concentration range 1.56–200 ng/mL, with a correlation coefficient (r²) of 0.998 or better. The within‐ and between‐batch precisions (relative standard deviation, %RSD) and the accuracy (percentage bias) were within acceptable limits as per FDA guidelines. The validated method was successfully applied to reveal the pharmacokinetic parameters of K‐09 and metabolite after oral administration. This method will therefore be highly useful for future studies of K‐09 and metabolite K‐9T pharmacokinetics in preclinical and clinical studies. Copyright © 2011 John Wiley & Sons, Ltd.     

A facile and efficient Bi(III) catalyzed synthesis of 1,1-dihydroperoxides and 1,2,4,5-tetraoxanes

Bismuth triflate is a remarkably efficient and mild catalyst for the synthesis of both 1,1-dihydroperoxides and 1,2,4,5-tetraoxanes. The successful application of this methodology for the synthesis of both symmetrical and unsymmetrical tetraoxanes is demonstrated.     

Base promoted peroxide systems for the efficient synthesis of nitroarenes and benzamides

A useful and efficient approach for the synthesis of nitroarenes from several aromatic amines (including heterocycles) using peroxide and base has been developed. This oxidative reaction is very easy to handle and afforded the products in good yields. Formation of benzamides from benzylamine was also successfully carried out with this metal-free catalytic system in good to excellent yields.