Co-doped In2O3 thin films: Room temperature ferromagnets

Laser-ablated Co-doped In₂O₃ thin films were fabricated under various growth conditions on R-cut Al₂O₃ and MgO substrates. All Co:In₂O₃ films are well-crystallized, single phase, and room temperature ferromagnetic. Co atoms were well substituted for In atoms, and their distribution is greatly uniform over the whole thickness of the films. Films grown at 550 °C showed the largest magnetic moment of about 0.5 μ_B/Co, while films grown at higher temperatures have magnetic moments of one order smaller. The observed ferromagnetism above room temperature in Co:In₂O₃ thin films has confirmed that doping few percent of magnetic elements such as Co into In₂O₃ could result in a promising magnetic material.     

Reversible pressure deformation of a thermophilic cytochrome P450 enzyme (CYP119) and its active-site mutants

The pressure stability of the thermophilic CYP119 from Sulfolobus solfataricus and its active-site Thr213 and Thr214 mutants was investigated. At 20 degrees C and pH 6.5, the protein undergoes a reversible P450-to-P420 inactivation with a midpoint at 380 MPa and a reaction volume change of -28 mL/mol. The volume of activation of the process was -9.5 mL/mol. The inactivation transition was retarded, and the absolute reaction volume was decreased by increasing temperature or by mutations that decrease the size of the active-site cavity. High pressure affected the tryptophan fluorescence yield, which decreased by about 37% at 480 MPa. The effect was reversible and suggested considerable contraction of the protein. Aerobic decomposition of iron-aryl complexes of the CYP119 T213A mutant under increasing hydrostatic pressure resulted in variation of the N-arylprotoporphyrin-IX regioisomer (N(B):N(A):N(C):N(D)) adduct pattern from 39:47:07:07 at 0.1 MPa to 23:36:14:27 at 400 MPa. Preincubation of the protein at 400 MPa followed by complex formation and decomposition gave the same regioisomer distribution as untreated protein. The results indicate that the protein is reversibly inactivated by pressure, in contrast to the irreversible inactivation of P450(cam) and other P450 enzymes, and that this inactivation process is modulated by changes in the active-site cavity dimensions.     

Reversed-phase liquid chromatographic method for the analysis of aminoglycoside antibiotics using pre-column derivatization with phenylisocyanate

A pre-column derivatization liquid chromatographic method has been developed for the analysis of aminoglycoside antibiotics using phenylisocyanate as a derivatization reagent. Derivatives including kanamycin, neomycin and gentamicin were formed by reaction of the analytes with phenylisocyanate in the presence of triethylamine. Phenylisocyanato groups were attached to corresponding amino groups of aminoglycoside and their molecular mass was confirmed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). The experimental conditions for derivatization and separation of aminoglycoside derivatives were optimized and validated. A simple liquid chromatographic method for the determination of aminoglycoside antibiotics was demonstrated.     

Oliveridepsidones A–D,antioxidant depsidones from Garcinia oliveri

Four new prenylated depsidones, oliveridepsidones A–D, were isolated from the bark of Garcinia oliveri collected in Vietnam. Their structures were elucidated using mainly NMR techniques (¹H and ¹³C NMR, HMQC, HMBC and NOE experiments). Copyright © 2012 John Wiley & Sons, Ltd.     

Hopf bifurcation control via a dynamic state-feedback control

To relocate two Hopf bifurcation points, simultaneously, to any desired locations in n-dimensional nonlinear systems, a novel dynamic state-feedback control law is proposed. Analytical schemes to determine the control gains according to the conditions for the emergence of Hopf bifurcation are derived. To verify the effectiveness of the proposed control law, numerical examples are provided.     

THE REACTION OF TERMINAL PHOSPHINIDENE COMPLEXES WITH ELECTRON-RICH ALKYNES: A NEW APPROACH TO THE PHOSPHOLE RING

Abstract

The reaction of electron-rich alkynes such as ethoxyacetylene or propynyldiethylamine with a transient terminal phosphinidene complex such as [PhP?W(CO)₅] directly yields the corresponding phosphole complexes via a formal [2 + 2 + I] cycloaddition involving two molecules of alkyne and one phosphorus center.     

The effect of carbon nanotubes on epoxy matrix nanocomposites

The paper concerns thermal properties of epoxy/nanotubes composites for aircraft application. In this work, influence of carbon nanotubes on thermal stability, thermal conductivity, and crosslinking density of epoxy matrix was determined. Three kinds of nanotubes were used: non-modified with 1- and 1.5-μm length, and 1-μm length modified with amino groups. Scanning electron microscopy observations were done for examining dispersion of nanotubes in the epoxy matrix. Glass transition temperature (T _g) was readout from differential scanning calorimetry. From dynamic mechanical analysis, crosslinking density was calculated for epoxy and its composites. Also, thermogravimetric analysis was done to determine influence of nanotubes addition on thermal stability and decomposition process of composites. Activation energy was calculated from TGA curves by Flynn–Wall–Ozawa method. Thermal diffusivity was also measured. SEM images proved the uniform dispersion of carbon nanotubes without any agglomerates. It was found that nanotubes modified with amino groups lead to the increase of epoxy matrix crosslinking density. The significant increase in T _g was also observed. On the other hand, addition of carbon nanotubes leads to the decrease of thermal stability of polymer due to the increase of thermal diffusivity.     

Benzidine/Quinoidal-Benzidine-Linked,Superbenzene-Based π-Conjugated Chiral Macrocycles and Cyclophanes

Synthesis of fully conjugated cyclophanes containing large-size polycyclic aromatics is challenging. Now, three benzidine-linked, hexa-peri-hexabenzocoronene (superbenzene)-based ortho-, para-, and meta-cyclophanes are synthesized through intermolecular Yamamoto coupling reaction of structurally pre-organized precursors. Subsequent oxidative dehydrogenation gave the corresponding quinoidal benzidine-linked cyclophanes. Their geometries were confirmed by X-ray crystallographic analysis and their electronic properties were investigated by electronic absorption, cyclic voltammetry, and DFT calculations. The quinoidal benzidine-linked cyclophanes show thermally populated paramagnetic activity with a relatively large singlet-triplet energy gap. Two enantiomers for the ortho-cyclophanes ( 1-NH and 1-N ) were isolated and their chiral figure-of-eight macrocyclic structures were identified. The cage-like cyclophanes 2-NH and 3-NH with concave surface can selectively encapsulate fullerene C₇₀.     

Synthesis and Transformation of 4-(1-Chloro-1-nitroethyl)-6,7-dimethoxy-2-methylquinazoline: Spectral Characterization and Anti-cancer Properties of some Novel Quinazoline Derivatives

An efficient and simple method has been reported for the synthesis of 4-(1-Chloro-1-nitroethyl)-6,7-dimethoxy-2-methylquinazoline ( 2 ) as a key compound for further transformation to other novel 6,7-dimethoxy-2-methyl-4-substituted quinazolines. The structure of the synthesized compounds was characterized by spectroscopic methods. The pathway of some unprecedented reactions was proposed. (E)-1-(6,7-dimethoxy-2-methylquinazolin-4-yl)-3-(4-nitrophenyl)prop-2-en-1-one (11) exhibits high in vitro cytotoxicity on three cell lines, Hepatocellular carcinoma (Hep-G2), Human lung carcinoma (LU-1), and Human breast carcinoma (MCF-7) with IC₅₀ of 2.1, 11.6 and 2.2 μM, respectively.