Anomalous Hall Effect and Magnetoresistance of SrFe1-xCoxO3-d

Transport and magnetic studies on polycrystalline samples of SrFe1-xCoxO3-d have been carried out to investigate the relationship between the magnetic structure and the anomalous Hall resistivity rH. The hysteretic behavior of the magnetization observed in the measurements with varying temperature T up and then down after zero field cooling indicates that the system has the reentrant spin-glass phase, which is supported by the increasing width of the magnetic reflections observed by neutron diffraction with decreasing T below the Curie temperature TC. Detailed analyses of the observed Hall resistivity rH indicate that the anomalous Hall coefficient exhibits unusual behavior in the reentrant spin-glass phase. The magnetic field (H)- and T-dependence of the magnetoresistance of the present system can be understood by a spin dependent tunneling model.Comment: 10 pages, 11 figures, J. Phys. Soc. Jpn. 72 (2003) No.

Elemental fluorine - Part 16. Versatile thin-film gas-liquid multi-channel microreactors for effective scale-out

Versatile and conveniently operated microreactor devices, suitable for long term chemical synthesis for both laboratory and industrial use, are described. Direct fluorination of ethyl acetoacetate by fluorine gas is used as a model reaction to illustrate the successful application of reactors having either 9, 18 or 30 microchannels, with all channels supplied from single reagent sources, to provide significant quantities of fluorinated products. Convenient reactor maintenance, simple design, versatility and the enhanced safety features of using such modular microreactor devices, make these systems appropriate for synthesis on the large scale

beta-amino acids to piperidinones by petasis methylenation and acid-induced cyclization

[GRAPHICS] Ester-imine derivatives of beta-amino acids were methylenated with dimethyltitanocene under microwave irradiation and the resulting enol ethers cyclized with Bronsted acid or triisopropylaluminium to give 2,6-syn-disubstituted piperidinones in good yield and diastereoselectivity. The method is analogous to the Petasis-Ferrier rearrangement of 1,3dioxan-4-ones to give tetrahydropyranones

Enantioselective Synthesis of the C1–C6 and C7–C23 Fragments of the Proposed Structure of Iriomoteolide 1a

[Image: see text] Synthesis of the C1-C6 and C7-C23 fragments of the proposed structure of iriomoteolide 1a has been accomplished. Key steps include a cross metathesis to form the C15-C16 E olefin and a chelation controlled Grignard addition to form the tertiary alcohol at C14. Notably, 7 of the 9 stereocenters of the proposed structure have been set using various aldol reactions employing metallo enolates of thiazolidinethiones