Review on distorted face-centered cubic phase in yttrium via genetic algorithm

We present two distorted face-centered cubic (dfcc) structures of yttrium under high pressure, which have been found by a first-principles genetic algorithm technique. The structures are a tetragonal P4₃ (dfcc-I) and a triclinic P1¯ (dfcc-II), formed by slight distortions from a trigonal R3¯m structure reported as the dfcc phase earlier. The enthalpy difference between the two dfcc structures is less than 0.2 mRy/atom, and dfcc-I is marginally more stable than dfcc-II in lower pressure region. The enthalpy comparison among candidate structures indicates the structural phase transitions into dfcc-I at 41 GPa, into dfcc-II at 81 GPa, and into an orthorhombic Fddd structure at 106 GPa.     

Online tool for calculating null points in various inversion recovery sequences

Accurate equations for calculating the inversion time of the null point (TI_null) in inversion recovery (IR) sequences are required for adequate suppression of fat or cerebrospinal fluid (CSF) but are not widely known. The purpose of this study is to elucidate the process of deriving accurate TI_null equations using schematic diagrams that allow the equations to be easily understood, and to devise a convenient online tool for instant calculation of TI_null.     

Finite element analysis of two- and three-dimensional flows around square columns in tandem arrangement

Two- (2D) and three-dimensional (3D) finite element analyses for flow around two square columns in tandem arrangement were performed with various column spacings and Reynolds numbers. The computed values were compared with the wind-tunnel results in terms of the aerodynamic characteristics of the leeward column. In most 2D computations, strong vortices were formed behind the windward column, irrespective of widely changed Reynolds numbers. This was different from the experimental phenomena of equivalent spacing, so that the computed time-averaged pressure coefficients were not identical to the experimental values except when the distance between the two columns was adequately wide or narrow. On the other hand, in 3D computation, distinct differences in flow structures behind the column were observed between Reynolds numbers of 10³ and 10⁴ and the pressure coefficient in the 3D analysis with Re=10⁴ agreed well with the experimental value. Thus, the effectiveness of 3D computations and Reynolds number effects on the flow around two square columns have been confirmed. © 1998 John Wiley & Sons, Ltd.     

Facile synthesis of furobenzothiazepines

The reaction of methyl 5-(2-isocyanatophenylthio)-2-furancarboxylate 2 with N-methylpiperazine gave 5-(2-N-piperazinocarbamoylphenylthio)-2-furancarboxylate 3a . Furthermore, 4-N-methylpiperazinyl-2-methoxycarbonylfuro[2,3-b][1,5]benzothiazepine 4a was obtained by the Bischler-Napieralski reaction of 3a with phosphorus oxychloride in the present of phosphorus pentoxide. Three furobenzothiazepines could be obtained using the same method. Based on the pharmacological studies of these compounds, it was found that 4-morpholinyl-2-methoxycarbonylfuro[2,3-b][1,5]benzothiazepine 4b had anti-inflammatory activity similar to flufenamic acid.     

Vortical flow in thermo-acoustic devices

Taconis oscillation in a closed long tube with large thermal gradient is studied by numerical calculation of the 2D compressible Navier-Stokes equations. The both ends of tube are hot (T = T_H), and the center of side wall is cold (T = T_C). We analyze the pressure amplitude p_amp and the time averaged temperature T_m in the closed tube. p_amp is almost homogenous in the tube cross section, however, T_m is not homogenous in the central cold region. We also observe two steady states at the same temperature ratio θ = T_H/T_C. It is important to analyze the effects of the boundary layer in this cold region on Taconis oscillations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spin selectivity in the oxygenation of singlet phenylhalocarbenes with oxygen

Singlet phenylhalocarbenes are shown to react with triplet oxygen and the apparent spin-forbidden oxygenation rates are strongly dependent on substituents, i.e. in the decreasing order of Br>Cl?F for halogen and of p-NO₂>H?p-MeO for p-substituents. These results suggest the oxygenation of triplet halocarbene equilibrated with ground-state singlet, resulting in the first estimation of energy difference between the singlet and triplet states.