TDPAC study of mechanically alloyed amorphous andintermetallic Fe-Hf alloys

Time differential perturbed angular correlation spectra of the amorphous Fe₅₇Hf₄₃ alloy prepared by mechanical alloying (MA) andthe intermetallic compounds FeHf₂ were measured. The short-range structures in amorphous Fe₅₇Hf₄₃ andintermetallic compounds of FeHf₂ andFe₂Hf are compared from a microscopic point of view.     

Studies of multilayers of Cu-Hf with a variable-energy positron beam

We report on the results of depth-profiling experiments of multilayers of Cu-Hf using a slow position beam. Experimental data reveal that the Hf layers contain many open-volume type defects and that there might be thin oxidized Hf that reduces theS parameter in the interfaces between Cu-Hf.     

The TDPAC study of quasicrystalline and T-phases

Time differential perturbed angular correlation (TDPAC) spectra of the quasicrystalline phase Al₇₉Mn₂₀Si₁ (800 ppm Hf) and the decagonal phase (T-Phase) Al₈₀Mn₂₀ (800 ppm Hf) were measured using the¹⁸¹Hf probe. It is obtained that the structure around the center in Mackay icosahedra in the decagonal phase seems to be distorted in comparison with that in the quasicrystalline phase.     

Hyperfine interaction of 25Al in α-Al2O3 and its quadrupole moment

A brief review is presented of recent work with the Precision Penning Trap Mass Spectrometer, formerly at MIT, now at Florida State University. This includes atomic mass comparisons using single trapped ions; mass comparisons using two simultaneously trapped ions alternated between large and small cyclotron radii; and measurement of the dipole moment of a molecular ion using the polarizability-induced shift in cyclotron frequency.     

19F Magnetic resonance imaging of perfluorooctanoic acid encapsulated in liposome for biodistribution measurement

The tissue distribution of perfluorooctanoic acid (PFOA), which is known to show unique biological responses, has been visualized in female mice by (19)F magnetic resonance imaging (MRI) incorporated with the recent advances in microimaging technique. The chemical shift selected fast spin-echo method was applied to acquire in vivo (19)F MR images of PFOA. The in vivo T(1) and T(2) relaxation times of PFOA were proven to be extremely short, which were 140 (+/- 20) ms and 6.3 (+/- 2.2) ms, respectively. To acquire the in vivo (19)F MR images of PFOA, it was necessary to optimize the parameters of signal selection and echo train length. The chemical shift selection was effectively performed by using the (19)F NMR signal of CF(3) group of PFOA without the signal overlapping because the chemical shift difference between the CF(3) and neighbor signals reaches to 14 kHz. The most optimal echo train length to obtain (19)F images efficiently was determined so that the maximum echo time (TE) value in the fast spin-echo sequence was comparable to the in vivo T(2) value. By optimizing these parameters, the in vivo (19)F MR image of PFOA was enabled to obtain efficiently in 12 minutes. As a result, the time course of the accumulation of PFOA into the mouse liver was clearly pursued in the (19)F MR images. Thus, it was concluded that the (19)F MRI becomes the effective method toward the future pharmacological and toxicological studies of perfluorocarboxilic acids.     

Copper- or phosphine-catalyzed reaction of alkynes with isocyanides. Regioselective synthesis of substituted pyrroles controlled by the catalyst

The copper-catalyzed reaction of isocyanides (CNCH2EWG1) 1 with electron-deficient alkynes (RC[triple bond]CEWG2) 2 gave the 2,4-di-EWG-substituted pyrroles 3 selectively, whereas the phosphine-catalyzed reaction of 1 with 2 afforded the 2,3-di-EWG-subsituted pyrroles 4. Accordingly, regioselective synthesis of substituted pyrroles has been achieved by merely choosing the catalyst.     

Determination of alpha-tocopherol and alpha-tocopherylquinone in rat tissues and plasma by high-performance liquid chromatography with electrochemical detection

Alpha-tocopherol and alpha-tocopherylquinone in rat tissues and plasma were determined simultaneously by using high-performance liquid chromatography-electrochemical detection (HPLC-ED) with dual electrodes in the series mode. Biological samples were saponified in the presence of a mixture of butylated hydroxytoluene, ascorbic acid, and pyrogallol and then extracted with hexane. The compounds were separated on a C18 column using a mobile phase containing 95% methanol and 0.05 M sodium perchlorate as the supporting electrolyte. After HPLC separation, alpha-tocopherylquinone was first reduced at an upstream electrode at -500 mV Both alpha-tocopherol and the reduction product of alpha-tocopherylquinone were then oxidized downstream at +600 mV. Only the downstream electrode current was monitored for the determination. Linearity of the standard curves was obtained over the range 5-30 pmol for alpha-tocopherol and alpha-tocopherylquinone. Minimum detectable quantities (S/N of 3) were 0.25 pmol for alpha-tocopherol and 0.31 pmol for alpha-tocopherylquinone. The method was applied to analysis of the contents of alpha-tocopherol and alpha-tocopherylquinone in rat tissues and plasma. By hyperoxia, the content of alpha-tocopherol was decreased remarkably in lung, and in contrast, the contents of alpha-tocopherylquinone were increased in all tissues studied with the exception of plasma, though the content of alpha-tocopherylquinone in normal rats is quite small. The technique is particularly useful in the quantitation of the oxidation of alpha-tocopherol in biological samples.     

A locally most powerful invariant test for the equality of means associated with covariate discriminant analysis

In this paper, the authors propose a locally most powerful invariant test for the equality of means in the presence of covariate variables. Also the null and nonnull distributions associated with the above test are developed. This problem arises in covariate discriminant analysis and has been treated by various authors, notably Cochran and Bliss 1948, Ann. Math. Statist.19, 151–176 and Rao 1949, Sankhyã9 343–366; 1966. The test derived here locally dominates in power the tests proposed so far. It is also shown that the Cochran-Bliss test is uniformly most powerful in the class of conditional invariant tests.     

Supramolecular polar thin films built by surfactant liquid crystals: polarization-tunable multilayer self-assemblies with in-plane ferroelectric ordering of ion-based dipoles.

Polar order in the phosphonium liquid crystal thin films, which are composed of two-dimensional ion-pair-based domains separated by the insulating hydrocarbon layers, was probed by second harmonic generation (SHG) analysis. Despite the ordinary amphiphilic self-assemblies containing no pi-electron moieties, the solid-state thin films retaining a smectic layer structure showed clearly an SHG activity, while the disordered films without the layer structure were not active at all for the SHG. It was found that the multilayer structure plays a crucial role for the SHG from the phosphonium thin films and the ionic layers act as an SHG-active site. The most significant characteristic of this system is to possess an ability to control SHG intensity electrically. The efficiency of the SHG process in the thin-film assemblies was enhanced by applying an external electric field parallel to the layer plane. Furthermore, through evaluation of thermal stability of the sample films, it was revealed that the SHG signals were detected only in the solid-state temperature range and the disappearance of the SHG occurs earlier than the solid-to-liquid crystalline phase transition. These results demonstrated that the origin of polar order in the phosphonium thin films is due to in-plane noncentrosymmetric arrangement (ferroelectric ordering) of ion pairs as an electric dipole, that is, dipole symmetry in an ionic layer.