Correlation of regional cerebral blood flow from perfusion MRI and spect in normal subjects

The objective of this study was to determine the relationship in regional cerebral blood flow (rCBF) as measured with perfusion magnetic resonance imaging (pMRI) and single photon emission computer tomography (SPECT). rCBF was determined in 26 healthy subjects with pMRI and SPECT. After co-registration of pMRI with SPECT, rCBF was determined in 10 brain regions relative to the whole slice value. pMRI was evaluated with and without elimination of large vessels. rCBF from pMRI correlates significantly with rCBF from SPECT (r = 0.69 with and r = 0.59 without elimination of large vessels; p < 0.0001 for both). Elimination of large vessels reduced the interindividual variance of the pMRI measurements in most regions. rCBF from pMRI shows good correlation with rCBF from SPECT. Because pMRI is sensitive to flow in large vessels while SPECT is not, elimination of large vessels in pMRI reduces the interindividual variability of pMRI and improves the-correlation between the two methods. pMRI is a reliable noninvasive method for rCBF measurements.     

Control on the Copper Valence and Properties by Oxygen Content Adjustment in the LaCuO3−ySystem (0≤y≤0.5)

The LaCuO_3−yperovskite is considered as the first member of the 01(n−1)nseries of “layered cuprates.” Highly oxidized, stoichiometric LaCuO₃is stabilized under very high oxygen pressures, and was synthesized in a cubic-anvil-type high-pressure apparatus at 5 GPa and 1400°C using excess amounts of KClO₄as an external oxidizing agent. Upon heating under ambient pressure the rhombohedral high-pressure phase loses oxygen yielding tetragonal, monoclinic, and orthorhombic forms of LaCuO_3−yas intermediate products before the final decomposition into La₂CuO₄and CuO or Cu₂O around 800°C. All three oxygen-deficient LaCuO_3−yphases could be isolated and their stability limits and corresponding oxygen contents conveniently investigated by annealing stoichiometric LaCuO₃in a thermobalance of high sensitivity in order toin situdetect the exact amount of oxygen loss. The nominal copper valence values calculated from the oxygen contents are compared and discussed with XPS data as well as with the results evaluated from magnetic susceptibility measurements.     

Atomic resolution STM observation of the Bi---O surface of yttrium substituted Bi2Sr2CaCu2Oy single crystals

We first examined Bi---O surfaces of Bi₂Sr₂CaCu₂O_y single crystals, whose Ca sites were substituted by Y ions, using an ultra-high vacuum scanning tunneling microscope (UHV-STM). Atomic resolution surface images were obtained for both the unsubstituted superconducting crystals and non-superconducting crystals, whose 60% Ca sites were substituted by Y ions. We found a lot of unperiodic disorder in the surface structure of the Y substituted crystal. The disorder seems to be caused by the random distribution of the Y ions.     

Formation of Ca-doped YBa2Cu4O8 phase in thin films

Ca-doped YBa₂Cu₄O₈ (124) thin films are prepared on (100) SrTiO₃ substrates by annealing the amorphous films deposited using a pulsed laser deposition technique. The X-ray diffraction measurements show that the Ca-doped YBa₂Cu₄O₈ phase is formed by annealing below 800°C at a oxygen pressure of 1 atm. The 124 films have c-axis orientation normal to the substrates. As the Ca content increases, the proportion of the 123 impurity phase in the samples increases. The onset temperature of superconductivity of the Y(Ca)Ba₂Cu₄O₈ films increases from 79 K to 88 K with an increase Ca-substitution for 5 to 10% of Y.