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Ni0.5Zn0.5Fe2−xCrxO4 (0≤x≤0.5) ferrites were successfully prepared by conventional solid state reaction method to investigate the effect of chromium substitution on the structural, electrical and magnetic properties. X-ray powder diffraction results demonstrate that all the prepared samples are well crystallized single-phase spinel structures without secondary phase. As chromium concentration increases, the lattice parameter and crystallite size gradually decrease. The magnetic measurement indicates that saturation magnetization is substantially suppressed by Cr3+ doping, changing from 73.5 A·m2/kg at x=0 to 46.3 A·m2/kg at x=0.5. While the room-temperature electrical resistivity is more than four orders of magnitude enhanced by Cr3+ substitution, reaching up to 1.1×108 Ω·cm at x=0.5. The dielectric constant monotonously decreases with rising frequency for these ferrites, showing a normal dielectric dispersion behavior. The compositional dependence of dielectric constant is inverse with that of electrical resistivity, which originates from the reduced Fe2+/Fe3+ electric dipole number by doping, indicating inherent correlation between polarization and conduction mechanism in ferrite.

This study investigated the clinical value of diffusion tensor imaging (DTI) in predicting the motor outcome in patients with basal ganglia hemorrhage. This prospective study included 23 patients assessed with DTI to measure the fractional anisotropy (FA) value in affected cortical spinal tract (CST) at three time points: day 0, day 30 and day 90 after onset. The motor function score (MFS) was applied to evaluate motor function and patients were divided into good and poor outcome groups according to the MFS on day 90. The mean FA value on day 0 was significantly lower in the poor outcome group than in the good outcome group (p

The mechanisms of acetylene hydrogenation on palladium clusters (Pdn, n = 2–8) are researched by using the B3PW91/GENECP method of density functional theory. The calculation results indicate that there are two possible pathways for the hydrogenation reaction on Pdn cluster from the reactant acetylene to the product ethane. One of the pathways undergoes through two intermediates, the vinyl (Pdn(H)⋯CH CH2) and ethene (Pdn⋯CH2 CH2) to form the ethane, and the other goes along vinylidene (Pdn(2H)⋯C CH2), ethylidyne Pdn(2H)⋯C CH3) and ethylidene (Pdn(2H)⋯CH CH3) to ethane. Those intermediates in the two pathways can convert into each other which make the reaction profile complicated. The value of n in Pdn cluster can directly affect the reaction pathway: when n ≤ 4, the acetylene hydrogenation reaction will proceed via the pathway of Pdn(2H)⋯CH CH → Pdn(H)⋯CH CH2 → Pdn⋯CH2 CH2 → Pdn(2H)⋯CH2 CH2 to form ethane. However, when n > 4, the reaction choose the following pathway: Pdn(2H)⋯CH CH → Pdn(H)⋯CH CH2 → Pdn⋯CH CH3 → Pdn(2H)⋯CH CH3. In addition, the value of their turnover frequency (TOF) for the ethylene formation catalyzed by Pdn cluster is larger than that for ethane, which indicates that the catalytic cycles in the formation of ethylene is efficient.

Synthesis and thermal decomposition of ammonium aluminum carbonate hydroxide (AACH) have been studied. IR, TG, DTA and XRD results showed that, although AACH aged under different pH might have difference in their composition, the crystal structures are the same. The morphology of AACH and the alumina heated to different temperature were observed in an environment TEM, and no dramatic change has been found during the course. BET results showed the specific surface area of alumina decreased with the increasing heating time and temperature. Size distributions of crystal were measured by using a synchrotron radiation small-angle X-ray scattering (SAXS), the distribution peak shifted to smaller diameter as AACH decomposed to gamma -alumina. then theta -alumina. (C) 2001 Elsevier Science B.V. All rights reserved.