Metal-Insulator Transition Accompanied with a Charge Ordering in the One-dimensional t-J' Model

We study the metal-insulator transition accompanied with a charge ordering in the one-dimensional (1D) t-J' model at quarter filling by the density matrix renormalization group method. In this model the nearest-neighbor hopping energy t competes with the next-nearest-neighbor exchange energy J'. We have found that a metal-insulator transition occurs at a finite value of t/J'; (t/J')_C = 0.18 and the transition is of first order. In the insulating phase for small t/J', there is an alternating charge ordering and the system behaves as a 1D quantum Heisenberg antiferromagnet. The metallic side belongs to the universality class of the Tomonaga-Luttinger liquids. The quantum phase transition is an example of melting of the 1D quantum Heisenberg antiferromagnet.Comment: 4 pages, 6 Postscript figures, REVTeX, submitted to Phys. Rev.

Origin of the Charge-Orbital Stripe Structure in La_(1-x)Ca_(x)MnO_(3) (x=1/2, 2/3)

We propose the origin of the charge-ordered stripe structure with the orbital ordering observed experimentally in La_(1-x)Ca_(x)MnO_(3) (x=1/2, 2/3), in which the long-range Coulomb interaction plays an essential role. We study a Hubbard model with doubly-degenerate e_g orbitals, and treat the on-site Coulomb interaction (U) and the nearest-neighbor one (V) with the Hartree-Fock approximation. Both the charge and orbital ordering structures observed in experiments are reproduced in a wide region of the U-V phase diagram determined by the present study. The stability of the orbital ordering is also confirmed by the perturbation theory.Comment: 4 pages, 5 Postscript figures, REVTeX, submitted to Phys. Rev. Let

Funding of an enterprise through the issue of bonds

<div><p>Autism spectrum disorder (ASD) has been postulated to involve impaired neuronal cooperation in large-scale neural networks, including cortico-cortical interhemispheric circuitry. In the context of ASD, alterations in both peripheral and central auditory processes have also attracted a great deal of interest because these changes appear to represent pathophysiological processes; therefore, many prior studies have focused on atypical auditory responses in ASD. The auditory evoked field (AEF), recorded by magnetoencephalography, and the synchronization of these processes between right and left hemispheres was recently suggested to reflect various cognitive abilities in children. However, to date, no previous study has focused on AEF synchronization in ASD subjects. To assess global coordination across spatially distributed brain regions, the analysis of Omega complexity from multichannel neurophysiological data was proposed. Using Omega complexity analysis, we investigated the global coordination of AEFs in 3–8-year-old typically developing (TD) children (n = 50) and children with ASD (n = 50) in 50-ms time-windows. Children with ASD displayed significantly higher Omega complexities compared with TD children in the time-window of 0–50 ms, suggesting lower whole brain synchronization in the early stage of the P1m component. When we analyzed the left and right hemispheres separately, no significant differences in any time-windows were observed. These results suggest lower right-left hemispheric synchronization in children with ASD compared with TD children. Our study provides new evidence of aberrant neural synchronization in young children with ASD by investigating auditory evoked neural responses to the human voice.</p></div

Omega complexity of AEFs for the whole head in TD and ASD children.

<p>(A) Omega complexities were calculated by 151 sensors (whole head) in TD and ASD children for each time-window of 50 milliseconds. (B) Log-10 transformed Omega complexities are compared between TD and ASD children with unpaired, two-tailed <i>t</i>-tests for each time window. Children with ASD exhibited significantly higher Omega complexities compared with TD children in the time-window of 0–50 ms (t = 3.90, <i>P</i> = 0.0002). (C) The time-window of 0–50 ms included the early stage of the P1m component. AEF, auditory evoked field. TD, typically developing. ASD, autism spectrum disorder. The error bars represent 1 standard deviation.</p

Omega complexity of AEFs for the left and right hemispheres in TD and ASD children.

<p>Omega complexities were calculated in 40 sensors corresponding to the left (A) and right (C) hemisphere. The Omega complexities of TD children and children with ASD were compared with unpaired two-tailed <i>t</i>-tests for 16 time windows in the left (B) and right (D) hemisphere. No significant differences were observed in any time-windows. AEF, auditory evoked field. TD, typically developing. ASD, autism spectrum disorder. The error bars represent 1 standard deviation.</p