A cross-sectional study of scanning and pupillary responses to various face and nonface stimuli in children with an autism spectrum disorder and typically developing children

The current study sought to test for the presence of a developmental trend for children with autism spectrum disorder (ASD) from the age of 2 years to 13 years of age in their attention to, and processing of, social images. Children with ASD were expected to show dysregulated pupillary responses that would be associated with a reduction of attention to social images over the span of childhood. Pupil size was measured for children with ASD and typically-developing (TD) peers at baseline and in response to both social and nonsocial stimuli. To investigate the effect of stimulus detail on processing, three types of stimuli were presented during an eye-tracking task: photographs, pictures of figures, and drawings. Contrary to previous reports, there was no effect of age or diagnosis on baseline pupil size. Children with ASD, however, did not show phasic pupillary responses to different stimulus types that were observed in TD children. Regardless of age, children with ASD looked at all stimuli for less time than TD children, with nonsocial images receiving the least amounts of fixation. The results suggest that dysregulation of pupil size may be a less systemic marker of ASD than had been previously reported. Furthermore, larger pupillary dilations were correlated with longer looking time toward social photos, as well as higher MA and less social and communication impairment

Structural precursor to the metal-insulator transition in V_2O_3

The temperature dependence of the local structure of V_2O_3 in the vicinity of the metal to insulator transition (MIT) has been investigated using hard X-ray absorption spectroscopy. It is shown that the vanadium pair distance along the hexagonal c-axis changes abruptly at the MIT as expected. However, a continuous increase of the tilt of these pairs sets in already at higher temperatures and reaches its maximum value at the onset of the electronic and magnetic transition. These findings confirm recent theoretical results which claim that electron-lattice coupling is important for the MIT in V_2O_3. Our results suggest that interactions in the basal plane play a decisive role for the MIT and orbital degrees of freedom drive the MIT via changes in hybridization.Comment: 6 pages, 5 figures, 2 table

Patologías víricas en Ulmus laevis en el este de Alemania

Virus-like leaf symptoms and dieback were observed on elm trees in a public park near Potsdam. Infection with Cherry leaf roll virus (CLRV), Elm mottle virus (EMV), Arabis mosaic virus (ArMV) and Tobacco ringspot virus (TRSV), well known viruses to infected elm trees was excluded by bioassays and serological tests. Poty- or carlavirus- like flexible particles of approximately 750 nm in length were isolated repeatedly from diseased elms. The particles were transmissible to diverse Chenopodium species, a herbaceous indicator. The virus was not a member of the Potyviridae family, based on an ELISA and an RT-PCR assay using a potyvirus genus-specific broad-spectrum polyclonal antibody and family-specific primers, respectively. Also no potyvirus-like pinwheel inclusions were found in leaf cells of infected indicator plants in electron microscopic studies. Further molecular characterization of these virus isolates is under way.En olmos situados en un parque cercano a Postdam, se ha observado la presencia de síntomas foliares similares a los producidos por virus. Mediante bioensayos y pruebas serológicas se descartó la presencia de infecciones originados por el virus del enrollamiento de la hoja del cerezo (CLRV), el virus del moteado del olmo (EMV), el virus del mosaico de Arabis (ArMV) y el virus del anillamiento del tabaco (TRSV), todos ellos bien conocidos por afectar a los olmos. Repetidamente se aisló, en olmos enfermos, partículas flexibles de aproximadamente 750 mm de longitud similares a las de Potyvirus y Carlavirus. Las partículas fueron transmisibles a diversas especies de Chenopodium, un indicador herbáceo. Según una prueba ELISA y un ensayo RT-PCR en que se usaron, respectivamente, un anticuerpo policlonal específico de género de Potyvirus de amplio espectro, y cebadores específicos de la familia, el virus no es miembro de la familia Potyviridae. Tampoco se ha encontrado, en estudios mediante microscopía electrónica, inclusiones del tipo potyvirus en las células de las hojas de plantas indicadoras infectadas. En la actualidad se están realizando nuevas caracterizaciones moleculares de estos aislamientos víricos

Finite-temperature hole dynamics in the t-J model: Exact results for high dimensions

We discuss the dynamics of a single hole in the t-J model at finite temperature, in the limit of large spatial dimensions. The problem is shown to yield a simple and physically transparent solution, that exemplifies the continuous thermal evolution of the underlying string picture from the T=0 string-pinned limit through to the paramagnetic phase.Comment: 6 pages, including 2 figure

Energy spectra of primary and secondary cosmic-ray nuclei measured with TRACER

The TRACER cosmic-ray detector, first flown on long-duration balloon (LDB) in 2003 for observations of the major primary cosmic-ray nuclei from oxygen (Z=8) to iron (Z=26), has been upgraded to also measure the energies of the lighter nuclei, including the secondary species boron (Z=5). The instrument was used in another LDB flight in 2006. The properties and performance of the modified detector system are described, and the analysis of the data from the 2006 flight is discussed. The energy spectra of the primary nuclei carbon (Z=6), oxygen, and iron over the range from 1 GeV amu$^{-1}$ to 2 TeV amu$^{-1}$ are reported. The data for oxygen and iron are found to be in good agreement with the results of the previous TRACER flight. The measurement of the energy spectrum of boron also extends into the TeV amu$^{-1}$ region. The relative abundances of the primary nuclei, such as carbon, oxygen, and iron, above $\sim10$ GeV amu$^{-1}$ are independent of energy, while the boron abundance, i.e. the B/C abundance ratio, decreases with energy as expected. However, there is an indication that the previously reported $E^{-0.6}$ dependence of the B/C ratio does not continue to the highest energies.Comment: 16 pages, 18 figures. Accepted for publication in Ap

Spectral Properties and Bandstructure of Correlated Electron Systems

We present $\vec{k}$-dependent one-particle spectra and corresponding effective bandstructures for the $2d$ Hubbard model calculated within the dynamical molecular field theory (DMFT). This method has proven to yield highly nontrivial results for a variety of quantities but the question remains open to what extent it is applicable to relevant physical situations. To address this problem we compare our results for spectral functions to those obtained by QMC simulations. The good agreement supports our notion that the DMFT is indeed a sensible ansatz for correlated models even in to $d=2$.Comment: Paper presented at SCES '95, Sept. 27 - 30 1995, Goa. To be published in Physica B. 10 pages, figures include

Ferromagnetism in the large-U Hubbard model

We study the Hubbard model on a hypercubic lattice with regard to the possibility of itinerant ferromagnetism. The Dynamical Mean Field theory is used to map the lattice model on an effective local problem, which is treated with help of the Non Crossing Approximation. By investigating spin dependent one-particle Green's functions and the magnetic susceptibility, a region with nonvanishing ferromagnetic polarization is found in the limit $U\to\infty$. The $\delta$-T-phase diagram as well as thermodynamic quantities are discussed. The dependence of the Curie temperature on the Coulomb interaction and the competition between ferromagnetism and antiferromagnetism are studied in the large $U$ limit of the Hubbard model.Comment: 4 pages, 5 figures, accepted for publication in Physical Review B, Rapid Communication

Temperature-dependent electronic structure and ferromagnetism in the d=oo Hubbard model studied by a modfied perturbation theory

The infinite-dimensional Hubbard model is studied by means of a modified perturbation theory. The approach reduces to the iterative perturbation theory for weak coupling. It is exact in the atomic limit and correctly reproduces the dispersions and the weights of the Hubbard bands in the strong-coupling regime for arbitrary fillings. Results are presented for the hyper-cubic and an fcc-type lattice. For the latter we find ferromagnetic solutions. The filling-dependent Curie temperature is compared with the results of a recent Quantum Monte Carlo study.Comment: RevTeX, 5 pages, 6 eps figures included, Phys. Rev. B (in press), Ref. 16 correcte

Magnetic Properties of the t-J Model in the Dynamical Mean-Field Theory

We present a theory for the spin correlation function of the t-J model in the framework of the dynamical mean-field theory. Using this mapping between the lattice and a local model we are able to obtain an intuitive expression for the non-local spin susceptibility, with the corresponding local correlation function as input. The latter is calculated by means of local Goldstone diagrams following closely the procedures developed and successfully applied for the (single impurity) Anderson model.We present a systematic study of the magnetic susceptibility and compare our results with those of a Hubbard model at large U. Similarities and differences are pointed out and the magnetic phase diagram of the t-J model is discussed.Comment: 28 pages LaTeX, postscript figures as compressed and uuencoded file included fil