Sensory and nonsensory influences on children's performance of dichotic pitch perception tasks

Dichotic pitch perception reflects the auditory system's use of binaural cues to perceptually separate different sound sources and to determine the spatial location of sounds. Several studies were conducted to identify factors that influence children's dichotic pitch perception thresholds. An initial study of school children revealed an age-related improvement in thresholds for lateralizing dichotic pitch tones. In subsequent studies potential sensory and nonsensory limitations on young children's performance of dichotic pitch lateralization tasks were examined. A training study showed that with sufficient practice, young children lateralize dichotic pitch stimuli as well as adults, indicating an age difference in perceptual learning of the lateralization task. Changing the task requirements so that young children made a judgment about the pitch of dichotic pitch tones, rather than the spatial location of the tones, also resulted in significantly better thresholds. These findings indicate that nonsensory factors limit young children's performance of dichotic pitch tasks.     

C-Terminal properties are important for ring-fused 2-pyridones that interfere with the chaperone function in uropathogenic E. coli

Virulence-associated organelles, termed pili or fimbriae, are assembled via the highly conserved chaperone-usher pathway in a vast number of pathogenic bacteria. Substituted bicyclic 2-pyridones, pilicides, inhibit pilus formation, possibly by interfering with the active site residues Arg8 and Lys112 of chaperones in uropathogenic E. coli. In this article we describe the synthesis and evaluation of nine analogues of a biologically active pilicide. Derivatization was performed with respect to its C-terminal features and the affinities for the chaperone PapD were studied with 1H relaxation-edited NMR spectroscopy. It could be concluded that the carboxylic acid functionality and also its spatial location was important for binding. In all cases, binding was significantly reduced or even abolished when the carboxylic acid was replaced by other substituents. In addition, in vivo results from a hemagglutination assay are presented where the derivatives have been evaluated for their ability to inhibit pilus formation in uropathogenic E. coli.     

Synthesis and asymmetric mono-cyclopalladation of 1,1'-di(alpha-dimethylamino)ethylferrocene

Two-step synthesis of 1,1'-di(alpha-dimethylamino)ethylferrocene is described in details. Cyclopalladation of this diamine involving one or two amino groups is reported and the product of asymmetric mono-cyclopalladation is fully characterized.     

Some non-linear aspects of the electronic stages in time-domain modelling of NDE pulse-echo ultrasonic systems

Electronics interfacing with NDE probes frequently include non-linear switching devices and semiconductor networks, which influence the excitation pulses and detected echo signals. Classical approaches to modelling a pulse-echo process use ideal assumptions for the electronics and do not consider these influences on the echoes, which can be very relevant in HF cases. This paper proposes new ways to consider these non-linear effects in a time-domain simulation process, extending previous approaches by including new elements in the modelling. Specific electrical models covering the pulse-echo process are applied in the evaluation of echo-graphic signals. They include semiconductor devices and other non-ideal elements. From these models, and using SPICE as a simulation tool, strong non-linear effects on pulsed responses, computed for both E/R stages of typical NDE transceivers, are analysed.     

Equation of state and pressure induced amorphization of beta-boron from X-ray measurements up to 100 GPa

The equation of state of boron has been measured up to 100 GPa by single-crystal x-ray diffraction with helium as the pressure transmitting medium. Rhombohedral beta-boron is the stable structure up to 100 GPa under hydrostatic conditions. Nonhydrostatic stress stabilizes a different rhombohedral structure. At about 100 GPa a pressure-induced amorphization is observed. The amorphous phase can be quenched to ambient pressure. An explanation is proposed based on the different stability under pressure between intraicosahedra and intericosahedra bonds.     

n-th roots of a non-negative operator. Conditions for uniqueness

In the present paper we study which restrictions must be imposed on the n-th roots of certain non-negative closed operators A on a Banach space so that these roots are unique.Counterexamples are given to show that the two results on this subject in the previous literature are incorrect.Finally, we obtain an explicit formula relating the canonical root A^1/n to another given non-negative n-th root B, and this allows us to establish the conditions for a given element to yield the same value by both roots. This point of view, which had not been considered up to now, provides simple conditions for global uniqueness that need only to be checked on the subspaces D(A)=_n1D(Aⁿ) and R(A)=_n1R(Aⁿ).     

Flow Injection Spectrophotometric Determination of Ferbam Based on a Photochemical Reaction

A flow-injection configuration for the spectrophotometric determination of ferbam is proposed. The procedure is based on the online decomposition of ferbam and complexation of the released Fe³⁺ with oxalate. The ferrioxalate formed is decomposed upon irradiation with visible light. The Fe²⁺ produced in the photochemical reaction was monitored by measuring the absorbance after complexation with ferrozine (_max=562nm). The method shows a linear range between 1.0 and 30µgmL^–1 (2.5×10^–6–7.2×10^–5molL^–1) with a limit of detection of 0.2µgmL^–1. Repeatibility was 0.53% expressed as relative standard deviation (n=10), and reproducibility, studied on five different days, was ±1.23%. The sampling frequency was about 45samplesh^–1. The applicability of the method was tested in the determination of ferbam in waters and grains.Received December 2, 2002; accepted April 13, 2003 Published online July 16, 2003     

Rhombohedral-cubic transition in Li0.2Na0.3La0.5TiO3 perovskite

High-temperature behavior of the fast ionic conductor Li_0.2Na_0.3La_0.5TiO₃ has been investigated by neutron powder diffraction between 300 and 1073 K. The Rietveld analysis of diffraction patterns showed around 1000 K a change from rhombohedral () to cubic () symmetry. During the heating, the tilting of octahedra along the [111] direction of the cubic perovskite decreased and the rhombic distortion of oxygen square windows that relates contiguous A-sites of the perovskite was eliminated. The influence of the octahedral tilting on Li mobility is finally discussed.     

Molecular treatment of charge transfer cross sections in N5+ collisions with H2

We present cross sections for electron capture in N⁵⁺+H₂ collisions in the energy range 100 eV/amu≤E≤6 keV/amu. We employ a model potential aproximation to treat the interaction of the active electron with the cores, and a recently proposed method, which applies the independent particle model to evaluate the Hamiltonian matrix elements. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001