Are lateral and perceptual asymmetries related to WISC-R and achievement test performance in normal and learning-disabled children?

An analysis of the performance of matched populations of 23 normal and 23 learning-disabled children (9 yrs 2 mo to 13 yrs) on a measure of handedness and perceptual asymmetry (auditory–linguistic) revealed significant differences between groups on these measures. However, no relationship between measures of lateral or perceptual asymmetry and intelligence or math and reading achievement was noted. It is suggested that deviations in lateral or perceptual asymmetry be considered as potentially symptomatic rather than pathogenic. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age- and sex-related differences in left- and right-hemisphere processing by learning disabled children.

Age and sex differences in left- and right-hemisphere processing were assessed with 2 dichotic listening tasks in a sample of 48 control and 48 learning-disabled (LD) children ranging in age from 6 yrs 9 mo to 12 yrs 4 mo. Children were presented with consonant–vowel syllables (CVs) and simple square-wave and complex square-wave tones. Neither age nor sex differences in response accuracy or lateralized processing of CV stimuli were evident for control children. Borderline significance was obtained for tonal stimuli. In contrast, CV stimuli elicited a bilateral response in younger LD children, and tonal stimuli elicited a bilateral response in all LD children. Furthermore, control children were oppositely lateralized for verbal and nonverbal stimuli, whereas LD Ss exhibited a general processing bias to the same hemisphere. These data support the theory that LD children may lack the necessary functional specialization required for lateralized processing of such stimuli. In addition, these data do not fully support the developmental invariance hypothesis and may even suggest a putative right-hemisphere or bilateral processing deficiency in LD children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Binary Cellulose Nanocrystal Blends for Bioinspired Damage Tolerant Photonic Films

Most attempts to emulate the mechanical properties of strong and tough natural composites using helicoidal films of wood‐derived cellulose nanocrystals (w‐CNCs) fall short in mechanical performance due to the limited shear transfer ability between the w‐CNCs. This shortcoming is ascribed to the small w‐CNC‐w‐CNC overlap lengths that lower the shear transfer efficiency. Herein, we present a simple strategy to fabricate superior helicoidal CNC films with mechanical properties that rival those of the best natural materials and are some of the best reported for photonic CNC materials thus far. Assembling the short w‐CNCs with a minority fraction of high aspect ratio CNCs derived from tunicates (t‐CNCs), we report remarkable simultaneous enhancement of all in‐plane mechanical properties and out‐of‐plane flexibility. The important role of t‐CNCs is revealed by coarse grained molecular dynamics simulations where the property enhancement are due to increased interaction lengths and the activation of additional toughening mechanisms. At t‐CNC contents greater than 5% by mass the mixed films also display UV reflecting behaviour. These damage tolerant optically active materials hold great promise for application as protective coatings. More broadly, we expect the strategy of using length‐bidispersity to be adaptable to mechanically enhancing other matrix‐free nanoparticle ensembles.     

The effect of radiofrequency energy on the length and temperature properties of the glenohumeral joint capsule

Two isozymes of mammalian methionine adenosyltransferase, MAT I and MAT III, are expressed solely in adult liver. They are, respectively, tetramers and dimers of a single subunit encoded by the gene MAT1A. A third isozyme, MAT II, contains a catalytic subunit encoded by a separate gene, MAT2A, and is expressed in a variety of tissues, including (to a slight extent) adult liver. Based on a recent finding that 2 children with isolated hypermethioninemia and brain demyelination were homozygous for MAT1A mutations predicted to produce severely truncated proteins, and devoid of activity when expressed, it was concluded that complete lack of MAT I/III activity may be associated with neurological symptoms and demyelination. We now report that a 43-year-old man with persistent isolated hypermethioninemia, previously demonstrated to have deficient MAT activity in his liver, has normal brain myelination on MRI and normal neurological function, despite being homozygous for a 539 TG insertion in exon V of MAT1A, so that the gene is predicted to encode a protein of only 184 rather than the normal 395 amino acids. This patient's exon V mutation was demonstrated by SSCP analysis and verified by sequencing. Both parents are heterozygous for the same insertion. This suggests that MAT1A mutations producing severely truncated proteins do not necessarily produce brain demyelination. This finding has relevance to a previously reported 4-year-old girl who was also homozygous for the 539insTG mutation. Finally, our patient's 7% residual hepatic MAT activity, measured at 1 mM methionine, may reflect the hepatic activity of the more ubiquitous enzyme form, MAT II.     

Effect of directed attention on cerebral asymmetries in normal and learning-disabled children.

Using a dichotic listening task employing both undirected and directed attention conditions, cerebral asymmetries were examined in matched populations of 32 normal and 32 learning-disabled (LD) children (ages 7 yrs 6 mo–13 yrs 2 mo). The analysis of recall performance indicated that development was not a significant factor in either group; both the normal and LD Ss showed a right-ear effect, although the LD Ss performed at a degraded level and were unable to demonstrate a right-ear advantage (REA) when attention was directed to the left ear, unlike normal Ss, who produced the REA despite the directed attention conditions. Results suggest that LD children probably do not suffer from developmental delays but rather from a defect in callosal functioning that interferes with their ability to process verbal information simultaneously. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integrated psychological services in the Greeley-Evans public schools.

Integrated school psychological services were implemented 12 years ago in the Greeley-Evans Public Schools by combining the positions of school psychologist and school social worker and placing each professional in an elementary school full-time. After 5 years, services were expanded to secondary schools such that all schools had a full-time school psychologist. Using Bennett's (1988) model for the evaluation of alternative services to determine success in meeting stated goals, a number of positive outcomes were achieved. A time-use survey indicated increased involvement with a variety of interventions for school psychologists. The results of a consumer satisfaction questionnaire given to teachers, administrators, and support personnel also suggested positive perceptions of the new role. Additionally, placement of students with significant emotional disturbance decreased over this time period relative to a 34% student enrollment increase. It is hoped that the long-term implementation of an alternative school psychological services model such as this one will encourage others to enact ecologically responsive services relative to their unique systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

General analysis of microwave network scattering parameters for characterization of thin film materials

A general solution of the linear passive microwave network is presented for the characterization of thin film materials at high microwave frequencies. The mathematical formulas that correlate scattering parameters S₁₁ and S₂₁ with the distributed circuit parameters of the Z₀;Z_s;Z₀ network are given in closed form. The applicability of the general network model to the characterization of thin film materials is illustrated experimentally for one-port reflectometry in the coaxial configuration and for the two-port transmission reflection method in a coplanar waveguide configuration.     

Flow-induced properties of nanotube-filled polymer materials

Carbon nanotubes (CNTs) are under intense investigation in materials science owing to their potential for modifying the electrical conductivity sigma, shear viscosity eta, and other transport properties of polymeric materials. These particles are hybrids of filler and nanoscale additives because their lengths are macroscopic whereas their cross-sectional dimensions are closer to molecular scales. The combination of extended shape, rigidity and deformability allows CNTs to be mechanically dispersed in polymer matrices in the form of disordered 'jammed' network structures. Our measurements on representative network-forming multiwall nanotube (MWNT) dispersions in polypropylene indicate that these materials exhibit extraordinary flow-induced property changes. Specifically, sigma and eta both decrease strongly with increasing shear rate, and these nanocomposites exhibit impressively large and negative normal stress differences, a rarely reported phenomenon in soft condensed matter. We illustrate the practical implications of these nonlinear transport properties by showing that MWNTs eliminate die swell in our nanocomposites, an effect crucial for their processing.     

Preservation of Surface Conductivity and Dielectric Loss Tangent in Large‐Scale,Encapsulated Epitaxial Graphene Measured by Noncontact Microwave Cavity Perturbations

Regarding the improvement of current quantized Hall resistance (QHR) standards, one promising avenue is the growth of homogeneous monolayer epitaxial graphene (EG). A clean and simple process is used to produce large, precise areas of EG. Properties like the surface conductivity and dielectric loss tangent remain unstable when EG is exposed to air due to doping from molecular adsorption. Experimental results are reported on the extraction of the surface conductivity and dielectric loss tangent from data taken with a noncontact resonance microwave cavity, assembled with an air‐filled, standard R100 rectangular waveguide configuration. By using amorphous boron nitride (a‐BN) as an encapsulation layer, stability of EG's electrical properties under ambient laboratory conditions is greatly improved. Moreover, samples are exposed to a variety of environmental and chemical conditions. Both thicknesses of a‐BN encapsulation are sufficient to preserve surface conductivity and dielectric loss tangent to within 10% of its previously measured value, a result which has essential importance in the mass production of millimeter‐scale graphene devices demonstrating electrical stability.     

High-frequency input impedance characterization of dielectric films for power-ground planes

Broadband impedance characterization of high dielectric constant (high-k) films was performed using a coaxial test fixture configuration. The presented coaxial test fixture and broadband measurement methodology of impedance for high-k films minimizes systematic uncertainties by reducing the interconnection inductance and improving the calibration procedure. In the APC-7 configuration, the technique enables accurate evaluation of impedance at frequencies of 100 MHz to 10 GHz with resolution of 0.01 /spl Omega/. The electrical characteristic of high-k films was found to be consistent with a capacitive load without significant contribution from the circuit inductance that typically dominates the high-frequency response. The experimental data and numerical simulations showed that high-k organic-ceramic composite materials could considerably suppress resonant behavior of the power-ground planes. It was found that high-k organic resins filled with ferroelectric ceramic powders exhibit a high-frequency dielectric loss that increases with increasing volume fraction of the ceramic component. The dielectric dispersion and the corresponding dielectric loss of organic-ceramic hybrid materials can serve as an effective mechanism for suppressing the resonant standing waves in power-ground planes.