Symptom perception in childhood asthma: The role of anxiety and asthma severity.

This study tested the relationship of anxiety and asthma severity to symptom perception. Eighty-six children diagnosed with mild or moderate asthma had symptom perception and pulmonary function measured throughout methacholine challenge (to induce bronchoconstriction). Higher trait anxiety was associated with heightened symptom perception (controlling for pulmonary function) at baseline. Greater asthma severity was associated with blunted symptom perception (controlling for pulmonary function) at the end of methacholine challenge and with a slower rate of increase in symptom perception across methacholine challenge. These results suggest that anxiety plays a role when children's symptoms are mild, whereas medical variables such as severity play a role in perception of changes in asthma symptomatology as bronchoconstriction worsens. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Calibration method for measurement of linear nanometric distances by scattered total internal reflection

Scattered total internal reflection of visible light is used to measure linear nanometric distance to as small as 10 nm. Specifically, we measure the height of magnetic transducer heads above a rotating glass disk. A breakthrough in the approach to calibration, based on combining the second derivative of the transmittance of the scattered light and parameter fitting, substantially improves the quality of the measurement relative to previous demonstrations of this method. The results agree to 1 nm with an industry-standard three-color interferometer to and including the lowest values measured. The technique in principle remains robust to as low as the zero height. Furthermore the calibration point can be as low as 10 nm, which is especially attractive in practice.     

Study of individual grown-in and indentation-induced dislocations in GaN by defect-selective etching and transmission electron microscopy

Vickers diamond indentation at 370°C has been employed to introduce dislocations into the plate-like (000-1) N-polar GaN single crystals. It has been established that using standard Vickers diamond indenter, well-defined ‘rosettes’ of defects are formed under 1.5–2 N load applied for 10 min. The resolved patterns of dislocation-related etch pits are formed using molten KOH–NaOH eutectic (E) at 200°C for 1.5–2 min. Individual grown-in dislocations are revealed by this E etch in the GaN matrix. Transmission Electron Microscopy confirmed the correlation of etch pits to individual dislocations emerging at the surface. Nano-crystalline material was found in the highly deformed central region of the indentation rosette. The structure of these nano-crystals was analyzed using electron diffraction. Speculative explanation on a phase transition induced by high local pressure is briefly discussed.     

Microstructure of epitaxial layers deposited on silicon by ion assisted deposition

We demonstrate the epitaxial growth of silicon with ion assisted deposition on pyramidally structured porous silicon and investigate the microstructure of the epitaxial layer with transmission electron microscopy. The major defects in the grown pyramid structure are stacking faults on the {1 1 1} facets of the pyramids, whereas the epitaxial layers on the {0 0 1} facets are defect-free. The stacking fault density decreases by about three orders with increasing the deposition temperature from 600 to 850°C, but is constant when the ion energy changes. Depending on growth conditions Si-interstitials are built into the layers, which during electron microscopy form so called rod-like defects.     

Structural Distortion in Antiferromagnetic BaFe2As2 as a Result of Time-Inversion Symmetry

As reported by Q. Huang et al. (Phys. Rev. Lett. 101, 257003, 2008), neutron diffraction studies show an onset of antiferromagnetic order in BaFe₂As₂ associated with a tetragonal-to-orthorhombic distortion. We determine the group Cmca as the space group of antiferromagnetic BaFe₂As₂ and identify a roughly half-filled energy band of BaFe₂As₂ with Bloch functions of special symmetry as magnetic band. As explained by the group-theoretical nonadiabatic Heisenberg model, the electrons in this narrow band may lower their Coulomb correlation energy by producing just the experimentally observed antiferromagnetic state if this state does not violate group-theoretical principles. However, in undistorted BaFe₂As₂ the time-inversion symmetry of the system interferes with the stability of the antiferromagnetic state. Nevertheless, it can be stabilized by a structural distortion of BaFe₂As₂ going beyond the magnetostriction. We derive two possible structural distortions stabilizing the antiferromagnetic state. These distortions are described by their space groups and consist in mere displacements of the Fe atoms.     

The posterior aortic wall echocardiogram. Its relationship to left atrial volume change

The normal posterior aortic wall echocardiogram shows anterior motion during left ventricular systole and predominantly posterior motion in three phases during left ventricular diastole. In six patients undergoing simultaneous left atrial angiograms and posterior aortic wall echocardiograms, there was excellent correlation between the posterior aortic wall motion and the change in the left atrial angiographic area showing the value of the posterior aortic wall echocardiogram in describing the left atrial volume curve. Left atrial and left ventricular pressures were measured with manometer tip catheters and correlated with simultaneous posterior aortic wall and mitral valve echocardiograms in four patients with atrial septal defects. These echocardiographic, angiographic, and hemodynamic correlations, as well as other evidence reported in this paper suggest that a major portion of posterior aortic wall motion is related to left atrial events and describes the left atrial volume curve.