Eun Seok Lee

Study of the nonstoichiometry and physical properties of the SrxDy1−xFeO3−y ferrite system

A series of samples in the Sr/sub x/Dy/sub 1-x/FeO/sub 3-y/ system (x = 0.00, 0.25, 0.50, 0.75, and 1.00) have been produced by heating the reactants to 1200/sup 0/C in air under atmospheric pressure. Mohr salt analysis shows that DyFeO/sub 3/ is a stoichiometric compound and that Fe/sup 4 +/ ions and oxygen deficiency compensate for the cation charge deficiency which is caused by substitution of Sr/sup 2 +/ at Dy/sup 3/..mu.. sites. X-ray powder diffraction assigns the compositions x = 0.00 and 0.25 to the orthorhombic system and the composition x = 0.50, 0.75, and 1.00 to the cubic system. The electrical conductivity sharply increases and the activation energy decreases with the presence of mixed iron valency. The Moessbauer spectra of the samples with x = 0.25 and 0.50 are composed of two sets of lines and a single broad peak for x = 0.75.

Contrast Sensitivity Function of Sound Eye after Occlusion Therapy in the Amblyopic Children

To verify the changes of mesopic and photopic contrast sensitivity function of sound eye whose visual acuity was kept the same after occlusion therapy in the amblyopic children. Fourteen sound eyes of amblyopic children (mean; 7.67 years; S.D., 1.50 years) who kept their visual acuity the same after the occlusion therapy were tested. The children had 6 hours of part-time patch therapy for 3 months prior to this examination. Among 14 amblyopic children, 8 were anisometric and 6 were strabismic amblyopes. Using the visual capacity analyzer which measures the minimal contrast level at from low to high spatial frequencies, the contrast sensitivity of sound eye was measured, under both photopic and mesopic condition, before and after 3 months of occlusion therapy. Comparing the contrast sensitivity of sound eye after the occlusion therapy to that before the occlusion, there was no statistical difference in photopic condition. When it comes to mesopic condition, the contrast sensitivity decreased at the intermediate spatial frequency level (3-13 c.p.d, p=0.028) after the occlusion therapy. The occlusion caused statistically significant decrease in mesopic contrast sensitivity, when the visual acuity was not changed after the occlusion therapy. It may indicate that mesopic contrast sensitivity can be considered as a useful tool for early detection of hidden occlusion amblyopia.

[Comparison for risk estimate of aspiration between the revised dysphagia assessment tool and videofluoroscopy in post-stroke patients].

PURPOSEnThe purpose of this study was to determine the significant factors for risk estimate of aspiration and to evaluate the efficiency of the dysphagia assessment tool.nnnMETHODSnA consecutive series of 210 stroke patients with aspiration symptoms such as cough and dysphagia who had soft or regular diet without tube feeding were examined. The dysphagia assessment tool for aspiration was compared with videofluoroscopy using Classification and Regression Tree (CART) analysis.nnnRESULTSnIn CART analysis, of 34 factors, the significant factors for estimating risk of aspiration were cough during swallowing, oral stasis, facial symmetry, salivary drooling, and cough after swallowing. The risk estimate error of the revised dysphagia assessment tool was 25.2%, equal to that of videofluoroscopy.nnnCONCLUSIONnThe results indicate that the dysphagia assessment tool developed and examined in this study was potentially useful in the clinical field and the primary risk estimating factor was cough during swallowing. Oral stasis, facial symmetry, salivary drooling, cough after swallowing were other significant factors, and based on these results, the dysphagia assessment tool for aspiration was revised and complemented.

A study of the nonstoichiometry and electrical conductivity of gadolinium sesquioxide

Abstract The x values of the nonstoichiometric chemical formula, EuO x , have been measured in the temperature range from room temperature to 1100°C under 2 × 10 −1 atm and 10 −2 atm oxygen pressures, and were found to vary between 1.5171 and 1.5927. The enthalpy of formation for x′ in EuO 1.5000 + x′ , Δ H f was 5.17 kcal/mole and 5.12 kcal/mole under these conditions. The electrical conductivity of EuO x , σ, has been measured in the temperature range from 650 to 1100°C under oxygen pressures of 10 −6 −2 × 10 −1 atm, and were found to vary from about 10 −7 −10 −4 Ω −1 cm −1 , which is within the semiconductor range. The conductivity of the oxide, however, was shown to be anomalous at temperatures lower than 600°C. The activation energy for the conductivity increased from 1.16 to 1.22 eV with oxygen pressure. The oxygen pressure dependency of the conductivity (the 1 n value), calculated from the slopes of plots of log σ vs log P o 2 , increased from 1 5.4 to 1 5.0 with temperature from 700 to 1100°C. The nonstoichiometric conduction mechanism of the oxide is discussed in terms of the x′ values, σ values and thermodynamic data.