Interpretation of Si-L2,3 Edge Electron Energy Loss Near Edge Structures (ELNES) from Intergranular Glassy Film of Si3N4 Ceramics

First-principles molecular orbital calculations of model clusters for Si₃N₄, Si₂N₂O, SiO₂ crystals are made by the discrete variational (DV)-Xalpha method in order to interpret features that appear in the Si- L _2,3 edge ELNES spectra. They are understood in terms of interaction among molecular orbitals for their structural units, i.e., [SiX₄] ^n- tetrahedra (X = N, O). Two parameters, i.e., the N/(N + O) ratio, M _N, and the number of N atoms included in a unit tetrahedron, X _N, are found to determine the spectral features. On the basis of this knowledge, spatially resolved ELNES from intergranular glassy films of high-purity Si₃N₄-SiO₂ ceramics is interpreted. The shift in the first peak by 0.9 eV can be ascribed to M _N= 0.43 ± 0.06 in the intergranular film. The N content satisfactorily agrees with that determined by line-profiling of ELNES. Broadening of the first peak can also be explained consistently by considering this amount of N in the glassy film. An example model-cluster of the glassy film, [Si₇N₁₃O₇]^25- is found sufficient to reproduce the ELNES from the glassy film without inclusion of further complexity or inhomogeneity. The presence of N in the intergranular film is proposed to be the result of the topological requirement imposed by the absence of a broken bond. A model structure that may be useful for further structural optimization is given.     

Stabilization of liposomal membranes by carotenoids: Zeaxanthin,zeaxanthin glucoside and thermozeaxanthin

We investigated the membrane-stabilizing effect of three synthesized polar carotenoids, thermozeaxanthin (TZ), zeaxanthin glucoside (ZG) and zeaxanthin (Z), using the fluorescent calcein-leakage measurement from the calcein-entrapped liposomes composed of dipalmitoylphosphatidylcholine (DPPC). The addition of TZ stabilized the liposomal membranes composed of DPPC at pH values ranging from 4.0 to 10.0. The addition of three carotenoids, TZ, ZG and Z, stabilized the membrane at acidic and neutral pH values ranging from 4.0 to 7.5. The values of leakage were lower at 30 °C and highest at 40 °C, and subsequently, gradually decreased at the higher temperature. The addition of TZ and Z stabilized the membranes, whereas, ZG destabilized the membranes at a temperature higher than 50 °C. In addition, the membrane-stabilizing effect of the carotenoids with the calcein-entrapped liposomes composed of lipids extracted from Thermus thermophilus were investigated. The addition of TZ resulted in stabilization of the membrane at all ranges of pH values. However, the addition of Z and ZG destabilized the membrane.     

Oscillation behavior of a high-temperature silicon droplet by the electromagnetic levitation technique superimposed with a static magnetic field

When a static magnetic field was applied to a Si droplet levitated by an electromagnetic force, only one peak was observed to remain in the frequency spectrum. It was the objective of this work to clarify whether this peak can be assigned to the m = ± 2 oscillation or to the rotation of the droplet. By analyzing the behavior of the deflection angle of the droplet in a top view, we conclude that this peak is not due to the surface oscillation of the droplet but to the droplet rotation.     

Determination of elastic moduli for a spherical specimen by resonant ultrasound spectroscopy

Resonant ultrasound spectroscopy (RUS) is based on the principle that mechanical resonant response of solids depends on its elastic moduli, shape and density. Elastic moduli or the other properties can be identified from resonant frequencies as inverse problem. In this study, the method to determine elastic moduli of a spherical specimen without information of resonant mode was described. We confirmed that resonant frequencies have to be measured under condition of free surface, and adequate number of resonant frequencies used in calculation needs enough number to include the sensitive mode to Poisson's ratio. By this method, we determined elastic moduli of BK-7 glass. The calculated frequencies from the elastic moduli determined by this technique had good agreement with the measured, the absolute accuracies for the Δf was less than 0.4%.     

Time–temperature dependency of mode II fracture toughness for bisphenol A type epoxy resin

We investigated the mode II fracture toughness (K_IIc) with time and temperature dependence of the bisphenol A type of epoxy resin. We performed an asymmetric four‐point bending test under various conditions of temperature and displacement rate. We found that K_IIc strongly depended on the displacement rate and the temperature, even at room temperature. Moreover, it was governed by the time–temperature equivalence principle in regard to the fracture time. The time–temperature dependency of K_IIc was similar to that of the loss modulus (E″), and the transition of brittle to ductile fractures occurred nearly simultaneously when E″ peaked. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 51–55, 2005     

Interference suppression factor in DS-CDMA systems

In a wireless DS-CDMA system, the interference power is suppressed by a factor greater than the spreading factor of the spreading code. An investigation into the interference suppression factor is presented and its simple frequency domain expressions for other-user interference from the same system and other systems are derived. Some numerical results are presented for two spectrally overlapped systems with different raised cosine Nyquist filters     

PZT-Polymer 1-3 Composite for High Resolution Ultrasonic Imaging

A novel process has been developed to construct PZT-polymer 1-3 micro composites for high-resolution ultrasonic imaging for medical diagnosis. The key technology is the lost silicon (Si) mold process, by which PZT micro-rod arrays have been successfully fabricated with the finest rod size being 7 μm, the highest aspect ratio exceeding 15. Such fine-scale high-aspect-ratio PZT structures, which are essential for realizing high imaging performance, have never been realized by any conventional technique.     

Protection of Lactobacillus acidophilus from the low pH of a model gastric juice by incorporation in a W/O/W emulsion

The protective effect of a W/O/W emulsion for Lactobacillus acidophilus from a model gastric juice was investigated in order to develop a method for utilizing the advantages of the probiotics. The bacteria were included in the inner-phase solution of the W/O/W emulsion, and a method for counting the viable-bacteria included in the W/O/W emulsion was developed. The relative viability of the bacteria included in the W/O/W emulsion was 49% at 2 h in the model gastric juice, whereas the viability of the bacteria directly dispersed in the juice declined to 1.3% even at 0.67 h. The relative viabilities of the encapsulated bacteria in the model gastric juice at 2 h were 0.12 and 1.10 for the emulsions having the median diameters of 11.9 and 25.4 μm, prepared with inner-phase volume ratios at 0.03 and 0.45, respectively. The relative viabilities of the bacteria in the W/O/W emulsions with the median diameters of 11 and 27 μm, prepared at the homogenization speed of 2.2×10⁴ and 9.8×10³ rpm, were 0.4 and 0.8, respectively. These results suggested that both the inner-phase volume ratio and the median diameter of oil droplet affected the relative viability of the included bacteria.