Nitridation of Silica Characterized by High-Energy X-Ray Diffraction Technique

The structure of amorphous silicon oxynitride formed under nitridation conditions using ammonia gas, before the onset of silicon nitride crystallization, is determined employing high-energy X-ray diffraction (HEXRD) technique. The derived real-space function suggests that smaller ring structures, especially 3R and 4R (R: ring), which are the dominant rings in crystalline silicon nitride, are not major species in amorphous silicon oxynitride, and form in the latter part of the silicon nitride crystallization.     

An Analyzer for Autonomic Nerve Activities in Acute and Chronic Animals

A real-time analyzer for autonomic nerve activity in acute and chronic animals has been developed. This device, using a finite difference method, can separate individual neural spikes from compound nerve action potentials consisting of base-line drift due to bodily movement, 60 Hz power-line interference, and bioelectrical signals such as electromyogram and electrocardiogram, and with poor signal-to-noise ratio recorded in multifiber preparations or whole nerves. Because there is no phase distortion of neural spikes, the precise time interval between the individual neural spikes can be measured and is converted to analog voltage with a rate meter. This device can perform quantitative analyses of compound nerve action potentials in real time, independent of 60 Hz power-line interference, ECG, and base-line drift.     

An update on thoron exposure in Canada with simultaneous ²²²Rn and ²²⁰Rn measurements in Fredericton and Halifax

Naturally occurring isotopes of radon in indoor air are identified as the second leading cause of lung cancer after tobacco smoking. Radon-222 (radon gas) and radon-220 (thoron gas) are the most common isotopes of radon. While extensive radon surveys have been conducted, indoor thoron data are very limited. To better assess thoron exposure in Canada, radon/thoron discriminating detectors were deployed in 45 homes in Fredericton and 65 homes in Halifax for a period of 3 months. In this study, radon concentrations ranged from 16 to 1374 Bq m(-3) with a geometric mean (GM) of 82 Bq m(-3) and a geometric standard deviation (GSD) of 2.56 in Fredericton, and from 4 to 2341 Bq m(-3) with a GM of 107 Bq m(-3) and a GSD of 3.67 in Halifax. It is estimated that 18 % of Fredericton homes and 32 % of Halifax homes could have radon concentrations above the Canadian indoor radon guideline of 200 Bq m(-3). This conclusion is significantly higher than the previous estimates made 30 y ago with short-term radon measurements. Thoron concentrations were below the detection limit in 62 % of homes in both cities. Among the homes with detectable thoron concentrations, the values varied from 12 to 1977 Bq m(-3) in Fredericton and from 6 to 206 Bq m(-3) in Halifax. The GM and GSD were 86 Bq m(-3) and 3.19 for Fredericton, and 35 Bq m(-3) and 2.35 for Halifax, respectively. On the basis of these results, together with previous measurements in Ottawa, Winnipeg and the Mont-Laurier region of Quebec, it is estimated that thoron contributes ～8 % of the radiation dose due to indoor radon exposure in Canada.     

Preparation of spray-dried microparticles using Gelucire 44/14 and porous calcium silicate or spherical microcrystalline cellulose to enhance transport of water-insoluble pranlukast hemihydrate across Caco-2 monolayers

The aim of this work was to prepare spray-dried microparticles using Gelucire®44/14 (GLC) and porous calcium silicate (FLR) or spherical crystalline cellulose (M06) to enhance transport of poorly water-soluble pranlukast hemihydrate (PLH) across Caco-2 monolayers. FLR or M06 were added to the PLH–GLC aqueous mixture prepared by adding distilled water at 60 °C to a melted mixture of PLH/GLC (1/1) at a PLH–GLC/carrier ratio of 1/1 or 1/17. Spray-dried FLR microparticles have the PLH–GLC solid dispersion (SD) in their pores and spray-dried M06 microparticles have the PLH–GLC SD on their surface. The dissolutions of PLH from the spray-dried FLR (SD/FLR = 1/1), spray-dried M06 (SD/M06 = 1/1), and spray-dried M06 (SD/M06 = 1/17) microparticles in Tween 80 aqueous solution were markedly fast. The transport of PLH from the spray-dried FLR (SD/FLR = 1/1) across Caco-2 monolayers was hardly observed. The transport of PLH across Caco-2 monolayers from the spray-dried M06 (SD/M06 = 1/17) increased with time, and the transport was significantly higher compared to that from PLH powder. The addition of polyethylene glycol 1500 into GLC of the spray-dried M06 was effective to increase the transport of PLH across Caco-2 monolayers. Spray-dried microparticles of PLH using GLC and M06 are a feasible means of enhancing transport across Caco-2 monolayers.     

Degradation of methyl orange using short-wavelength UV irradiation with oxygen microbubbles

A novel wastewater treatment technique using 8 W low-pressure mercury lamps in the presence of uniform-sized microbubbles (diameter = 5.79 microm) was investigated for the decomposition of methyl orange as a model compound in aqueous solution. Photodegradation experiments were conducted with a BLB black light blue lamp (365 nm), a UV-C germicidal lamp (254 nm) and an ozone lamp (185 nm+254 nm) both with and without oxygen microbubbles. The results show that the oxygen microbubbles accelerated the decolorization rate of methyl orange under 185+254 nm irradiation. In contrast, the microbubbles under 365 and 254 nm irradiation were unaffected on the decolorization of methyl orange. It was found that the pseudo-zero order decolorization reaction constant in microbubble system is 2.1 times higher than that in conventional large bubble system. Total organic carbon (TOC) reduction rate of methyl orange was greatly enhanced by oxygen microbubble under 185+254 nm irradiation, however, TOC reduction rate by nitrogen microbubble was much slower than that with 185+254 nm irradiation only. Possible reaction mechanisms for the decolorization and mineralization of methyl orange both with oxygen and nitrogen mirobubbles were proposed in this study.     

Refraction and diffraction by a metal-dielectric multilayered structure

An optical refraction prism consisting of metal and dielectric, subwavelength, periodic multilayered thin films has been proposed. The multilayered structure of metal and dielectric thin films has a cylindrical dispersion surface for TM polarized light. The light behaviors are very different from those of conventional glass prisms and photonic crystal superprisms. Refraction and diffraction of the light wave for the metal-dielectric multilayered prism has been investigated by numerical simulations and graphical representation based on the dispersion surface. A prism with 0.2 microm period had an angular dispersion of 0.20 degrees /nm for approximately 0.8 microm wavelength light. The finite thick metal-dielectric multilayered structure acted as a slab waveguide.     

Attractive performance of a Gifford–McMahon cryocooler by co-axial layout of regenerator materials

A novel filling method of regenerator materials, which we name a co-axial layout, is experimentally investigated. The 2nd stage regenerator of a Gifford–McMahon cryocooler was packed with 50% by volume of the co-axial layout (low temperature side) that consisted of 20% Gd₂O₂S and 30% HoCu₂ spheres. The warm temperature side was packed with 50% lead spheres as a single layer. The experimental results show that the cooling power of co-axial layout is almost the same as that of a three-layer layout, 20% Gd₂O₂S, 30% HoCu₂ and 50% lead, at temperatures between the ultimate low temperature (3.0 K) and 6 K. Moreover, at the temperatures above 10 K, the co-axial layout has 1.7–2.0 times the cooling power of the three-layer layout. Thus the co-axial layout produces a major improvement in cooling power. In this paper, the performance of five types of material assortments is discussed.     

Micromechanism of a deformation process before crazing in a polymer during tensile testing

Polymers are popularly used for housing and parts of machines and equipment. However, their mechanical properties, especially the deformation process, have not been clarified. During tensile testing, crazes are thought to be a source of microcracking and fracture, but the relation between the craze formation process and the deformation process before crazing is not understood. In the present work, scanning acoustic microscopy and X-ray diffraction were used to investigate the micromechanism before craze formation in polymethylmethacrylate (PMMA) and polycarbonate (PC). The velocity change of the surface acoustic wave and X-ray diffraction intensity indicated that molecular orientation occurred in a very small area from early stages of plastic deformation. From the results it was thought that texture was heterogeneous and anisotropic in a very small area, the shape of the area was spheroidal with a longer radius in the direction perpendicular to the applied stress, and the molecular chain in the area was oriented parallel to the stress axis. The area is thought to increase with increasing plastic strain.     

Temporal distribution of motorcyclist injuries and risk of fatalities in relation to age, helmet use, and riding while intoxicated in Khon Kaen, Thailand

This study investigated the temporal distribution of risky behaviors among injured motorcyclists, that is, riding unhelmeted or while intoxicated, and showed how they are associated with risk of fatal injuries. Data of motorcyclists injured in Khon Kaen municipality in northeastern Thailand and transferred to Khon Kaen Regional Hospital were obtained from the trauma registry system of the hospital. Case fatalities were compared by time of day, age group, helmet use, and alcohol intoxication. Unhelmeted riding peaked late in the evening and riding while intoxicated peaked around midnight. Both were associated with increased fatality risk after stratification by time of day; the odds ratios were 3.49 (95% confidence interval (CI) = 1.48-9.36) and 3.01 (CI = 1.71-5.19), respectively. Nighttime injuries were not significantly associated with increased fatality risk after stratification by helmet use or alcohol intoxication. Unhelmeted driving was prevalent and associated with higher fatality risk among younger drivers, whereas intoxicated driving was less prevalent among teens but associated with increased risk among those aged 20-39 years. This study shows that riding unhelmeted or while intoxicated can explain the increased fatality risk at night, suggesting that safety education or enforcements should be targeted at specific age groups and appropriate times.     

使用散射X射线的理论强度进行土壤、岩石中的微量重元素的X射线荧光分析

是依据FP法进行土壤、岩石中的Pb ,As等微量重元素的X射线荧光定量分析的方法。FP法对定量元素的荧光X射线进行理论强度计算 ,同时对散射X射线也进行计算 ,用于多种样品的定量分析 ,提高了定量元素准确度。