Propagation characteristics in an underground shopping area for 5‐GHz‐band wireless access systems

5‐GHz‐band wireless access systems, such as the RLAN (Radio Local Area Network) system of IEEE 802.11a, HiperLAN/2, HiSWANa, and AWA, are deployed for indoor use at transmission rates over 20 Mbps. These 5‐GHz access systems are expected to extend service areas from the office to the so‐called “hot spots” in public areas. Underground shopping malls are one type of service area where the application of such nomadic wireless access service can be expected. In order to design radio zone configurations, it is necessary to know broadband propagation characteristics of an underground mall environment even if results obtained by previous measurements in the narrow band are available. This paper presents results of an experimental study on the propagation characteristics for broadband wireless access systems in an underground mall environment. First, broadband propagation path losses are measured and formulated considering the shadowing by human body. A ray trace simulation is used to clarify the basic propagation mechanism in such a closed environment. Next, it was determined that values of the delay spread at different distances during rush hour periods did not exceed 65 ns, which is lower than the permitted maximum value of the present 5‐GHz systems. The final conclusion is that the above propagation characteristics corroborate results of transmission tests carried out by using the AWA equipment. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(3): 55–64, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20059     

Influence of geological setting of islands and significance of reefs for tsunami wave impact on the Atoll Islands, Maldives

This paper discusses the influence of the geological setting of islands and reefs in the Maldives on the impact of the 26 December 2004 Indian Ocean Tsunami. Geological and geomorphological data (including orientation, location, size, ellipticity, reef-island distance, proportion of reef area to island area) were collected for completely flooded and <25% flooded islands. The results show that although the different parameters may interact to reduce or magnify the impact, the reef-island distance is the most important factor. The critical minimum distance between the reef and the island shoreline required for the wave to set up is estimated as 89 m on the eastern and 140 m on the western sides of the island, respectively. Circular islands with short reef-island distance and small percent of reef area seem to be safer in the context of tsunami. The result of this study can be applied to identify islands that are naturally protected/resilient against natural disasters such as tsunami and those where the hazard is greatest.     

Improvement of moment-based probability table for resonance self-shielding calculation

In the present paper, an improved method has been proposed to produce a probability table needed for the resonance self-shielding calculations with the sub-group method. The proposed method is based on a relation between the effective cross section and the cross section moment, which is obtained from a numerical analysis. Using the proposed method, more accurate probability tables can be obtained with less number of the tabulated steps than the conventional method. This enables us to reduce computation time and computer memory storage for the sub-group calculations.     

Deposition chemistry in the Cat-CVD processes of the SiH4/NH3 system

Laser spectroscopic as well as mass-spectrometric techniques were employed to examine the deposition chemistry in the catalytic chemical vapor deposition processes of the SiH₄/NH₃ system. The absolute densities of NH, NH₂ and SiH₃ radicals were measured under various conditions. The densities of the stable products, H₂ and N₂, as well as those of the reactants, NH₃ and SiH₄, were also measured. The NH₂ density is always higher than that of NH and both densities decrease by the addition of SiH₄. The SiH₃ density increases nonlinearly with the increase in the SiH₄ pressure. The SiH₃ density was found to be much higher than that of NH₂ under near practical deposition conditions to fabricate Si₃N₄ films (an NH₃ to SiH₄ flow-rate ratio of 50:1, a total pressure of 20 Pa and a catalyzer temperature of 2300 K). No aminosilane molecules were identified, suggesting that the contribution of aminosilyl radicals to the film deposition is minor. Thus, NH₂ and SiH₃ must be the major deposition species to form Si₃N₄.     

Interleukin-21 in Viral Infections

Interleukin (IL)-21 is a cytokine that affects the differentiation and function of lymphoid and myeloid cells and regulates both innate and adaptive immune responses. In addition to regulating the immune response to tumor and viral infections, IL-21 also has a profound effect on the development of autoimmune and inflammatory diseases. IL-21 is produced mainly from CD4⁺ T cells—in particular, follicular helper T (Tfh) cells—which have a great influence on the regulation of antibody production. It is also an important cytokine for the activation of CD8⁺ T cells, and its role in recovering the function of CD8⁺ T cells exhausted by chronic microbial infections and cancer has been clarified. Thus, IL-21 plays an extremely important role in viral infections, especially chronic viral infections. In this review, I will introduce the findings to date on how IL-21 is involved in some typical viral infections and the potential of treating viral diseases with IL-21.     

Comparison of flame propagation properties of petroleum coke and coals of different rank

Ignition and flame propagation characteristics of 18 kinds of coal and a petroleum coke were investigated through a laser ignition experiment. Flame stability was strongly influenced by amount of volatile matter and pyrolysis rate. Lean limit of flame propagation was strongly influenced by amount of volatile matter. Flame propagation was observed when pyrolized volatile matter was mixed with surrounding air or oxygen, until the concentration of pyrolized volatile matter reached a constant value. Flame propagation velocity was strongly influenced by pyrolysis rate. As the pyrolysis rate increased, the flame propagation velocity increased. The flame propagation velocity of petroleum coke was higher than that of coal with the same volatile content. The flame propagation of petroleum coke was superior to what was expected based on the volatile content, primarily because the high pyrolysis rate caused a shorter ignition delay than what would be expected given the volatile content. A database for the lean limit of flame propagation was used to develop a flame stability model to estimate lean flammability of a large-scale burner. The model could predict the effect of the coal rank, the particle diameter distribution for lean flammability limit. The estimated lean flammability limit of petroleum coke (volatile content 11.5%) was equal to that of lv bituminous coal with volatile content of about 15%.     

Fe_2O_3－SrO－TeO_2系半导体玻璃电导的研究

用准急压冷法制成Ｆｅ_２Ｏ_３－ＳｒＯ－ＴｅＯ_２系半导体玻璃并对其直流电导率进行了测定。玻璃形成范围为（以摩尔计）；０≤Ｆｅ_２Ｏ_３≤２３％；０≤ＳｒＯ≤１８％；７５％≤ＴｅＯ_２＜１００％。通过Ｓｅｅｂｅｃｋ系数的测定确认Ｆｅ_２Ｏ_３－ＳｒＯ－ＴｅＯ_２系玻璃为ｎ型半导体玻璃。２００℃的直流电导率为３．７２×１０￣（－５）～１．８２×１０￣（－６）Ｓ·ｃｍ￣（－１）。直流电导率随着Ｆｅ_２Ｏ_３含量的增加而增加，１６５℃时的载流子迁移率和浓度分别为１．１２×１０￣（－９）～３．６７×１０￣－７ｃｍ￣２·Ｖ￣（－１）·Ｓ￣（－１）和２．１７×１０￣（２１）～８．３３×１０￣１９ｃｍ￣（－３）．讨论的结果表明Ｆｅ_２Ｏ_３－ＳｒＯ－ＴｅＯ_２系玻璃的电导机理符合小极化子跳越理论。     

Observation of hydrogen absorption/desorption reaction processes in Li–Mg–N–H system by in-situ X-ray diffractmetry

The in-situ XRD measurements on dehydrogenation/rehydrogenation of the Li–Mg–N–H system were performed in this work. The ballmilled mixture of 8LiH and 3Mg(NH₂)₂ as a hydrogenated phase gradually changed into Li₂NH as a dehydrogenated phase during heat-treatment at 200 °C in vacuum for 50 h. Neither Mg-related phases nor other intermediate phases were recognized in the dehydrogenated phase. With respect to the hydrogenation process, the dehydrogenated state gradually returned to the mixed phase of the LiH and Mg(NH₂)₂ without appearance of any intermediate phases during heat treatment at 200 °C under 5 MPa H₂ for 37 h and during slow cooling down to room temperature through 24 h. In the hydrogenation process at 200 °C under 1 MPa H₂, however, the growing up of the LiNH₂ and LiH phase was observed in the XRD profiles before the 3Mg(NH₂)₂ and 8LiH phases were formed as the final hydrogenated state. This indicates that the LiNH₂ and LiH phase essentially appears as an intermediate state in the Li–Mg–N–H system composed of 3Mg(NH₂)₂ and 8LiH.     

Predominant localization of non-specific lipid-transfer protein of the yeast Candida tropicalis in the matrix of peroxisomes

PXP-18 is a 14-kDa major peroxisomal protein of the yeast Candida tropicalis and a homologue of the non-specific lipid-transfer protein (nsLTP) of mammals. Mammalian nsLTP is thought to facilitate the contact of membranes, to stimulate lipid-transfer between them. If PXP-18 functions like nsLTP, it must be present on organelle membranes. Immunoelectron microscopy of C. tropicalis cells indicated that gold particles, which visualized PXP-18, localized exclusively in the matrix of peroxisomes. Subcellular fractionation followed by Western blotting revealed the association of PXP-18 with peroxisomes in C. tropicalis cells. An enzyme-linked immunosorbent assay revealed that almost all the PXP-18 associated with peroxisomes was detectable after the solubilization of the organelle but not before, implying the predominance of PXP-18 inside peroxisomes. This differential assay was applied to the intracellular import of the intact and truncated PXP-18s expressed in Saccharomyces cerevisiae cells. Most of the intact PXP-18 was shown to be imported into the matrix of host-cell peroxisomes, whereas the truncated PXP-18, which lacked the C-terminal tripeptide Pro-Lys-Leu, no longer targeted peroxisomes. These results are consistent with the view that PXP-18 is the matrix protein of peroxisomes and must function in a system other than that of lipid transfer.     

Catalytic decomposition of NH3 on heated Ru and W surfaces

The catalytic decomposition processes of NH₃ on heated W and Ru-coated W wires were examined by employing laser spectroscopic and mass spectrometric techniques. Laser spectroscopic measurements show that more H atoms are produced on uncoated W wires, while the NH-radical densities are higher for Ru-coated wires, at the same wire temperatures. Mass spectrometric measurements show that the decomposition efficiencies are nearly the same in both systems. The main products on heated W wires must be NH₂ and H, while the production of NH should also be important on Ru-coated W wires.