A fundamental study on the preparation of niobium aluminide powders by calciothermic reduction

Fine niobium aluminide powders such as NbAl₃ were produced directly from mixtures of Nb₂O₅ and aluminum powder by calciothermic reduction. Prior to the reduction experiment, phase equilibria between Nb-Al and Ca-Al alloys were studied. Isothermal annealing of the specimens in the Nb-Al-Ca system at 1273 K showed that NbAl₃ is in equilibrium with CaAl₂ and Al-rich Ca-Al liquid alloys and that Nb₃Al and Nb₂Al equilibrate with Ca-Al alloys containing around 9 to 18 and 18 to 36 mol pct Al, respectively. Based on these experimental phase equilibria and on reported thermodynamic data of the Al-Ca system, the activities of Al in Nb-Al alloys were evaluated. This information is necessary in determining suitable compositions and conditions for the coreduction and ultimate production of single-phase niobium aluminide. The procedure for preparation of niobium aluminide powders by calciothermic reduction of Nb₂O₅ consists of three steps: (1) blending of starting materials (Nb₂O₅ + Al); (2) high-temperature reaction with calcium; and (3) acid leaching. After the reduction of Nb₂O₅ with calcium and aluminum to produce niobium aluminide powders, by-products of Ca-Al alloy, CaAl₂, and CaO were formed. These were removed by leaching in aqueous acid solution. The NbAl₃ particles obtained were a few micrometers in size and contained about 0.15 wt pct oxygen.     

High-energy,all-solid-state,ultraviolet laser power-amplifier module design and its output-energy scaling principle

We demonstrate that a coaxially pumped, large-aperture ultraviolet power-amplifier module with solid-state tunable laser medium Ce(3+):LiCaAlF6 has 98-mJ, 290-nm, and 3-ns output pulses with a sufficient extraction efficiency of 25%. The detailed information of design parameters, including the gain-coefficient dependence on pump condition, is successfully accumulated for further energy scaling for a terawatt-class ultraviolet chirped pulse amplification laser system or a high-pulse-energy laser system.     

Trust-Based Facilitator: Handling Word-of-Mouth Trust for Agent-Based E-Commerce

This paper proposes a facilitator which finds capable and trustworthy partners on behalf of client users (agents), which helps agents form and maintain e-partnerships for electronic commerce. Unlike existing capability-based facilitators or matchmakers, the facilitator collects and maintains private word-of-mouth trust information as well as capabilities from each agent and uses the information for personalized trust-based facilitation for each agent, which is performed through the facilitation protocols and trust propagation mechanism. Compared to other existing trust mechanisms, the characteristics of trust which this facilitator handles are personalized-collaborative-subjective-qualitative-private. The facilitator is implemented as a JATLite multi-agent system and a FIPA-OS based multi-agent system, and is evaluated in terms of the complexity and characteristics. The example of usage is shown in the area of construction supply-chain coordination.     

Single-Crystal Growth and Anisotropy of the Tetragonal 1-2-3 Type Superconductor Ca0.5La1.25Ba1.25Cu3Oy

Single crystals of the tetragonal 1-2-3 type cuprate Ca_0.5La_1.25Ba_1.25Cu₃Oy have been grown by the travelling-solvent floating-zone method. The crystal structure has been determined to belong to the tetragonal P4/mmm by the single-crystal x-ray diffraction for several crystals with different oxygen-contents. The superconducting transition temperature T _c has increased up to 75 K by the annealing in 1000 bar of O₂. Temperature dependences of the resistivities _ab , _c and also the angular dependence of _ab in various constant magnetic fields have been measured. The anisotropic parameter has been estimated as 6.2, which is similar to that of YBa₂Cu₃O₇.     

Analysis and comparison of reflex times and electromyograms of cervical muscles under impact loading using surface and fine-wire electroces

Myoelectric signals [electromyograms (EMGs)] can be collected using either surface or fine-wire electrodes. Application of the latter results in higher-frequency contents of EMG. In the field of impact biomechanics, surface electrodes are more often utilized than fine-wire ones. However, the removal of motion artefacts from EMG recorded under transient loads requires application of high-pass filters with relatively high cutoff frequencies, which may eliminate a significant part of the surface EMG power spectra. Therefore, in the current study, both surface and fine-wire electrodes were utilized to record the EMG of cervical muscles under conditions simulating a rear-end car collision at low speed. The results indicated that application of high-pass filtering at 50 Hz can be necessary to remove motion artefacts from the EMG collected under such conditions. Such filtering resulted in a higher decrease in amplitude of the surface EMG than that of the fine-wire one. However, the reflex times obtained here were not significantly affected by the type of the electrodes utilized to collect EMG.     

Stimulatory and inhibitory effects of serotonergic hallucinogens on spinal mono- and polysynaptic reflex pathways in the rat

The effects of two 5-HT-related hallucinogens on rat spinal mono- and polysynaptic reflex pathways in the rat were investigated. 5-Methoxy-N,N-dimethyltryptamine (5-MeODMT, 1 and 100 micrograms/kg, i.v.), an indolealkylamine agent, produced a dose-dependent decrease in the monosynaptic reflex, whereas 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI, 1-100 micrograms/kg), a phenylalkylamine agent, produced a dose-dependent increase in the monosynaptic reflex. Both agents increased the polysynaptic reflex. The 5-HT2 receptor antagonists ketanserin (100 micrograms/kg) and ritanserin (100 micrograms/kg) blocked the effects of DOI on the monosynaptic reflex but only partially blocked the 5-MeODMT-induced effect on the monosynaptic reflex. These antagonists inhibited the change in polysynaptic reflex, induced by DOI but not by 5-MeODMT. Neither propranolol (1 mg/kg) nor 3-tropanyl-3,5-dichlorobenzoate (MDL 72222, 1 mg/kg) antagonized the effect of either agent. 5-Methoxy-N,N-dimethyltryptamine and DOI increased the excitability of motoneurons and this effect was inhibited by ketanserin. These results indicate that the two types of hallucinogens possess both common and distinct characteristics, with regard to their action on the spinal reflex: (1) both increase the activity of motoneurons through 5-HT2 receptors but (2) only 5-MeODMT has an inhibitory action on the pathway of the monosynaptic reflex.     

Dual pathways of tubular morphogenesis of vascular endothelial cells by human glioma cells: vascular endothelial growth factor/basic fibroblast growth factor and interleukin-8

In this study, we examined whether human glioma cells are angiogenic in a model using human microvascular endothelial cells, and also which factor is responsible for the glioma-dependent angiogenesis. Tubular morphogenesis in type I collagen gel by human microvascular endothelial cells was stimulated in the presence of 10 and 100 ng/ml of vascular endothelial growth factor (VEGF), 10 ng/ml basic fibroblast growth factor (bFGF) and 10 ng/ml of interleukin-8 (IL-8). Tube formation of the microvascular endothelial cells was assayed in the glioma cell lines IN157 and IN301, co-cultured using the double chamber method. IN301 cells had much higher levels of VEGF, bFGF and transforming growth factor-beta mRNA than IN157 cells, whereas the two had similar levels of transforming growth factor-alpha mRNA. By contrast, IN157 cells had much higher levels of IL-8 mRNA than IN301 cells. IN301-dependent tubular morphogenesis was inhibited by anti-VEGF or anti-bFGF antibody, and the inhibition was almost complete when anti-VEGF and anti-bFGF antibodies were present. On the other hand, IN157-dependent tubular morphogenesis was inhibited by anti-IL-8 antibody, but not by anti-VEGF or anti-bFGF antibodies. These findings demonstrated dual paracrine controls of tumor angiogenesis by human glioma cells. One is mediated through VEGF and/or bFGF, and the other, through IL-8.     

A novel batch-type hydrogen transmitting system using metal hydrides

In the case of transporting hydrogen by means of metal hydrides, a key problem is to reduce the weight of the portable container filled with metal hydrides. The paper describes a novel batch-type hydrogen transmitting system characterized by a portable light container filled with metal hydrides, which is not pressure-proof but only mechanically durable. Hydriding is performed by setting the portable light container in a fixed pressure-proof vessel and admitting hydrogen and nitrogen inside and outside the portable container, respectively, while adjusting the pressure difference between both gases to be zero. Using this system, 2.9 Nm³ of hydrogen can be stored in 14.3 kg of the total mass of the solid constituents including 3.5 kg of Mg-10% Ni alloy. The portable container contains twice as much hydrogen per unit weight and volume as a conventional compressed gas cylinder. Due to the advanced design of this portable container, the optimum hydrogen content could be around 5 wt % based upon the total mass of the container.     

A Study on Pulse Search Algorithms for Multipulse Excited Speech Coder Realization

This paper describes and compares several kinds of pulse search methods for multipulse excited speech coder realization. These pulse search methods are derived from minimization criterion for errorpower between original speech and synthetic speech, but their performances and required computation amounts are different. Objective and subjective evaluations are carried out to compare the performances. Further, the relation between speech quality and pulse search method complexity is described. Based on these results, pulse search methods suitable for realizing a high-quality multipulse coder using current VLSI technology are discussed.