Solid-state diffusion bonding of silicon nitride using titanium foils

This article presents an effective way to control the interfacial reaction during solid-state diffusion bonding of silicon nitride (Si₃N₄) using titanium foils. The interfacial structure and its growth kinetics were analyzed in detail with scanning electron microscopy (SEM), electron-probe microanalysis (EPMA), and X-ray diffraction (XRD). The actual phase sequence of the joint interfaces bonded at temperatures between 1473 and 1673 K is concluded to be Si₃N₄/Ti₅Si₃(N)/α-Ti(N)+Ti₅Si₃(N), which is different from the phase sequence observed at room temperature after bonding. The joints are very weak due to the formation of a brittle Ti₅Si₃(N) layer at the interface. To suppress the growth of the Ti₅Si₃ layer, a nitrogen-solution treatment of titanium foils prior to each bonding experiment is implemented. Although a perfect prevention of the Ti₅Si₃(N) layer formation is not achieved with this treatment, it is shown that the growth of the layer is effectively suppressed enough to improve the joint strength to a level 3 times higher than the case in which pure titanium is employed.     

Suppression of mode-hop-induced optical signal deterioration in an external-cavity-diode laser with a fiber-Bragg grating for uncooled wavelength-division-multiplexing applications

This paper reports on an external-cavity-diode laser (ECDL) employing a fiber Bragg grating, which was newly designed for WDM applications without temperature control. An optical signal waveform generated by the novel ECDL when the longitudinal lasing mode hopped was observed directly for the first time. It is confirmed that optical signal degradation caused by mode hopping can be suppressed effectively.     

Influence of electrode material on pressure‐rise due to arc in a closed chamber

This paper describes the phenomenon of internal pressure‐rise due to arcs ignited between metal rod electrodes in air. First, the internal pressure‐rises in a closed chamber due to arcs were measured at currents within the range of 1 to 12.5 kA. The rod electrodes were made of copper, iron, and aluminum, and were 20 mm in diameter. The measurements showed that the maximum pressure‐rise distinctly differed with each electrode material at the same total arc energy, namely, the maximum pressure‐rise was the highest in the case of the aluminum electrode and was the lowest in the case of the iron electrode. Next, to quantitatively verify this difference, the internal pressure‐rise was estimated, taking into account the energy balance in the closed chamber on each electrode material. It was found that the estimated pressure‐rise approximately agreed with the above experimental results by taking into consideration oxidation reactions of the electrodes, melting and vaporization of the electrodes, and radiation loss of the arcs under certain realistic assumptions. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(4): 9–18, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21071     

Proposal of a simplified method for integrating reduction of effective power of pumped storage into a generation system planning method

Pumped storage hydropower stations are extensively used as peaking and reserve power plants. The current trend in this area is to increase their power output relative to the capacity of reservoirs, which results in a shorter maximum duration of full‐power operation while availability of the energy required for the pumping becomes less evident. This increases the possibility of reducing the effective power of pumped storage units in the case of a tight supply–demand balance in the power system. Although many studies have examined a role of pumped storage in generation systems, few studies have explicitly dealt with the power reduction. This paper proposes a new linear programming model that incorporates the reduction of effective power of pumped storage. The proposed model makes it possible to easily incorporate the power reduction in computations by employing hypothetical daily load curves and dispatching loads to the curves. The model also includes LNG combined cycle power generation plants that are now being intensively implemented. The developed model is applied to a power system model. The sample study reveals that the reduction of effective power considerably varies from season to season and the reduction highly affects the optimal generation mix, that is, the optimal share of pumped storage. © 2001 Scripta Technica, Electr Eng Jpn 134(4): 50–61, 2001     

Prospective method of lightning protection schemes in distribution system

Grounding wires and enclosed ZnO elements have been incorporated generally in 6.6‐kV distribution systems by TEPCO for the reduction of lightning overvoltages. At present, the reliability to lightning surges is tolerably good. However, the facility of grounding wires is not inexpensive and its maintenance is hard due to corrosion and disconnection in some areas. A typical model simulating TEPCO field adopting enclosed ZnO elements has been developed and we have evaluated relative failure risks systematically according to conditions with and without grounding wires against lightning overvoltages. Two kinds of failures discussed in the paper are the flashover of insulation and the overduty of ZnO elements, and two kinds of induced and direct lightning overvoltages are studied in flashover. The greatest problem with no grounding wire is the increase of ZnO elements' duty, but it was demonstrated that a short partial grounding wire around ZnO elements or the selection of heavier ZnO elements provides a solution. The main objectives of this study are to clarify the relative failure risks systematically according to realistic field conditions, the risk of small stroke currents having long duration to ZnO elements' duty, and countermeasures against ZnO elements' overduty. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 1–10, 1999     

Cytokine Networks in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic systemic inflammation causing progressive joint damage that can lead to lifelong disability. The pathogenesis of RA involves a complex network of various cytokines and cells that trigger synovial cell proliferation and cause damage to both cartilage and bone. Involvement of the cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6 is central to the pathogenesis of RA, but recent research has revealed that other cytokines such as IL-7, IL-17, IL-21, IL-23, granulocyte macrophage colony-stimulating factor (GM-CSF), IL-1β, IL-18, IL-33, and IL-2 also play a role. Clarification of RA pathology has led to the development of therapeutic agents such as biological disease-modifying anti-rheumatic drugs (DMARDs) and Janus kinase (JAK) inhibitors, and further details of the immunological background to RA are emerging. This review covers existing knowledge regarding the roles of cytokines, related immune cells and the immune system in RA, manipulation of which may offer the potential for even safer and more effective treatments in the future.     

Practical Continuous‐Flow Controlled/Living Anionic Polymerization

A continuous‐flow reaction system was developed, allowing flow conditions of the entire system to be maintained at a predetermined constant level, which is one of the most significant factors for successful industrial application. Controlled/living anionic polymerization was selected as a model reaction since the characteristics of its polymer products, molecular weights, and molecular weight distributions are highly susceptible to changes in the relative flow rates of a monomer and initiator solutions. In flow microreactors, controlled/living anionic polymerization of styrene in tetrahydrofuran (THF)/hexane initiated by THF‐diluted n‐butyllithium (n‐BuLi) was examined. Poly(styrenes) of larger molecule sizes such as Mn > 15 000 were successfully synthesized. After continuous operation for four hours, ca. 0.5 kg of the polymer was readily produced with narrow molecular weight distribution, demonstrating the applicability of this continuous‐flow system for controlled/living anionic polymerization on considerably large scale with a view to its industrial usage in the future.     

2 Gb/s 15 pJ/b/chip Inductive-Coupling Programmable Bus for NAND Flash Memory Stacking

An inductive-coupling programmable bus for NAND flash memory access in solid state drive (SSD) is presented. Compared to the conventional SSD, this wireless interface using relayed transmission reduces power consumption to 1/2, I/O circuit-layout area to 1/40, and achieves a data rate of 2 Gb/s in 0.18 ?m CMOS process. In addition, since this wireless interface enables one package to contain 64 chips, the number of packages is reduced to 1/8.     

Focus on Extracellular Vesicles: Development of Extracellular Vesicle-Based Therapeutic Systems

Many types of cells release phospholipid membrane vesicles thought to play key roles in cell-cell communication, antigen presentation, and the spread of infectious agents. Extracellular vesicles (EVs) carry various proteins, messenger RNAs (mRNAs), and microRNAs (miRNAs), like a “message in a bottle” to cells in remote locations. The encapsulated molecules are protected from multiple types of degradative enzymes in body fluids, making EVs ideal for delivering drugs. This review presents an overview of the potential roles of EVs as natural drugs and novel drug-delivery systems.     

Evaluation of local deformation behavior accompanying fatigue damage in F82H welded joint specimens by using digital image correlation

By using digital image correlation, the deformation behaviors of local domains of F82H joint specimens welded using tungsten inert gas (TIG) and electron beam (EB) welding were evaluated during tensile and fatigue testing. In the tensile test specimens, the tensile strength decreased in the TIG-welded joints, and ductility decreased in both the EB- and TIG-welded joints. Because axial strain increased in the tempered heat-affected zone (HAZ) and led to the fracture of the TIG-welded joint, the strength was considered to have decreased because of welding. In fatigue testing, the number of cycles to fracture for the welded joint decreased to less than 40–60% of that for the base metal. For both fracture specimens, the largest value of shear strain was observed in the region approximately between the fine-grained HAZ and tempered HAZ; this shear strain ultimately led to fracture. Cavities and macrocracks were observed in the fine-grained HAZ and tempered HAZ in the cross sections of the fracture specimens, and geometrical damage possibly resulted in the reduction of fatigue lifetime.