Resistivity, Hall coefficient, magnetoresistance, and microtexture of cellulose carbon films

Dense carbon films of about 20 μm in thickness were prepared from a commercially available cellulose film of 40 μm thick by heat treatment up to 900°C. Carbon films thus obtained were heat treated at temperatures between 1800 and 3000°C for 30–60 min. The heat-treated carbon films were investigated by the measurements of resistivity, Hall coefficient and magnetoresistance at liquid nitrogen temperature. Reflected and transmitted X-ray diffraction experiments and observations by a high-resolution scanning electron microscope (SEM) were also carried out. The results of the resistivity and Hall coefficient for high-temperature-treated specimens indicated that the carbonized film was more graphitizable than bulk glass-like carbons. The magnetoresistance and X-ray diffraction profiles for the high-temperature-treated specimens suggested that each of these specimens substantially consisted of the matrix of granular microtexture and the graphite layer skin. The skin was clearly observed by SEM for the specimens heat-treated at 2800 and 3000°C and their thickness was 100–300 nm.     

Effect of molding pressure on fabrication of low-crystalline calcite block

We have reported that low-crystalline porous calcite block, which is useful as a bone substitute or a source material to prepare apatite-type bone fillers could be fabricated by exposing calcium hydroxide compact to carbon dioxide gas saturated with water vapor. In the present study, we investigated the effect of molding pressure on the transformation of calcium hydroxide into calcite and the mechanical strength of the carbonated compact. Transformation into calcite was almost completed within 72 h, however, a small amount of Ca(OH)₂ still remained unreacted at higher molding pressure because of incomplete penetration of CO₂ gas into the interparticle space due to dense packing of Ca(OH)₂ particles. On the other hand, high molding pressure resulted in an increase in diametral tensile strength (DTS) of the calcite compact formed. Critical porosity of the calcite block was calculated as approximately 68%.     

Fluorescent imaging of endothelial glycocalyx layer with wheat germ agglutinin using intravital microscopy

Endothelial glycocalyx (GCX) is located on the apical surface of vascular endothelial cells and is composed of a negatively‐charged network of proteoglycans and glycoproteins. The GCX plays an important role in maintaining the integrity of vascular walls and preventing leakage of plasma. Therefore, degradation of the GCX is believed to lead to pathological leakage of plasma. Because the GCX is a very thin layer, its ultrastructural image has been demonstrated on electron microscope. To explore the function of the GCX, it should be visualized by a microscope in vivo. Thus, we developed in vivo visualization technique of the GCX under fluorescence microscopy using a mouse dorsal skinfold chamber (DSC) model. To label and visualize the GCX, we used fluorescein isothiocyanate (FITC)‐labeled lectin, which has a high specificity for sugar moieties. We examined the affinity of the different lectins to epivascular regions under an intravital fluorescent microscope. Among seven different lectins we examined, FITC labeled Triticum vulgaris (wheat germ) agglutinin (WGA) delineated the GCX most clearly. Binding of WGA to the GCX was inhibited by chitin hydrolysate, which contained WGA‐binding polysaccharide chains. Furthermore, the septic condition attenuated this structure, suggesting structural degradation of endothelial GCX layer. In conclusion, FITC‐labeled WGA lectin enabled visualization of endothelial GCX under in vivo fluorescence microscopy. Microsc. Res. Tech. 79:31–37, 2016. © 2015 Wiley Periodicals, Inc.     

Development of a chirped pulse amplification laser with zigzag slab Nd:glass amplifiers dedicated to x-ray laser research

A chirped pulse amplification laser with zigzag slab Nd:glass amplifiers dedicated to x-ray laser research is described. The laser provides a 1.6 ps duration pulse with approximately 7 J energy at a repetition rate of 0.1 Hz. In the power amplifier system, laser light is amplified in a two-step manner: The first step is image-relayed multipass amplification up to approximately 1 J with a 10 mm x 10 mm beam. The second step is double-pass amplification up to >10 J with a 10 mm x 90 mm beam. By using this laser system, the saturated amplification of the Ni-like Ag laser at a wavelength of 13.9 nm has been successfully demonstrated.     

Carbon nanotube growth from semiconductor nanoparticles

Nanoscale metal catalysts have been indispensable for carbon nanotube (CNT) synthesis by chemical vapor deposition (CVD). We show that even semiconductor nanoparicles of SiC, Ge, and Si produce single-walled and double-walled CNTs in CVD with ethanol. This implies that nanosize structures might act as a template for the formation of CNT caps composed of five- and six-membered rings. Providing a template for cap formation is the essential role of the catalysts.     

Fine Patterning and Characterization of Gel Films Derived from Methyltriethoxysilane and Tetraethoxysilane

Pregrooves of 1.6 µm pitch for optical data storage have been embossed successfully by pressing a stamper against x CH₃Si(OC₂H₅)₃(100 - x )Si(OC₂H₅)₄-derived gel films (60 ≤ x ≤ 100 mol%) on glass-disk substrates of 130 mm diameter. When x is <40 mol%, the resultant films are too hard to emboss patterns uniformly. The shrinkage of the patterns is ∼4% for all the films when 60 lessthan equal to x lessthan equal to 100 mol%, even after heat treatment at 350°C, so that the nearly net negative shape of the stamper is preserved. The methyl groups in the films decompose at temperatures from 500° to 600°C.     

Electronic structures of hydrogen storage compound, TiFe

The electronic structures of TiFe hydrogen storage compound containing a variety of alloying elements, M, are investigated by the DV-X cluster method in order to understand alloying effects on the hydrogen absorption and desorption characteristics of this compound. It is found that hydrogen atoms make a strong chemical bond with Fe atoms rather than Ti atoms in pure TiFe, despite the larger affinity of Ti atoms for hydrogen than Fe atoms in the binary metal–hydrogen system. It is also shown that the nature of the chemical bond between the constituent atoms determines the stability of TiFe hydrides. For example, the ratio of the Fe(M)–Ti bond order to the Ti–Ti bond order correlates well with the experimental data of the equilibrium plateau pressure of hydrogen.     

Effects of diffuser shape and back pressure on the performance of disk MHD generators

The effects of diffuser shape and back pressure on the performance of closed‐cycle disk MHD generators are investigated with two‐dimensional numerical simulations taking account of the boundary layer. The enthalpy extraction ratio decreases and fluctuates periodically with increase in the back pressure. The amplitude of power output fluctuation and the period depend on the volume of the inverse flow region. For the reduced height diffuser, the inverse flow region is suppressed and the fluctuation becomes smaller than that for the constant height diffuser. When operated with a back pressure lower than an optimum value, the diffuser does not work because of reacceleration in the diffuser. For the higher back pressure, on the contrary, the inverse flow region propagates into the MHD channel, then the enthalpy extraction ratio is reduced and the Mach number at the exit of the MHD channel becomes lower than unity. For the optimum back pressure, high enthalpy extraction ratio is achieved and the adiabatic efficiency at the diffuser exit is decreased by several percent from that evaluated at the MHD channel exit. © 2000 Scripta Technica, Electr Eng Jpn, 133(2): 11–19, 2000     

Energy storage system utilizing large‐capacity electric double‐layer capacitors for peak‐cut of power demand

Recently, due to a rapid increase of demand for air conditioning in summer, peak power demand is becoming increasingly acute. Therefore, the load factor has a tendency to drop every year. The drop of the load factor is leading to a drop in the utilization factor of the power facilities and an increase in the cost of installation. In this paper, we propose an energy storage system for peak‐cut of power demand, in which we use large‐capacity electric double‐layer capacitors. This energy storage system has some distinctive characteristics, including long life span, maintenance‐free operation, preservation of environment, high efficiency at charge/discharge, and so on. This paper deals with the circuit arrangement of the proposed energy storage system, the charge equalization method of the capacitors, and the control method of the converter at charge/discharge. Finally, the operating characteristics of this system are evaluated by simulation analysis. © 2000 Scripta Technica, Electr Eng Jpn, 133(3): 83‐92, 2000     

Fault current limiting system for 500‐kV power systems

Recently, expansion in the scale of power systems and development of localized power sources are leading to an increase in fault current of 500‐kV systems. In the future, it is quite likely that the fault current at the interconnection of such power systems may exceed the rated short‐time current of existing electric power facilities. As one of the solutions of this problem, a thyristor‐controlled series‐resonant‐type fault current limiter (FCL) is proposed to restrain the fault current. This paper deals with the FCL system configuration, the placement method of the FCL in power systems, the outline of the FCL's specification, and the operation method of the protective relay in the multimachine system. Finally, the effectiveness of the FCL is evaluated from the viewpoints of limiting the fault current by simulation analysis. The FCL is shown to be a useful protection device for large, high‐capacity power systems. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 11–22, 1999