Preparation and characteristics of a binderless carbon nanotube monolith and its biocompatibility

A carbon nanotube (CNT) monolith without any binders was obtained by spark plasma sintering (SPS) treatment at 1100 °C under 40 MPa pressure. Transmission electron microscope results confirmed that this material maintained the nanosized tube microstructure of raw CNT powder after SPS treatment. The density and mechanical properties of this material were similar to cancellous bone. The material was implanted in subcutaneous tissue and femurs of rats and tissue samples were analyzed by histopathology at 1 and 4 weeks after surgery. Although some foreign body giant cells were seen around the CNTs, no severe inflammatory response such as necrosis was observed, and CNT implants were surrounded by newly formed bone in the femur. The study provides the first in vivo testing evidence that pure bulk carbon nanotubes are not a strongly inflammatory substance and have no toxicity for bone regeneration. Our study is the first successful experiment to consolidate CNTs without binders, and may provide an effective method for CNT monolith synthesis, as well as demonstrating that a binderless carbon nanotube material with a strength matching that of bone could be a candidate bone substitute material and a bone tissue engineering scaffold material.     

Formaldehyde-limited cultivation of a newly isolated methylotrophic bacterium, Methylobacterium sp. MF1: enzymatic analysis related to C1 metabolism

Formaldehyde is a highly toxic compound to most living organisms. We have isolated a bacterial strain that is able to efficiently degrade formaldehyde and use it as a sole carbon source. The isolated strain was identified as Methylobacterium sp. MF1, which could grow on formaldehyde and methanol. Methylobacterium sp. MF1 was grown in batch culture using 1.2 g/l formaldehyde as a sole carbon source, which was all consumed within 200 h. In order to decompose formaldehyde more efficiently, formaldehyde-limited chemostat cultivation of Methylobacterium sp. MF1 was investigated. Formaldehyde was consumed at 1.7 g/l/d when the dilution rate was 0.012 h(-1). Under these conditions, the cell turbidity (OD610) reached 2.0. Furthermore, when the initial turbidity was adjusted to 3.0 using methanol-grown cells, continuous cultivation could be started at an initial dilution rate of 0.008 h(-1). Using these conditions, consumption of formaldehyde could be continued for at least 600 h. The enzyme activities of cells growing as a chemostat culture, using methanol or formaldehyde as a sole carbon source, were compared to that of C1 metabolism. No difference was detected in the enzyme activities for the oxidation and assimilation of C1 compounds between the two cell-free extracts. Furthermore, methanol dehydrogenase activity was detected at the same level when formaldehyde was used as a sole carbon source. These results suggest that the resistance to the toxic effects of formaldehyde exhibited by Methylobacterium sp. MF1 is related to factors other than C1 metabolism.     

Identification and properties of ultra-fine iron particles dispersed in a glass-like carbon matrix

Various kinds of iron particles and an iron species were synthesized from acetylferrocenefurfural resins in a glass-like carbon matrix by heat-treatment. These irons were investigated in terms of magnetic susceptibility, saturation magnetization, esr, and the Mössbauer effect. Body-centred cubic (b c c) iron, expanded b c c iron, hexagonal close-packed iron, and cluster iron were present as ultra-fine iron particles. The presence of Fe⁺ was well established as an iron species. The formation of iron particles and Fe⁺ is discussed on the basis of the pyrolysis of ferrocene skeletons in the resin.     

Fabrication of CNT-carbon composite microstructures using Si micromolding and pyrolysis

A fabrication method of carbon nanotube (CNT)-carbon composite microstructures has been developed. CNT-carbon composite microstructures with dimensions from 10 micrometers to several hundred micrometers have been fabricated by pyrolysis process from the patterned SU-8 photoresist mixed with 1 wt% of CNTs at temperature of ~600 °C under inert atmosphere. The resulting composite microstructures with a high aspect ratio of ~34 can be successfully fabricated by this novel fabrication method. This research provides a simple approach that is compatible with microfabrication technology and is capable of fabricating composite microstructures with reproducible shape and dimensions, at desired locations. This approach has potential for the further exploring of applications of composite micro/nano structures as functional units in various microdevices. Also the ultramicroindentation hardness of the CNT-carbon composite films was investigated by nanoindentation measurement.     

Induction-heated cooking appliance using new quasi-resonant ZVS-PWMinverter with power factor correction

This paper presents a new prototype of a voltage-fed quasi-load resonant inverter with a constant-frequency variable-power (CFVP) regulation scheme, which is developed for the next-generation high-frequency high-power induction-heated (IH) cooking appliances in household applications. This application-specific high-frequency single-ended push-pull inverter using new-generation specially designed insulated gate bipolar transistors (IGBTs) can efficiently operate under a principle of zero-voltage switching pulsewidth modulation (ZVS-PWM) strategy. This low-cost soft-switching inverter using reverse-conducting and reverse-blocking IGBTs is more suitable for multiple-burner-type induction-heating cooking appliances. The operating principle and unique features of a new resonant ZVS-PWM inverter circuit topology is originally described, together with its steady-state power regulation characteristics, which are illustrated on the basis of its computer-aided simulation and experimental results. The ZVS operation condition on power regulation, loss analysis of new IGBTs incorporated into this inverter, and its active filtering performance are discussed for IH cooking appliances     

Behavior navigation system for harsh environments

Performing general human behavior by experts’ navigation is expected to be realized as wearable technologies and computing systems are further developed. We have proposed and developed the prototype of the advanced behavior navigation system (BNS) using augmented reality technology. Utilizing the BNS, an expert can guide a non-expert to perform a variety of tasks. The BNSs are useful in tasks to be performed in harsh and hazardous environments, such as factories, construction sites, and areas affected by natural disasters (e.g. earthquakes and tsunamis). In this paper, we present a BNS that is specifically designed to operate in harsh environments, with characteristics such as wet or dusty conditions. The implementation, experimental results, and evaluation of the BNS prototypes are presented.     

Amorphous Electrically Actuating Submicron Fiber Waveguides

Amorphous electrically actuating submicron fiber waveguides are promising building blocks for creating novel opto‐electromechanical devices. In this study, waveguiding and electrically actuating properties of the waveguides composed of racemic poly(lactic acid) and a dye are investigated. The fibers have mean diameters of <0.4 µm, and each fiber demonstrates subwavelength waveguiding with a loss coefficient of 1.5 × 10^?4–8.3 × 10^?4 µm^?1 at 0.63 µm wavelength. Light propagates with a near‐light speed group velocity between wavelengths of 0.59 and 0.63 µm, where the fraction of power inside the core is 0.13–0.28. The fiber mat thicknesses change in response to both the polarity and the magnitude of an applied voltage, similar to the inverse‐piezoelectric effect. The estimated values for both the apparent piezoelectric constant (29 000 × 10^?12 m V^?1) and Young's modulus (1.5 kPa) indicate a high degree of electricity actuation and a soft mat. Extremely small, soft, and electrically actuating waveguides can produce novel opto‐electromechanical devices.     

Phase transformations in the B2 phase of Co-rich Co-Al binary alloys

Phase transformations in the β (B2) phase of Co-21 and -23 at.% Al alloys were examined using transmission electron microscopy, energy dispersive X-ray spectroscopy and differential scanning calorimetry. The microstructures obtained from as-quenched specimens were found to be strongly affected by the quenching condition. While relatively thick sheet-specimens with a lower quenching rate showed bainitic plate precipitates with a fcc structure, a martensite-like structure was observed by optical microscopy in relatively thin specimens with a higher quenching rate. Regardless of the quenching condition, a spinodal-like microstructure composed of A2 and B2 phases was also detected and the A2 phase changed to a metastable hcp phase during further aging.     

Design of narrow bandwidth ladder-type filters with sharp transition bands using mutually connected resonator elements

This paper proposes a new design technique for a ladder-type filter to reduce the passband width without sacrificing the insertion loss, out-of-band rejection, and steepness of the transition bands. First, it is shown that 2 transmission zeros can be generated by connecting an additional resonator in either series or parallel arm of the ladder filter topology. This new filter topology can be designed systematically by the derived-m transformation. Second, it is demonstrated that the narrow bandwidth, sharp transition bands, and large outof- band rejection are simultaneously realized by applying the present technique to specifically designed ladder-type filters. Finally, this technique is applied to the design of a SAW filter fabricated on the Cu-grating/15°YX-LiNbO₃ structure.