Biocompatible Cubic Boron Nitride: A Noncytotoxic Ultrahard Material

Cubic boron nitride (c-BN) has an ultrahardness and a large bandgap energy like diamond. In the last 30 years, most of the attention has been directed towards the mechanical and electronic applications of c-BN, while its biological potential has been overlooked. The authors report in vitro biocompatibility of high-quality c-BN films prepared by plasma-enhanced chemical vapor deposition using the chemistry of fluorine. c-BN films become superhydrophilic when chemical-treated in hydrogen and nitrogen plasmas with or without the impact of low-energy ions due to a marked increase in polar part of the surface free energy by removal of the fluorine atoms terminating c-BN surfaces. Satisfactory proliferation and differentiation of osteoblastic cells comparable with a control sample and a superhydrophilic nanocrystalline diamond film, and the formation of mineral deposits by biomineralization are confirmed on the superhydrophilic c-BN films with negative values of zeta potential. The results demonstrate a high potential of c-BN as a noncytotoxic ultrahard coating material for biological and biomedical applications.     

The Fe3O4-formation by the ‘Ferrite Process’: Oxidation of the reactive Fe(OH)2 suspension induced by sucrose

A mechanism of the formation of small particles of iron oxide in the wastewater treatment system ‘Ferrite Process’ is described. Small particles consisting of the Fe₃O₄−γ-Fe₂O₃ solid solution having slightly higher content of γ-Fe₂O₃ were obtained by the aerial oxidation of Fe(OH)₂ suspension in the presence of a weak dispersing reagent, sucrose, at pH 9.0. The increase of γ-Fe₂O₃ content is caused by a further oxidation of the Fe₃O₄ particles in the course of the reaction. The further oxidation was accelerated below 1000 Å of the particle size. When SO²⁻₄ ion coexisted with sucrose in the reaction medium, the further oxidation was reduced and the treatment of the wastewater was improved. At a temperature interval of 40°–65°C, the formation of α-FeOOH was completely inhibited by a small amount of sucrose and only Fe₃O₄ was obtained.     

A design and simulation tool for ground source heat pump system using energy piles with large diameter

Calculation of the underground temperature resulting from heat injection/extraction into/from ground heat exchangers (GHEXs) with hourly variation is one of the most noteworthy challenges to address when simulating and designing a ground source heat pump (GSHP). In order to overcome this challenge, the authors introduce a method to calculate the underground temperature, by considering heat injection/extraction into/from GHEXs with hourly variation. The method applies the superposition of the infinite cylindrical source (ICS) solution and the infinite line source (ILS) solution to calculate the temperature change due to heat injection/extraction into/from the considered GHEX and other neighboring GHEXs, respectively. The calculation method also considers heat injection/extraction from GHEXs with different heat injection/extraction rates and is able to accommodate GHEXs with large diameters such as energy piles. The calculation method was evaluated by applying it to calculate the temperature variation of the heat carrier fluid in a GSHP system with energy piles.     

Integrated reproduction of human motion components by motion copying system

Currently, the development of leading‐edge technology for recording and loading human motion on the basis of haptic information is required in the fields of manufacturing and human support. Human movement is an assembly of motion components. Since human movements should be supported by a robot in real time, it is necessary to integrate the motion components that were saved earlier. Once such motion integration is realized, future technology for use in daily human life can be developed. This paper proposes the integrated reproduction of the decomposed components of human motion by using a motion copying system. This system is the key technology for the realization of the acquisition, saving, and reproduction of real‐world haptic information. By using the proposed method, it is possible not only to achieve expert skill acquisition, skill transfer to robots, and power assist for each motion component, but also to open up new areas of applications. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(1): 28–35, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21263     

Fabrication of dense β-calcium orthophosphate with submicrometer-sized grains and its high-temperature superplastic deformation

High-density β-calcium orthophosphate (β-Ca₃(PO₄)₂, also called β-tricalcium phosphate: β-TCP) ceramics with submicrometer-sized grains were fabricated using a pulse-current pressure firing route. The maximum relative density of the β-TCP compacts was 98.7% at 1050 °C and this was accompanied by a translucent appearance. The mean grain size of the β-TCP compacts increased slightly with temperature to reach 0.78 μm at 1000 °C. However, upon further increasing the firing temperature to 1050 °C the mean grain size increased significantly to 1.6 μm. The extent of plastic deformation during tensile testing was examined at temperatures between 900 and 1100 °C using a strain rate in the range 9.26 × 10⁻⁵ to 4.44 × 10⁻⁴ s⁻¹. The maximum tensile strain achieved was 145% for a test temperature of 1000 °C and strain rate of 1.48 × 10⁻⁴ s⁻¹ and this was attributed to the relatively high density and small grain size.     

Fabrication and characterization of poly‐γ‐glutamic acid nanofiber

Poly‐γ‐glutamic acid (γ‐PGA) is a natural polymer that is widely recognized as a component in the viscous filaments of fermented soybean (natto). γ‐PGA is known for its superior biodegradability, biocompatibility and water retention characteristics. Crosslinked γ‐PGA is commonly used as a hydrogel, but it is not used in the fiber form because it is soluble in water. In this study, we demonstrate the use of γ‐PGA‐Na for production of water insoluble γ‐PGA nanofibers by electrospinning. This result was accomplished using an aqueous solvent containing 10 wt % of an oxazoline component polymer as the crosslinking agent and by heat treatment. The crosslinking reaction was evaluated by solid‐state NMR. The nanofiber webs showed a high level of moisture absorption capability while retaining their fibrous shape. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

MgSrSi-Type Compounds as a Possible New Family of Thermoelectric Materials

We calculated electronic structures and transport properties of 33 Zintl phase compounds M¹M²X (M¹, M² = Li, Na, Mg, K, Ca, Rb, Sr, Ba; X = Si, Ge, As, Se, Sn, Sb, Te, Pb, Bi) having orthorhombic MgSrSi-type (PbCl₂-type) structure. These compounds were calculated to be narrow-gap semiconductors or semimetals. By comparison with known thermoelectric materials, our analysis showed that these compounds are promising candidate new thermoelectric materials, when heavily doped with holes or electrons. The weak chemical bonds and the variety in constituent elements indicate the possibility to achieve high thermoelectric figure of merit.     

Control of Thermal Conductance of Peltier Device Using Heat Disturbance Observer

In industry, temperature control and heat flow control are now applied in many thermal devices, including Peltier devices, which facilitates heat transfer by the Peltier effect. Generally, temperature control compensates for heat flowing from the external environment, while heat actively flows into the system during heat flow control. Thus, temperature control and heat flow control differ from each other. However, there have been no detailed discussions of a thermal control process in which the thermal conductance control ranges between 0 and ∞. This paper focuses on thermal conductance control and the construction of a thermal conductance control system for a Peltier device using a heat disturbance observer. When using the thermal conductance controller, the thermal conductance control is altered and the system becomes thermally compliant with the external environment. This paper also presents experimental results that confirm the validity of the proposed control system. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(4): 44–52, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22411     

Effect of the preparation condition on the properties of titania-silica derived from tetraisopropyl titanate(IV) and tetraethyl orthosilicate

Titania-silica mixed oxide was prepared by hydrolyzing tetraethyl orthosilicate and tetraisopropyl titanate(IV) with a mixture of ethanol and 0.01 N aqueous acetic acid. Surface Ti content, BET surface area, and the number of acid sites increased with an increase in 0.01 N aqueous acetic acid. Thus hydrolysis of both alkoxides occurred simultaneously with a large amount of the acetic acid solution, and there was extensive interaction between TiO₂ and SiO₂ phases. With small amount of 0.01 N aqueous acetic acid, however, titanium hydroxide was first formed and, then, it was covered with the silica phase produced in a later stage of the hydrolysis. Increase in the acetic acid solution also led to the formation of a large amount of tetrahedral Ti species, which were active for the epoxidation of oct-1-ene usingt-butyl hydroperoxide as an oxidant.     

A 10 Gb/s optical heterodyne detection experiment using a 23 GHzbandwidth balanced receiver

A balanced receiver for multigigabit-per-second coherent optical transmission systems is described. A balanced optical receiver with a frequency bandwidth of 23 GHz is achieved by connecting an InGaAs twin-p-i-n photodiode to a 0.5-30.0 GHz GaAs monolithic distributed amplifier fabricated with a soldier bump flip-chip interconnection technique. An experiment which demonstrated that this receiver has the potential for use in 10-Gb/s optical CPFSK (continuous-phase frequency shift keying) heterodyne detection systems was conducted