Effects of nitrogen on the electrical properties of sputtered SiCx films

The electrical properties of r.f.-sputtered SiC_x films were studied with a view to thermistor applications. When the sputtering was carried out in an argon atmosphere containing a small amount of nitrogen gas, the electrical properties were strongly affected by the amount of nitrogen gas. For small amounts, less than 2%–3% in concentration, both the resistance and the experimental constant B decreased very rapidly as the amount of nitrogen gas was increased. In contrast, for larger amounts, more than 2%–3% in concentration, both the resistance and B increased rapidly with increasing concentration of nitrogen gas. For all the films sputtered in an argon atmosphere containing various amounts of nitrogen gas up to 9% in concentration, B increased linearly with increasing temperature. From this characteristic, the following experimental equation which represents the dependence of the resistance R of the films on temperature T was obtained:

$\text{R = AT}{}^{\mathrm{?n}}\text{exp}\text{(}\text{m}\text{T}\text{)}$

where A, n and m are constants determined experimentally.     

The distribution of dietary plant sterols in serum lipoproteins and liver subcellular fractions of rats

Rats were fed plant sterols containing campesterol and β-sitosterol in the different proportions, and their distribution in serum lipoproteins and in liver subcellular fractions was determined. In serum lipoproteins, the percentage as well as the concentration of plant sterols increased with the increase in the density of lipoproteins. Thus, high density lipoprotein (HDL) contained the highest and very low density lipoprotein (VLDL), the lowest. Also, there were distinct differences in the ratio of campesterol to sitosterol among lipoproteins, it was the highest in VLDL and lowest in HDL. Quantitatively, more than 75% of campesterol and 80% of sitosterol were carried in HDL; the values were significantly different from those of cholesterol (ca. 70%) in relation to total cholesterol. The distribution of plant sterols in liver subcellular fractions was virtually the same with that of cholesterol. Both nuclei and microsomes contained approximately 40% of total plant stetols. A preliminary part of the study was presented at the First Congress of the Federation of Asian and Oceanian Biochemists in Nagoya, October 1977.     

Hydrocracking Brazilian Marlim vacuum residue with natural limonite. Part 1: catalytic activity of natural limonite

An experimental study examined the catalytic effects of natural Australian (AL) and Brazilian (BL) limonites used in hydrocracking Brazilian Marlim vacuum residue (ML-VR). The catalytic behavior of the limonites was compared with a conventional NiO-MoO₃-Al₂O₃ (NiMo) catalyst. Diphenylmethane (DPM) and 1-methylnaphthalene (1-MN) were used as standards. The order in which coke and gas formation were suppressed during hydrocracking of ML-VR was NiMo>BL>AL, which is the same order as for the hydrogenation activity observed with the standard compounds. By contrast, the limonite catalysts exhibited relatively higher conversions and distillate yields in ML-VR hydrocracking than did the NiMo catalyst with the order of conversion and distillate yield (yield of the fraction with boiling point of 540 °C) being AL>BL>NiMo, which is the same order obtained for catalytic cracking of the two standards. Coke formation was effectively suppressed at high hydrogen pressures. The limonite catalysts showed lower activities for nitrogen and sulfur removal than did NiMo, but both proved to have a larger activity for nickel removal.     

Potential dependence of surface crystal structure of iron passive films in borate buffer solution

The effect of passivation potential on surface crystal structure, apparent thickness and passivity of oxide films formed on pure iron prepared by plasma sputter deposition was investigated. The crystallinity was improved with passivation potential and the width of atomically flat terraces was expanded to 6 nm when passivating at 750 mV for 15 min, as observed by ex situ scanning tunneling microscopy (STM) after aging in air (<30% RH). Apparent thickness and passivity are linearly dependent on passivation potential. The former weakly depends on passivation duration, the latter strongly depends on passivation duration. This is well explained by the correlation between crystal structure and passivity.     

A study on the cycle performance of lithium secondary batteries using lithium nickel-cobalt composite oxide and graphite/coke hybrid carbon

10 Wh-class (30650 type) lithium secondary batteries were fabricated using LiNi_0.7Co_0.3O₂ as the positive electrode material and graphite/coke hybrid carbon as the negative electrode material. In our previous work, we found that LiNi_0.7Co_0.3O₂ and graphite/coke hybrid carbon each provide a longer cycle life among several candidates (Kida et al., J. Power Sources 94 (2001) 74; Kida et al., in preparation; Kinoshita et al., J. Power Sources 102 (2001) 284). In this study, the cycle performance of cells using both LiNi_0.7Co_0.3O₂ and graphite/coke hybrid carbon was examined and the deterioration factor of the discharge capacity was investigated during charge/discharge tests. We then focused our interest on the negative electrode and analyzed it using ⁷Li nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). After the discharge capacity of the battery deteriorated to 70% of the rated capacity after 2000 cycles, the graphite/coke hybrid carbon showed 91% of initial discharge capacity. When the solid electrolyte interface (SEI) (LiF, Li₂CO₃ and polymers) (E. Peled, J. Electrochem. Soc. 126 (1979) 2047) on the carbon negative electrode became thicker in the charge/discharge cycle test, the impedance was considered to have increased. This suggests that the deterioration of the graphite/coke hybrid carbon material is not so large, but that the production of the SEI on the negative electrode and impedance change of the negative electrode are factors of the capacity fade.     

Evolution of passivity in air exposure of an iron passive film

The evolution of passivity in air exposure of air-formed films on as-polished bare irons and electrochemically reduced bare irons was investigated by electrochemical methods. Passivity and surface structure were characterized by the recovery duration against open-circuit breakdown and the spontaneous potential, respectively. A new factor, pre-exposure duration (t_pre, exposure duration prior to electrochemical treatments), was found to affect both surface structure and passivity of air-formed films. At t_pre < 20 min, the surface structures of air-formed films underwent a distinctly four-stage transformation in air exposure while the passivity of air-formed films underwent a two-stage transformation, being drastically improved after critical exposure duration in air. As a comparison, the surface structure of the passive film formed at −0.4 V for 30 min exhibited two-stage dependence on air exposure time, distinctly different from that of the air-formed films, and its passivity showed two-stage dependence on air exposure time. At t_pre < 20 min, the critical exposure duration for the passivity of air-formed films is 216.9 min, more than that (139.9 min) of the passive film while it is 19.1 min at t_pre > 6 h, in agreement with that (20.7 min) of the passive film. These results are explained by the dependence of the passivity on the crystal structure.     

Characterisation of HyperCoals from coals of various ranks

Ashless coals (HyperCoal) produced by thermal extraction of coals of different ranks with 1-methylnaphthalene at temperatures from 300 to 420 °C for 60 min were characterised. HyperCoal has many light components that are easily volatised and decomposed, and it has high thermal reactivity. All the HyperCoals showed high thermoplasticity during heating; in particular, HyperCoals obtained from low-rank Pasir and Mulia coals showed high thermoplasticity beginning at temperatures near 150 °C. On increasing the extraction temperature for Pasir sub-bituminous coal, the weight loss during heating decreased and the resolidification temperature shifted to higher temperatures. These results suggest that the Pasir-HyperCoal obtained at higher temperatures contains more, relatively heavy components. Nuclear magnetic resonance measurements showed that the ratio of aromatic carbon increased with increasing extraction temperature, indicating that some modification reactions occurred.     

Controlled release of argatroban from PLA film—Effect of hydroxylesters as additives on enhancement of drug release

The aim of this study was to develop a drug eluting stent that prevents vein restenosis. For this, we selected argatroban as the study drug and poly(lactic acid) (PLA) as the matrix. To enhance the release of argatroban from PLA film, the addition of hydroxylesters (additives) was investigated. The additives investigated were diethyl tartrate (DET), diethyl malate (DEM), and triethyl citrate (TEC). Marked enhancement of drug release was observed in DET-added film, while TEC- or DEM-added film showed little enhancement. To clarify the effect of DET, the release profile based on the contents of the drug and DET in the film and the effect of alkyl chain length of tartrate were studied. Tartrates used were dimethyl, di-i-propyl, and di-n-butyl esters (DMT, DiPT, and DnBT, respectively), and the enhancement order was DMT ≅ DET ≫ DiPT ≅ DBT ≅ PLA alone. The reasons for enhancement were discussed from the viewpoint of drug release behavior, degradation of PLA, water uptake within the film, and SEM observations. It was concluded that enhancement of drug release was due to large amounts of water uptake within the film which resulted in the formation of open pores at its surface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Transmission characteristics of WDM signals amplified by semiconductor optical amplifiers in the 1.3‐µm wavelength band

Applications of semiconductor optical amplifiers to wavelength division multiplexing systems in a 1.3‐µm wavelength band are studied. The measured characteristics of gain and noise figure of the SOA, with small dependency on polarization states, confirm that it is applicable to repeater amplifiers and preamplifiers. When it is used as the preamplifier of a nonrepeated two‐channel 10 Gb/s system, an allowable line loss of 32 dB is attained with the aid of another SOA used for the postamplifier. The measured bit‐error rate of a system with one repeater amplifier is well simulated from the individual characteristics of the SOA and the optical receiver. Using a similar technique, it is predicted that more than 10 amplifiers can be applied in a system with cascaded repeater amplifiers, on the assumption that the polarization dependency of the gain is ignored. © 1998 Scripta Technica, Electr Eng Jpn, 126(1): 23–33, 1999     

Novel active filter system composed of inverter bypass circuit for suppression of harmonic resonance

We have developed a novel harmonic compensation system consisting of shunt LC filters on the load side, a step‐down transformer on the receiving end, and a small‐capacity active filter with one end connected to the secondary winding of the transformer and the other to the load bus. The active filter which constitutes the bypass circuit for the main service transformer is current‐controlled to give adequate damping of the harmonic resonance caused by the inductance behind the load bus, especially at lower harmonic frequencies. We have installed this new compensation system in combination with a TCR‐type SVC and shunt LC filters at the Yamanashi Maglev Test Line. We present an outline of the reactive power and harmonic current compensation systems, and harmonic resonance test results which show satisfactory performance of the active filter. © 1999 Scripta Technica, Electr Eng Jpn, 129(1): 82–90, 1999