Graphene/Half-Metallic Heusler Alloy: A Novel Heterostructure toward High-Performance Graphene Spintronic Devices

Graphene-based vertical spin valves (SVs) are expected to offer a large magnetoresistance effect without impairing the electrical conductivity, which can pave the way for the next generation of high-speed and low-power-consumption storage and memory technologies. However, the graphene-based vertical SV has failed to prove its competence due to the lack of a graphene/ferromagnet heterostructure, which can provide highly efficient spin transport. Herein, the synthesis and spin-dependent electronic properties of a novel heterostructure consisting of single-layer graphene (SLG) and a half-metallic Co₂Fe(Ge_0.5Ga_0.5) (CFGG) Heusler alloy ferromagnet are reported. The growth of high-quality SLG with complete coverage by ultrahigh-vacuum chemical vapor deposition on a magnetron-sputtered single-crystalline CFGG thin film is demonstrated. The quasi-free-standing nature of SLG and robust magnetism of CFGG at the SLG/CFGG interface are revealed through depth-resolved X-ray magnetic circular dichroism spectroscopy. Density functional theory (DFT) calculation results indicate that the inherent electronic properties of SLG and CFGG such as the linear Dirac band and half-metallic band structure are preserved in the vicinity of the interface. These exciting findings suggest that the SLG/CFGG heterostructure possesses distinctive advantages over other reported graphene/ferromagnet heterostructures, for realizing effective transport of highly spin-polarized electrons in graphene-based vertical SV and other advanced spintronic devices.     

Development and Verification of a Plant Navigation System Displaying Symptom-Based Procedure

A plant navigation system has been developed to assist supervisors in nuclear power plants by automatically displaying the plant situation and plant operating procedures on a CRT screen when abnormalities occur. The goal suitable to the situation and the optimum operating procedures are automatically selected by using the diagnostic logic from the symptom-oriented procedure, on the basis of the current status of the plant, and are expressed by a flow and tree-type diagram like the problem analysis diagram. Verification tests have been performed twice using three scenarios, and the ability to maintain the quality for response to abnormalities by any type of supervisor has been confirmed.     

Photoinduced ionic conductivity in poly(ethylene glycol) containing malachite green leuco hydroxide

Summary Photoinduced ionic conductivity in poly(ethylene glycol) 400 (PEG400)/malachite green leuco hydroxide (MGLOH) was analyzed with photochemical reaction of MGLOH in its matrix. The resonance structure in photogenerated cation lay in the favor of 4,4-(dimethylamino) triphenylmethylcation (MG⁺) under UV irradiation. The change in the ionic conductivity was discussed with that in glass transition temperature (Tg) of the matrix on UV irradiation.     

Role of supercritical carbon dioxide for selective impregnation of decrosslinking reagent into isoprene rubber vulcanizate

The behavior of supercritical CO₂ (scCO₂)/low molar mass molecule/crosslinked rubber ternary system was investigated in relation to the impregnation of reagent into the isoprene rubber (IR) vulcanizates, which was the first step of new decrosslinking reaction. The diffusion coefficient of decrosslinking reagent, diphenyl disulfide (DD), into the IR network in scCO₂ was 3.2×10⁻¹¹ m²/s. The distribution coefficient (K_c) of DD between the solvent and IR matrix was also determined for scCO₂ and toluene. The K_c for scCO₂ was higher about four orders of magnitude than that for toluene. DD was uniformly dispersed in the crosslinked IR matrix under 10 MPa at 313 K in scCO₂. These phenomena are advantages of use of scCO₂ for the effective decrosslinking reaction of IR vulcanizate.     

Determination of the Contact Angle of a Liquid Droplet on a Carbon Fiber

This paper describes an improved method for the accurate determination of the contact angle of a liquid droplet on a monofilament. Theoretically, in this improved method, contact angles do not depend on droplet size or the radius of the fiber. The accuracy of this method is thus expected to be higher than any other standard methods.     

Vulcanization of 1-chlorobutadiene–butadiene rubber with diepoxy compound

Diepoxy vulcanization system of 1-chlorobutadiene–butadiene rubber(CB–BR) having hydroxyl groups with diglycidyl ether of bisphenol A (DGEBA) was studied in the presence of acid anhydrides. Phthalic anhydride (PAn), hexahydrophthalic anhydride (HAn), maleic anhydride (MAn), and succinic anhydride (SAn) were investigated as occuring agents. The results of this investigation indicated that the hydroxyl groups attached to the polybutadiene backbone react with DGEBA to afford a CB–BR vulcanizate rate depended on the kinds of acid anhydrides in the following order: PAn > MAn > SAn > HAn. It is assumed that the reaction between the hydroxyl group in CB–BR and acid anhydride was the rate-determining step. The vulcanization of CB–BR with a higher amount of DGEBA afforded resinous rubber vulcanizates. Thus, DGEBA was concluded to act not only as a curing agent, but also as a reinforcing agent for CB–BR. © 1995 John Wiley & Sons, Inc.     

Gender-related difference, geographical variation and time trend in dietary cadmium intake in Japan

OBJECTIVES: The present analysis was initiated to examine possible gender-dependency, geographic variation, and time-dependent changes in dietary intake of cadmium (Cd-F) among general populations in Cd-non-polluted areas in Japan. The role of rice as Cd-F source was also within the scope. METHODS: Two databases on Cd and nutritional analyses were re-visited. Both databases were established through collection of 24-h food duplicate portion samples from residents in areas with no known Cd pollution, and contained information on Cd and energy contents in the duplicate portion, together with daily rice consumption, the gender, the age and the location of the residence of each sample donor. The first and the second databases were established through surveys in the years around 1980 on 564 cases and around 1995 on 702 cases, respectively. The two databases were combined for evaluation by multiple regression (MRA) and other analyses. RESULTS: The analyses showed that men tended to take more Cd than women, more clearly so in the 1980 survey than in the 1995 survey. When Cd-F in the 1995 survey was compared with that in the 1980 survey, a substantial decrease was observed, e.g. by 30% (from 37.5 to 26.2 microg/day) in case of women. Cd-F values varied subject to the survey sites in a wide range (e.g. from 20 to 86 microg/day among women in the 1980 survey). In MRA with Cd-F as a dependent variable and survey sites and food intake factors (e.g. rice and energy intakes) as independent variables, the survey sites could explain more than 53% and 35% of total variation in Cd-F in the 1980 and 1995 surveys, respectively. Rice consumption was also influential to Cd-F in both surveys with partial correlation coefficients of 0.36 and 0.21, respectively, the influence being stronger in the 1980 survey than in the 1995 survey. A significant correlation was detected between the 1980 and 1995 survey results both in Cd-F and in rice consumption. CONCLUSION: Geographic and gender-related differences, and time-dependent decrease in dietary Cd intake in Japan were detected through analyses of food duplicate-based databases. The leading role of rice as dietary Cd source was also observed.     

Exposure to the mixtures of organic compounds in homes in Japan

The aim of the study reported herein was to characterize occupants' simultaneous exposure to mixtures of organic compounds in homes. Statistical distributions for concentrations of 28 organic compounds (17 VOCs and 11 aldehydes) measured in 1417 homes were generated to analyze concentration distributions. Three candidate distributions were identified for fitting the measured data: log-normal, exponential and gamma distributions. It appears from the results of fitting tests that gamma distributions are capable of representing 28 compound concentrations. Probability distributions show that formaldehyde and acetaldehyde ranged from 25 to 220 microg/m3 at 90% probabilities and most VOCs ranged from 3 to 80 microg/m3 at 90% probabilities. In order to characterize the occupant's exposure to the mixtures, the joint probability distributions of organic compounds were generated from the best-fitted distributions of individual compounds under the assumption that concentrations of organic compounds are mutually independent in homes. These joint distributions provided the statistical data for characterizing the occupant's exposure to the mixtures of organic compounds in homes. PRACTICAL IMPLICATIONS: Occupants often encounter not just one compound in indoor environments, but many compounds due to their concurrent emissions from several sources. This paper describes characteristics of statistical distributions for concentrations of 17 VOCs and 11 aldehydes in homes in Japan. After applying a probability model to the occupants' simultaneous exposure to mixtures of organic compounds, the authors interpret the current state of the occupant's exposure to the mixtures within homes using joint probability distributions of 28 organic compounds.     

Fabrication of Cryogenic Readout Circuits with n-type GaAs-JFETs for Low Temperature Detectors

We present the design and fabrication of cryogenic readout integrated circuits (ROICs) for Superconducting Tunneling Junctions using the SONY n-type GaAs-JFETs, which have good current-voltage characteristics and low noise performance even at <1 K. In order to fabricate the ROICs, we have designed simple GaAs-JFET amplifiers based on the measurement results of the GaAs-JFETs at <4.2 K: source follower amplifier, common source amplifier, and two types of cascode amplifiers. The obtainable gain of the cascode active load amplifiers is >100. These amplifiers were fabricated with the other circuit elements as an integrated circuit. We also show initial test results of the cascode active load amplifier.     

Electronic ferroelectricity from charge ordering in RFe(2)O(4)

We report our recent discovery of novel ferroelectricity arising from the polar ordering of Fe(3)+ and Fe(2)+ in a mixed valence triangular lattice oxide LuFe(2)O(4), where the electric polarization is not a result of ionic displacement. The polar ordering of Fe(3)+ and Fe(2)+ was confirmed with a resonant x-ray scattering study in SPring-8. The origin of such ordering is the competitive interaction between Fe(3)+ and Fe(2)+ in the triangular lattice, i.e., the charge frustration. The polar superlattice of Fe(3)+ and Fe(2)+ develops below 350 K, where the electric polarization appears. The ferroelectricity arising from the polar charge ordering or the polar electron distribution may have great potential for the future application of ferroelectrics.