Oscillatory neural activity associated with cognitive processes affected by spatial frequency

The spatial frequency contained in visual objects is known to affect human psychophysiology. In our previous study, we showed that event‐related potentials are affected by spatial frequency during a simple calculation task. In that study, however, we did not investigate the contribution of oscillatory neural activities. The purpose of the present study is to characterize the changes in oscillatory neural activity associated with cognitive processes, and to investigate how these signals are affected by the spatial frequency of a visual stimulus during simple calculation tasks. We investigate these issues by analyzing our previously collected electroencephalography (EEG) dataset using the same visual stimulus, tasks, subjects, and EEG recordings. In that study, four types of vertically striped visual stimuli were used. The visual stimuli contained embedded numbers (from 0 to 9) that possessed the following frequency (f) characteristics: white noise, 1/f, 1/f², and 1/f³. The subjects were instructed to perform two tasks: ‘add numbers’ (addition task) and ‘do not add numbers’ (reference task). EEG data were recorded, and event‐related synchronization (ERS) and desynchronization (ERD) for each visual stimulus were analyzed on the basis of the intertrial variances of wavelet coefficients for theta, alpha, low‐beta, and gamma band activity. Eight healthy men (21–23 years) were recruited to participate in the study. Our results suggest the presence of a frequency discrimination function in the theta band activity in the fronto‐central area at the latency of 198 ms during the addition task. The alpha‐band ERD during completion of the reference task also showed a spatial frequency dependency. This phenomenon was observed in the left temporal‐parietal area at a latency of 376 ms, and is thought to be related to the perceptual filter. We conclude that the observed changes in oscillatory neural activity associated with cognitive processes are affected by spatial frequency. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Production and properties of phytase and acid phosphatase from a sake koji mold, Aspergillus oryzae

We identified three types of acid phosphatase (ACP-I, ACP-II, and ACP-III) produced by Aspergillus oryzae in a submerged culture using only phytic acid as the phosphorous substrate. The optimum pH for the activities of the three enzymes was in the range of 4.5 to 5.5. Analysis of the substrate specificities of these enzymes revealed that ACP-I and ACP-III were acid phosphatases, and ACP-II was a phytase. These enzymes were produced during different periods of mycelial growth: ACP-II was produced during the early phase of cultivation (around 24 h), and ACP-I was produced between 24 to 72 h. ACP-III was detected after the production of ACP-I and ACP-II had ceased. The release of phosphate from phytic acid was expected to be due to the cooperative hydrolysis of these enzymes.     

Microstructure and densification of ZrB2–SiC composites prepared by spark plasma sintering

ZrB₂–SiC composites were prepared by spark plasma sintering (SPS) at temperatures of 1800–2100 °C for 180–300 s under a pressure of 20 MPa and at higher temperatures of above 2100 °C without a holding time under 10 MPa. Densification, microstructure and mechanical properties of ZrB₂–SiC composites were investigated. Fully dense ZrB₂–SiC composites containing 20–60 mass% SiC with a relative density of more than 99% were obtained at 2000 and 2100 °C for 180 s. Below 2120 °C, microstructures consisted of equiaxed ZrB₂ grains with a size of 2–5 μm and α-SiC grains with a size of 2–4 μm. Morphological change from equiaxed to elongated α-SiC grains was observed at higher temperatures. Vickers hardness of ZrB₂–SiC composites increased with increasing sintering temperature and SiC content up to 60 mass%, and ZrB₂–SiC composite containing 60 mass% SiC sintered at 2100 °C for 180 s had the highest value of 26.8 GPa. The highest fracture toughness was observed for ZrB₂–SiC composites containing 50 mass% SiC independent of sintering temperatures.     

Utilization of a Biodegradable Mulch Sheet Produced from Poly(Lactic Acid)/Ecoflex?/Modified Starch in Mandarin Orange Groves

We have developed a mulch sheet made by inflation molding of PLA, Ecoflex^® and modified starch, which all have different biodegradabilities. A field test of use as an agricultural mulch sheet for mandarin oranges was carried out over two years. The mechanical properties of the mulch sheet were weakened with time during the field test, but the quality of the mandarin oranges increased, a result of the controlled degradation of the sheet. The most degradable modified starch degraded first, allowing control of the moisture on the soil. Accelerator mass spectroscopy was used for evaluation of the biomass carbon ratio. The biomass carbon ratio decreased by degradation of the biobased materials, PLA and modified starch in the mulch sheet.     

Microstructural refinement of an As-cast Al-12.6 wt pct Si alloy by repeated thermomechanical treatment to produce a heavily deformable material

A certain degree of cold working is advantageous in developing a fine microstructure with minute silicon crystals for eutectic and/or hypereutectic Al-Si cast alloys. A novel process, repeated thermomechanical treatment (RTMT), was applied to an Al-12.6 wt pct Si cast alloy. The process involves multiple-pass cold working (less than a 20 pct reduction in section area) and heat treatment at 793 K for 3.6 ks. Cold-work annealing was repeated up to about an 80 pct reduction in section from the beginning. The RTMT material showed a refined microstructure with high ductility. Most silicon crystals were fragmented to only a few micrometers and were spheroidized. The RTMT material showed such marked plasticity that it could be wrought up to a 99 pct reduction in section at room temperature. The Cold-worked RTMT materials exhibited an excellent balance between tensile strength and elongation and a higher strain hardening than the cast material.     

Development of ultra-stable Ni catalysts for CO2 reforming of methane

Carbon deposition behavior in CO₂ reforming of methane, methane decomposition, and CO disproportionation on nickel-magnesia solid solution was investigated by means of thermogravimetric analysis and temperature programmed reaction of deposited carbon with carbon dioxide. It was found that rapid oxidation of CH_x on Ni surface by oxygen species from CO₂ through dissociation at metal-support interface is a key step for the inhibition of carbon formation.     

Power reduction techniques for a 1-Mb ECL-CMOS SRAM with an accesstime of 550 ps and an operating frequency of 900 MHz

This paper describes power reduction circuit techniques in an ultra-high-speed emitter-coupled logic (ECL)-CMOS SRAM. Introduction of a 0.25-μm MOS transistor allows a Y decoder and a bit-line driver to be composed of CMOS circuits, resulting in a power reduction of 34%. Moreover, a variable-impedance load has been proposed to reduce cycle time. A 1-Mb ECL-CMOS SRAM was developed by using these circuit techniques and 0.2-μm BiCMOS technology. The fabricated SRAM has an ultrafast access time of 550 ps and a high operating frequency of 900 MHz with a power dissipation of 43 W     

V–I characteristics of solid polymer electrolytic (SPE) dehumidifier

Measurements of the V–I characteristics of a solid polymer electrolytic (SPE) dehumidifier were done using a modified SPE dehumidifier with four electrodes which included two electrodes to carry the main current and the other two electrodes to measure the voltages applied to the electrical double layer, which are the boundary voltages between the electrodes and the SPE membrane. The measured results were analyzed using the Butler-Volmer equation to examine the validity of the measurements. The current flowing in the dehumidifier is produced by the decomposition of water near the anode. Therefore, under a steady-state condition, the current should be proportional to the supply rate of water to the anode. On the other hand, a two-layer model for the SPE dehumidifier presented in our previous article showed that the current flowing in the dehumidifier was roughly proportional to the water content in the vicinity of the anode. These results were introduced for interpretation of the V–I measurements of the SPE dehumidifier. It was concluded that the dehumidifier current was expressed in the form of a Butler-Volmer equation as a function of the electrode boundary voltages which were the voltages across the boundary between the electrodes and the SPE membrane. An experimental formula for the current under a steady-state condition was developed as a function of the water content near the anode and the boundary voltages.     

Nondestructive Quantitative Evaluation of Porosity Volume Distribution in Aluminum Alloy Die Castings by Fractal Analysis

The nondestructive and three-dimensional quantitative evaluation of porosity in aluminum alloy die castings is proposed to identify whether the predominant cause of pore formation is shrinkage or entrapped gas. The validity of this method of evaluation was shown by comparing two different regions with different ratios of pores formed by shrinkage and gas. It was shown that the proposed evaluation can be used as a quantitative indication of porosity.     

Controlling the drug release rate from biocompatible polymers with micro-patterned diamond-like carbon (DLC) coating

During the past year, we have witnessed the evolution of an intense public controversy regarding late thrombosis following implantation of drug eluting stent (DES) in patients with obstructive coronary artery disease. To overcome the problem, DES should possess sufficient biocompatibility and non-thrombogenicity with a controlled drug release system. A new DES composed of biocompatible polymers coated with antithrombogenic diamond-like carbon (DLC) coating was proposed. In this study, the drug release profile of the newly proposed drug eluting system was thoroughly investigated. Three polymers were selected as base drug-reservoir materials: hydrophilic 2-methacryloyloxyethyl phosphorylcholine (MPC), hydrophobic poly (ethylene-co-vinyl acetate) (EVA) and less hydrophobic polyurethane (PU). The three polymers are currently used or studied for biomedical materials, while MPC and DLC were already confirmed as excellent biocompatible materials with antithrombogenicity. After coating the lattice-like patterned DLC on both polymers containing drug, samples were soaked in 2 ml of medium of phosphate-buffered saline with 10% ethanol. The drug release rate was measured by a spectrophotometer. The percentile cover area of patterned DLC on polymers was varied from 0% (without DLC) to 100% (fully covered). The sample without DLC coating presented an initial burst of the drug release from the polymer matrix, whereas the DLC-coated samples inhibited the initial burst release from polymers within the first five days of the experiments. It was found that the drug eluting profiles could be effectively controlled by changing the cover area of micro-patterned DLC coatings on polymers, which may be applicable to the next-generation DES system that eventually prevents late thrombosis.