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Yamamoto S.,Kobe City College of Technology | Oohashi T.,Foundation for Advancement of International Science | Shimizu K.,Institute of Biological Research and Innovation | Senda M.,Institute of Biological Research and Innovation
IEEE Transactions on Nuclear Science | Year: 2011

Brain functional studies using PET have advantages over fMRI in some areas such as auditory research in part because PET systems produce no acoustic noise during acquisition. However commercially available PET systems are designed for whole body studies and are not optimized for brain functional studies. We developed a low cost, small, wearable brain PET system named PET-Hat dedicated for brain imaging. It employs double counter-balanced systems for mechanical supports of the detector ring while allowing the subject some freedom of motion. The motion enables subject to be measured in the sitting position and move relatively freely with the PET during acquisition. The detector consists of a Gd2SiO5 (GSO) block, a tapered light guide and a flat panel photomultiplier tube (FP-PMT). Two types of GSO are used for depth-of-interaction (DOI) separation allowing the use of a small ring diameter without resolution degradation. The tapered light guide allows the use of larger GSO blocks with fewer FP-PMTs. Sixteen detector blocks are arranged in a 280 mm diameter ring. Transaxial and axial field-of-view (FOV) are 20 cm and 4.8 cm, respectively. Energy resolution of the block detectors was ∼ 15% full width at half maximum (FWHM) and timing resolution was ∼ 4.6 ns FWHM. Transaxial resolution and axial resolution at the center of the FOV were ∼ 4.0 mm FWHM and ∼ 3.5 mm FWHM, respectively. Sensitivity was 0.7% at the center of the axial FOV. Scatter fraction was ∼ 0.6. Hoffman brain phantom images were successfully obtained. We conclude that the PET-Hat is a promising, low cost, small, wearable brain PET system for brain functional studies. © 2011 IEEE. Source

Foundation For Advancement Of International Science | Date: 2013-07-03

With respect to a vacuum tube having a reduced pressure vessel containing an electric discharge gas sealed therein, problems such as the lowering of discharge efficiency owing to an organic material, moisture or oxygen remaining in the reduced pressure vessel have taken place conventionally. It has been now found that the selection of the number of water molecules, the number of molecules of an organic gas and the number of oxygen molecules remaining in the reduced pressure vessel, in a relation with the number of molecules of a gas contributing the electric discharge allows the reduction of the adverse effect by the above-mentioned remaining gas. Specifically, the selection of the number of molecules of the above electric discharge gas being about ten times that of the above-mentioned remaining gas or more can reduce the adverse effect by the above-mentioned remaining gas.

Fukushima A.,Chiba University | Yagi R.,Tokyo Seitoku College | Kawai N.,Foundation for Advancement of International Science | Kawai N.,Waseda University | And 3 more authors.
PLoS ONE | Year: 2014

The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs) above the human audible range (max. 20 kHz) activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect. In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz) of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz) to observe changes in the alpha2 frequency component (10-13 Hz) of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG), which we previously reported as an index of the hypersonic effect. Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC). When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect), while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect). These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC. Source

Oohashi T.,Foundation for Advancement of International Science | Maekawa T.,Yokkaichi University | Ueno O.,Japan Science and Technology Agency | Kawai N.,Foundation for Advancement of International Science | And 2 more authors.
Artificial Life | Year: 2014

As part of our research on programmed self-decomposition, we formed the hypothesis that originally immortal terrestrial organisms evolve into ones that are programmed for autonomous death. We then conducted evolutionary simulation experiments in which we examined this hypothesis using an artificial ecosystem that we designed to resemble a terrestrial ecosystem endowed with artificial chemistry. Notable results corroborating our hypothesis were obtained, which showed that mortal organisms emerged from indigenous immortal organisms through mutation; such mortal organisms survived and left behind offspring, albeit very rarely, and, having survived, surpassed immortal organisms without exception. In this article, we report the details of the above findings and also discuss a background framework we previously constructed for approaching altruism. © 2013 Massachusetts Institute of Technology. Source

Shirai K.,Kyushu University | Inomata N.,Fukuoka Womens University | Mizoiri S.,Sekisui Chemical Tanzania Ltd. | Aibara M.,Foundation for Advancement of International Science | And 4 more authors.
Gene | Year: 2014

When a population size is reduced, genetic drift may fix slightly deleterious mutations, and an increase in nonsynonymous substitution is expected. It has been suggested that past aridity has seriously affected and decreased the populations of cichlid fishes in Lake Victoria, while geographical studies have shown that the water levels in Lake Tanganyika and Lake Malawi have remained fairly constant. The comparably stable environments in the latter two lakes might have kept the populations of cichlid fishes large enough to remove slightly deleterious mutations. The difference in the stability of cichlid fish population sizes between Lake Victoria and the Lakes Tanganyika and Malawi is expected to have caused differences in the nonsynonymous/synonymous ratio, ω (=. dN/. dS), of the evolutionary rate. Here, we estimated ω and compared it between the cichlids of the three lakes for 13 mitochondrial protein-coding genes using maximum likelihood methods. We found that the lineages of the cichlids in Lake Victoria had a significantly higher ω for several mitochondrial loci. Moreover, positive selection was indicated for several codons in the mtDNA of the Lake Victoria cichlid lineage. Our results indicate that both adaptive and slightly deleterious molecular evolution has taken place in the Lake Victoria cichlids' mtDNA genes, whose nonsynonymous sites are generally conserved. © 2014 Elsevier B.V. Source

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