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  • Author or Editor: T. Hayakawa x
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In order to identify novel peptide signaling molecules involved in the regulation of developmental and physiological processes in the freshwater cnidarian, Hydra magnipapillata , we initiated a systematic peptide screening project, the Hydra Peptide Project. In the project, twelve neuropeptides were identified so far. The LWamide family is composed of seven members, which share a GLWamide motif at their C-termini. All the peptides have an ability to induce metamorphosis of Hydractinia serrata planula larvae into polyps. In Hydra , LWamides induce detachment of the bud from a parental polyp. A neuropeptide, Hym-355, enhances neuronal differentiation by inducing the multipotent interstitial stem cells to enter the neuron differentiation pathway. A myoactive neutopeptide, Hym-176, specifically and reversibly induces contraction of the ectodermal muscle of the body column, in particularly in the peduncle region of epithelial Hydra that totally lack nerve cells. Two members of a novel neuropeptide family (FRamides) were contained in the same precursor. However, they have opposite myoactive functions in epithelial hydra. From these results, it seems fair to say reasonable to conclude that the so-called ‘primitive’; nervous system of Hydra is in reality more complex than generally believed.

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A comparison method, utilizing neutron activation analysis followed by multidimensional spectrum analysis was proven to provide accurate quantification of the multi-element samples. In this study, 23 elements were detected simultaneously in a sample containing standard elements for neutron activation analysis. The method presented here can be applied for about 50 elements.

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Perovskite oxides of composition (Sr1-xCax)(Fe0.5Co0.5)O3- were investigated for CO2 absorption properties and were proved to be useful as materials for CO2 absorption in the temperature range from 550 to 850 °C. The absorption rate of CO2 increased with Ca doping. The mechanical treatment of perovskite oxides for several minutes, especially for the oxides containing a small amount of Ca, was found to be effective for activating the oxides for CO2 absorption and for reducing the starting temperature of CO2 absorption by about 80 °C. However, it was not less effective to treat the oxides for a long time. The site distortion due to Sr and Ca ions at site A and the mixed valence states at site B were confirmed to be effective for CO2 absorption at high temperatures. During the absorption of CO2, a spinel compound was formed according to the following reaction: 2(Sr,Ca)(Fe,Co)O2.5 + CO2 (Sr,Ca)CO3 + (Sr,Ca)(Fe,Co)2O4.

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Feasibility of the method of multidimensional -ray spectrometer for neutron activation analysis was examined. Reference igneous rock (JP-1, JB-1a and JB-1) samples issued by the Geological Survey of Japan (GSJ) and the Allende meteorite reference sample were irradiated in a research reactor, and multiple -rays from the produced radioisotopes via neutron capture reactions were measured using an array of twelve germanium detectors with BGO Compton suppressors called GEMINI. Simultaneously thirty elements were observed with no chemical separation. The observed smallest component was Eu contained in JP-1 with abundance of 4 ppb.

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Multiparameter coincidence g-ray spectrometry based on g-g coincidence is widely used in the field of nuclear structure studies, and has produced many succesful results. In this paper, feasibility of the method for neutron activation analysis of trace elements was studied. Particularly, a long-lived radioisotope 129I (T1/2 = 1.57.107 y) in algae samples and iridium in geological samples has been determined.

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Neutron activation analysis with multi-parameter coincidence method was developed at the Japan Atomic Energy Agency (JAEA) and a non-destructive, ultra-high sensitive multi-elemental determination has been realized. The multi-parameter coincidence method is carried out with an array of 19 germanium detectors, GEMINI-II. Using this system, very weak γ-rays emitted from trace amounts of elements can be detected. The presolar grains were extracted from the Allende meteorite. Trace elements in the presolar diamonds were measured by neutron activation analysis with multi-parameter coincidence method.

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Sr0.95Ca0.05Fe0.5Co0.5O3- and Sr0.5Ca0.5Fe0.5Co0.5O3- perovskites were studied by 57Fe emission Mössbauer spectroscopy. It was found that Co prefers lower valence and lower coordination number than Fe in both compounds. The comparison of the emission and transmission Mössbauer spectra of the CO2 treated materials revealed a preferred formation of Fe-containing products in reaction with CO2 in Sr0.5Ca0.5Fe0.5Co0.5O3- , and it is proposed that such a reaction can be responsible for phase separation in Sr0.95Ca0.05Fe0.5Co0.5O3– after absorption and partial desorption of CO2 at 950 °C.

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