Nickel-scandia-stabilized zirconia ͑Ni-ScSZ͒ cermet is one of the promising anodes for use in intermediate-temperature solid oxide fuel cells. Although ScSZ exhibits higher oxide-ion conductivity than yttria stabilized zirconia, the aging effects depending on the doping-concentration results in a decrease in conductivity. However, recent extensive research has clarified that the electrolyte with Ͼ10 mol % Sc 2 O 3 shows no decrease in conductivity. In this study, therefore, 10 mol % Sc 2 O 3 -ZrO 2 ͑10ScSZ͒ was used as the ionic conductor in the cermet anode. The degradation behaviors under various humidified conditions were investigated at 800°C on the basis of partial pressure of oxygen under both open-circuit and discharge conditions. The degradation was judged from the impedance spectra before and after oxidative treatments, such as a continuous discharge or an exposure to highly humidified fuel under the open-circuit condition. The Ni-10ScSZ cermet exhibited both reversible and irreversible changes in impedance spectra, depending on the steam concentration and passed current densities. It is noted that, even under the open-circuit condition, the irreversible degradation has occurred with supplying a gaseous mixture of 10% H 2 -20% H 2 O-N 2 balance ͑p O 2 = 1.72 ϫ 10 −18 atm͒, whereas the reversible change in interfacial resistance was observed in the case of 10% steam concentration ͑p O 2 = 4.29 ϫ 10 −19 atm͒.Solid oxide fuel cells ͑SOFCs͒ have a great potential as an energy conversion device due to their high efficiency and low emissions. This technology is in an advanced stage of development at present. However, the long-term stability of stacked cells is the most important requirement for practical use and needs to be improved with priority. Degradation of the fuel cell is characterized by a steady decrease in performance, which occurs over a period of time. The performance deterioration can be regarded as the sum of the aging process in each material, although the extent to which the process contributes has not been sufficiently clarified. 1 Many studies have been conducted to elucidate and resolve this issue with focusing on the material stability, i.e., the interfacial reactions between different components. [2][3][4][5] Nickel-zirconia cermets are the most widely and commonly used anodes in SOFCs. The addition of zirconia is necessary to support the Ni particles, to prevent the coarsening, and to make the thermal expansion coefficient of the anode compatible with the electrolyte. 6 The optimization of the cermet structure is a key factor to achieve better performance. Generally, SOFCs are operated at high fuel utilizations, and the downstream part of the cell is exposed to the severe conditions because of the depletion of fuel and the high steam concentration. In such actual conditions, the main problems observed are the oxidization and agglomeration of Ni during the long-term operation, which leads to a decrease in the triple-phase boundary and electronic conductivity. Moreover, several groups have ...
The mechanism of artificial and spontaneous metastases of tumor was analyzed in B16 melanoma cells and C57BL/6 mice by using anti-asialo GM1 antibody and anticancer agents. Single administrations of 500 micrograms anti-asialo GM1 antibody resulted in significantly decreased NK activity in spleen cells of C57BL/6 mice, lasting 10 days from the day following administration. Treatment with anti-asialo GM1 antibody never decreased the function of T lymphocytes measured by blastogenesis with phytohemagglutinin or T cell growth factor. The tumoricidal functions of activated macrophages but not of resident macrophages were decreased by in vivo treatment with anti-asialo GM1 antibody. The anti-asialo GM1 antibody was evaluated in terms of the enhancing effect on pulmonary metastases with regard to the timing of administration. Treatment with anti-asialo GM1 antibody 1 day before or on the day of tumor inoculation resulted in a substantial increase in the number of artificial pulmonary metastases. In the experimental system of spontaneous metastases, anti-asialo GM1 antibody most effectively increased the number of pulmonary metastases when administered 1-2 weeks before the removal of primary tumor, when the tumor cells are thought to be released into blood circulation from the primary site. In addition, accelerated growth of transplanted tumors at the primary site was observed in mice treated with anti-asialo GM1 antibody. These results strongly suggest that anti-asialo GM1 antibody enhances the incidence of in vivo tumor metastases and the growth of transplanted tumor mainly by suppressing the function of NK cells. The maximum effective dose (MED) of mitomycin C or its derivative (M-83) suppressed NK activity significantly, and pretreatment with these anticancer agents enhanced the growth of the artificial pulmonary and liver metastases. In contrast, the MED of cDDP showed no effect on the NK activity or the numbers of pulmonary and liver metastases. These results indicate that the depression of NK activity induced by chemotherapy results in the promotion of metastatic disease. From these studies it can be concluded that NK cells have a key role in the control of metastases of malignant disease, and that support of NK activity is very important for the prevention of metastases.
Fusarium oxysporum, a soilborne phytopathogenic fungus, produces endopolygalacturonase (PG) which has been suggested to be related to disease development. A polyclonal antibody (PAb) APG1 was prepared against purified PG from F. oxysporum f. sp. lycopersici race 2. By direct tissue-blotted immunobinding assay (DT-IBA) with the antibody, PG production by the pathogen in the stem of the host plant was confirmed. Degenerate primers were designed based on partial amino acid residue information for the PG protein from the fungus: part of the PG-encoding gene was obtained by PCR. Using TAIL-PCR, the complete gene encoding PG was cloned and sequenced. The structural gene comprises 1318 bp coding for 371 amino acids with a putative signal peptide of 22 amino acids, and the open reading frame is interrupted by four introns of 47, 51, 50, and 54bp. The deduced amino acid sequence of the mature protein showed 82.9, 29.0, 27.6, 14.2, and 26.9% homology with those of F. moniliforme PG, Cochliobolus carbonum PGNI, Aspergillus niger PG, A. oryzae PG, and Sclerotinia sclerotiorum PGI, respectively.
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