The biotransformation of endomorphin-1 (EM-1) by brain synaptic membranes has been studied. Peptide fragments of EM-1 that were formed during incubation with membrane preparations in vitro were isolated by High-performance liquid chromatography (HPLC) and characterized using determination of amino acid composition. At pH 7.4, two degradation products, EM-1(1-3) and EM-1(1-2), were identified. EM-1 was degraded 77.5% at 30 min incubation with synaptic membranes. The time course of the experiments and the effect of carboxypeptidase inhibitor (CPI) demonstrated that the proteolysis reaction involves the participation of carboxypeptidase activity.
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We demonstrate the imaging of the extended defects in Si materials using a focused ion beam instrument. Since Ga-ion beam has small penetration depth and high channeling character compared with electron beam, the secondary electron signal of focused ion beam is more sensitive to the surface morphology and crystallinity. We have tried to use this secondary electron imaging of focused ion beam for observation of various extended defects in Si materials for photovoltaic and semiconductor devices. As for the texture of multicrystalline Si, some grains are imaged darker than the others. It suggests that the crystal orientation gives different channeling effect on the primary Ga-ion beam, resulting in the different secondary electron yield. The grain boundaries and lineage in multicrystalline Si are shown as bright lines and patterns in the image. Although it may reflect the surface morphologies, these contrasts may be attributed to the channeling contrast due to lattice displacement or distortion. The contrast mechanism of FIB imaging is discussed.
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We have studied the dislocation generation and propagation from the seed crystals during seed cast Si growth. The grown ingot was cut into a vertical wafer, followed by the dislocation imaging using X-ray topography and Secco etching. The dislocation behavior at the seed area was compared with the dislocation generation at the top surface due to the thermal stress during cooling. The dislocations at the seed/crystal interface have propagated on the {111} plane toward top. When the seed surface was not melted sufficiently, the interface defect density became high, but no clear dislocation propagation was recognized. This suggests that the thermal shock at the seed/melt interface was not high enough to propagate dislocations to the growth direction. A certain amount of dislocations has been introduced from the top into the ingot according to the thermal stress. These observations suggest that optimizing the initial growth condition is important to dislocation control.
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