We report a novel class of transmission electron microscope (TEM), the difference-contrast electron microscope (DTEM), which displays nanostructures of thin specimen objects in a topographical manner. Topography obtained by the difference-contrast develops shadowgraphs in pseudo three-dimension, namely volume-like representation of projected objects as if things are illuminated by light from one direction. The specific optical device tomanipulate electron waves for DTEM is the hemicircular π phase-plate, which appears to be quite distinguishable from the Zernike phase plate utilized in Zernike phase-contrast TEM, while both have to be placed onto the back-focal plane of the objective lens. The topographic images obtained with DTEM for ultrathin sections of kidney cells were compared with those obtained with conventional TEM. DTEM confirmed the experimental advantage of high contrast topography by visualizing ultrastructural details inside the cells.
A novel interarm interaction of DNA cruciform forming at inverted repeat sequence was characterized using an S1 nuclease digestion, permanganate oxidation, and microscopic imaging. An inverted repeat consisting of 17 bp complementary sequences was isolated from the bluegill sunfish Lepomis macrochirus (Perciformes) and subcloned into the pUC19 plasmid, after which the supercoiled recombinant plasmid was subjected to enzymatic and chemical modification. In high salt conditions (200 mM NaCl, or 100-200 mM KCl), S1 nuclease cut supercoiled DNA at the center of palindromic symmetry, suggesting the formation of DNA cruciform. On the other hand, S1 nuclease in the presence of 150 mM NaCl or less cleaved mainly the 3'-half of the repeat, thereby forming an unusual structure in which the 3'-half of the inverted repeat, but not the 5'-half, was retained as an unpaired strand. Permanganate oxidation profiles also supported the presence of single-stranded part in the 3'-half of the inverted repeat in addition to the center of the symmetry. Both electron microscopy and atomic force microscopy have detected a thick protrusion on the supercoiled DNA harboring the inverted repeat. We hypothesize that the cruciform hairpins at conditions favoring triplex formation adopt a parallel side-by-side orientation of the arms allowing the interaction between them supposedly stabilized by hydrogen bonding of base triads.
[7] have already been reported. These results, which are illustrating qualified high-contrast images, were obtained under the excellent condition of phase plates relatively free from contaminant charging. During observation, misalignment of the phase plate or specimen charging may cause the central beam to hit the phase plate. This induces severe contamination on the phase plate surface, which causes charging and the resultant image distortion. Hosokawa reported that heating phase plates to around 200ºC prevented contamination from possible sources such as vacuum pump oil or biological specimens [8]. This suggested that the phase plate with heating had to be free from contaminant charging if it was initially free from charging. The procedure to prepare an initially charge-free phase plate could follow a general method to eliminate electrostatic charging of TEM specimens, namely wrapping with conductive materials, particularly amorphous carbon, just before inserting the phase plate into the TEM column. We have reported how dramatically this procedure reduced contaminant charging of phase plates [3] (refer to Fig. 1).Five years after the solution proposed, still, we have occasionally been suffered from the unpredictable phase plate charging. The charging problem has also been observed for AB phase plates, which are made of only metallic materials wrapped with gold and heated to higher temperature. We have observed phase shift due to charging of gold-coated bar magnet at a high temperature over Curie point (refer to Fig. 2). These results indicate that there is such a charging process progressing even on such a TFPP or ABPP surface as free from organic contaminants. Recently we have found what the cause of the unpredictable process happening at high temperature is. An effort to remove the ultimate obstacle to realizing charging-free phase plates will be reported.
The aims of this study were to investigate the lateralization hypothesis of schizophrenia, comparing chronic schizophrenics with unilateral brain-damaged subjects and normal controls, using attentional tests sensitive to the unilateral brain damage. Three attentional tests with different modes of stimuli, two vigilance tasks that require the self-paced or nonself-paced responses of subjects and one divided attention task, were administered to 28 chronic schizophrenics, 26 right and 24 left unilateral brain-damaged subjects, and 20 normal controls. The results indicated that schizophrenics performed a possible right-hemisphere damages pattern and also a left pattern in part, with failure of all tasks to show either pattern related to a number of differences between the three tasks. Furthermore, the attention deficits of schizophrenics are less than those of brain-damaged subjects but are clearly abnormal compared with the normal controls.
A wireless axial pair resonator consists of two coils coupling inductively with a body coil, which is used as a signal transmitter and receiver. Computer simulations gave signal enhancements of 1.41 and 1.47 for the resonators of 15- and 20-cm diameter, whereas those of phantom studies gave 1.37 and 1.49.
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