This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Recently, 3-D TEMs have been developed and 3-D structures of cell organelles, viruses and compound macromolecules have been obtained. The ultra-HVEM with a maximum accelerating voltage of 3.5MV has high penetration power for biological samples, and organic sections as thick as several micrometers can be observed at a high resolution of about one thousandth of the thickness. The thickness dependence of the resolution can be estimated by comparing an experimental image with a series of standard images on which a Gaussian-type point spread function with different standard deviations was superposed. An example of the results at 2MV is shown in Fig.1. This figure shows that ultra-HVEM can hold high resolution even at a high-angle tilt (i.e. at large thickness of specimen), and this is advantageous in the CT method.
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