ABSTRACT
Atomic resolution at a low accelerating voltage with aberration correction is required to reduce the electron irradiation damage in scanning transmission electron microscopy imaging. However, the reduction in resolution caused by the diffraction limit becomes severe with increasing electron wavelength at low accelerating voltages. The developed aberration corrector can compensate for higher-order aberration in scanning transmission electron microscopy to expand the uniform phase angle. The resolution for imaging graphene at 30 kV is evaluated by changing the convergence angle for a probe-forming system with a higher-order aberration corrector. A single-carbon atom on graphene is successfully imaged at atomic resolution with a cold-field emission gun by dark-field imaging at an accelerating voltage of 30 kV.
ABSTRACT
An aberration-corrected electron microscope developed in CREST project has been applied for imaging atoms and clusters buried inside crystals. The resolution of the microscope in scanning transmission electron microscopy (STEM) has experimentally proved to be better than 47 pm by use of a cold-field emission gun at 300 kV. The high resolution has given an advantage for imaging light elements such as lithium atoms discriminating one by one. Moreover, a three-dimensional structure imaging has been demonstrated for dopant clusters by a sub-50 pm STEM, using its high depth resolution.
ABSTRACT
Aberrations up to the fifth-order were successfully measured using an autocorrelation function of the segmental areas of a Ronchigram. The method applied to aberration measurement in a newly developed 300kV microscope that is equipped with a spherical aberration corrector for probe-forming systems. The experimental Ronchigram agreed well with the simulated Ronchigram that was calculated by using the measured aberrations. The Ronchigram had an infinite magnification area with a half-angle of 50mrad, corresponding to the convergence angle of a uniform phase.
ABSTRACT
OBJECTIVES: We tested the feasibility and efficacy of primary stent implantation without Coumadin in 74 patients within 8 h of the onset of acute myocardial infarction. BACKGROUND: Although stent implantation in patients with effort angina provides better short- and long-term outcomes than balloon angioplasty, it is not clear whether primary stent implantation is applicable or effective in acute myocardial infarction. METHODS: Primary sent implantation was attempted when 1) the lesion was not located distally in the main coronary branches, 2) the coronary artery did not show any severe calcification or excessive bending proximal to the lesion on fluoroscopy, and 3) the arterial diameter was > or = 2.5 mm. The results (group S) were compared with those of primary balloon angioplasty (group P). Poststenting regimens contained ticlopidine and aspirin without Coumadin. Poststenting inflation was performed with > or = 12 atm. RESULTS: Stent implantation was successful in 72 patients. Stent thrombosis was noted in only one patient who was not given ticlopidine, aspirin or Coumadin. The rates of restenosis and frequency of major clinical events during the hospital period in groups S and P were 0% versus 13.2% (p = 0.007) and 2.8% versus 18.6% (p = 0.009), respectively. Kaplan-Meier analysis demonstrated that cumulative 90-day clinical event-free rates in groups P and S were 98.1 +/- 16.0% versus 79.4 +/- 43.7% (p = 0.0068), and that 180-day rates were 86.5 +/- 38.4% versus 64.2 +/- 49.7% (p = 0.014). CONCLUSIONS: Primary stent implantation can improve clinical outcomes of patients with acute myocardial infarction when the stent is dilated adequately and antiplatelet drugs are used.
