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A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250  GeV, but, from 20(More)
a r t i c l e i n f o The growth of magnesium on ruthenium has been studied by low-energy electron microscopy (LEEM) and scanning tunneling microscopy (STM). In LEEM, a layer-by-layer growth is observed except in the first monolayer, where the completion of the first layer in inferred by a clear peak in electron reflectivity. Desorption from the films is(More)
To the Editor: We wish to alert your readers to a potential problem with Ohmeda Tec 5 vaporizers. Tec 5 vaporizers are more prone to the pumping effect than Tec 4 vaporizers. The" pumping effect causes an increase in vapor output following a transient increase in back pressure. We became aware of this situation when we detected transient high-inspired(More)
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