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We study the evolution of the ionization state of the intergalactic medium (IGM) at the end of the reionization epoch using moderate resolution spectra of a sample of nineteen quasars at 5.74 < z em < 6.42 discovered in the Sloan Digital Sky Survey. Three methods are used to trace IGM properties: (a) the evolution of the Gunn-Peterson (GP) optical depth in the Lyα, β, and γ transitions; (b) the distribution of lengths of dark absorption gaps, and (c) the size of HII regions around luminous quasars. Using this large sample, we find that the evolution of the ionization state of the IGM accelerated at z > 5.7: the GP optical depth evolution changes from τ eff GP ∼ (1 + z) 4.3 to (1 + z) ∼ >11 , and the average length of dark gaps with τ > 3.5 increases from < 10 to > 80 comoving Mpc. The dispersion of IGM properties along different lines of sight also increases rapidly, implying fluctuations by a factor of ∼ > 4 in the UV background at 1 Based on observations obtained with the Sloan Digital Sky Survey; at the W.M. Keck Observatory, which is

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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 6.8×106 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 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena