We present the interpretation of the muon and scintillation signals of ultra-high-energy air showers observed by AGASA and Yakutsk extensive air shower array experiments. We consider case-by-case ten highest energy events with known muon content and conclude that at the 95% confidence level (C.L.) none of them was induced by a primary photon. Taking into account statistical fluctuations and differences in the energy estimation of proton and photon primaries, we derive an upper limit of 36% at 95% C.L. on the fraction of primary photons in the cosmic-ray flux above 10 20 eV. This result disfavors the Z-burst and superheavy dark-matter solutions to the GZK-cutoff problem.

The general approach disclosed herein opens the new possibilities of exploiting the oxidation processes followed by chemiluminescence (CL) emission for the assessment of an antioxidant potential of natural lipid materials and enables determination of the amount and strength of lipid-borne antioxidants in one experiment. The reliability of the analytical procedure is completely unaffected by an inevitable entering of oxidizable lipid portions into the probe chemiluminescent mixture, which is exemplarily illustrated for the case of vegetable oils which served as sources of antioxidant-containing lipids. As a matter of fact, the difference in the effective radical-scavenging rate constants, determined for the antioxidative constituents of the sunflower and corn oils, perfectly matches the distinction of their qualitative tocopherol contents. In addition to the antiradical activity of lipid samples, the antioxidant potential of the latter may be modified by their influence on hydroperoxide stability, as it has been also demonstrated in the present work.

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