RESUMO
The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.
RESUMO
The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of nu(tau) at EeV energies. Assuming an E(nu)(-2) differential energy spectrum the limit set at 90% C.L. is E(nu)(2)dN(nu)(tau)/dE(nu)<1.3 x 10(-7) GeV cm(-2) s(-1) sr(-1) in the energy range 2 x 10(17) eV< E(nu)< 2 x 10(19) eV.
RESUMO
The problem of melaninogenesis and quinone tanning of the cuticle was examined by histochemical and biophysical methods (electroparamagnetic resonance: EPR) on normal subjects of Pycnoscelus surinamensis and on subjects with abnormal cuticular colour. The cuticle of abnormal subjects showed a lower content of polyphenolic substances and a greater positivity for the indole group. This suggests that in these insects tanning products can be synthetized differently and not derived from tyrosine but from tryptophan as postulated by Pryor (1955). Furthermore, a higher number of unsaturated aminic groups is found in abnormal subjects. Granules present only in the cytoplasm of the epidermal cells of the abnormal newly moulted subjects may indicate that the polyphenolic compound of tanning, secreted in an inactive form as 4-0, beta-glucoside, is not freed from the beta-glucosidase and remains as such in the cytoplasm.
Assuntos
Células Epidérmicas , Ortópteros/anatomia & histologia , Animais , Espectroscopia de Ressonância de Spin Eletrônica , Fenóis/análise , Pigmentação , Polímeros , Tirosina/análiseRESUMO
The problem of melaninogenesis and quinone tanning of the cuticle was examined by histochemical and biophysical methods (electroparamagnetic resonance: EPR) on normal subjects of Pycnoscelus surinamensis and on subjects with abnormal cuticular colour. The cuticle of abnormal subjects showed a lower content of polyphenolic substances and a greater positivity for the indole group. This suggests that in these insects tanning products can be synthetized differently and not derived from tyrosine but from tryptophan as postulated by Pryor (1955). Furthermore, a higher number of unsaturated aminic groups is found in abnormal subjects. Granules present only in the cytoplasm of the epidermal cells of the abnormal newly moulted subjects may indicate that the polyphenolic compound of tanning, secreted in an inactive form as 4-O, beta-glucoside, is not freed from the beta-glucosidase and remains as such in the cytoplasm.