Relic Neutrino Absorption Spectroscopy

Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang relic anti-neutrinos (and vice versa) into Z-bosons leads to sizable absorption dips in the neutrino flux to be observed at Earth. The high-energy edges of these dips are fixed, via the resonance energies, by the neutrino masses alone. Their depths are determined by the cosmic neutrino background density, by the cosmological parameters determining the expansion rate of the universe, and by the large redshift history of the cosmic neutrino sources. We investigate the possibility of determining the existence of the cosmic neutrino background within the next decade from a measurement of these absorption dips in the neutrino flux. As a by-product, we study the prospects to infer the absolute neutrino mass scale. We find that, with the presently planned neutrino detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant energy regime above 10^{21} eV, relic neutrino absorption spectroscopy becomes a realistic possibility. It requires, however, the existence of extremely powerful neutrino sources, which should be opaque to nucleons and high-energy photons to evade present constraints. Furthermore, the neutrino mass spectrum must be quasi-degenerate to optimize the dip, which implies m_{nu} >~ 0.1 eV for the lightest neutrino. With a second generation of neutrino detectors, these demanding requirements can be relaxed considerably.Comment: 19 pages, 26 figures, REVTeX

Efeitos da Salmonella Enteritidis experimentalmente inoculada na saúde gastrintestinal de perus Effects of experimentally inoculated Salmonella Enteritidis on the gastrointestinal health of turkeys

Avaliaram-se os efeitos de Salmonella Enteritidis sobre a colonização e o desenvolvimento do trato intestinal, a conversão alimentar e o ganho de peso em perus. Um total de 135 perus de corte de 1 dia foi distribuído em três tratamentos: controle; perus oriundos de ovos inoculados com Salmonella Enteritidis via casca e perus desafiados com água de bebida com Salmonella Enteritidis. Aos 10, 20 e 28 dias, avaliaram-se as variáveis de desempenho e coletaram-se amostras para avaliação bacteriana, biometria e histomorfometria. Realizaram-se também, nos dias 1, 15 e 28 de idade, coletas de mecônio/excretas de todas as aves. A colonização intestinal aumentou durante a fase inicial quando Salmonella foi inoculada via casca. O intestino apresentou maior peso ao 1º, 10º e 28º dias quando Salmonella esteve presente, sem diferença no comprimento. Salmonella Enteritidis foi capaz de colonizar o trato intestinal, estabelecer infecção, reduzir o desempenho das aves e modificar as estruturas celulares do intestino. A contaminação da casca do ovo antes da incubação propiciou a ocorrência de infecções ao nascimento, e a frequência de isolamento de Salmonella Enteritidis persistiu até 28 dias de idade. A inoculação de Salmonella pela água de bebida gerou aves infectadas, porém com menor nível de infecção com o avançar da idade. O desempenho de aves inoculadas com Salmonella Enteritidis é menor e isso confirma potenciais prejuízos para a produção avícola.<br>The effects of Salmonella Enteritidis on the colonization and development of the intestinal tract, feed conversion and weight gain were evaluated. A total of 135 day old turkeys were assigned to three treatments: control; turkeys from eggs inoculated with Salmonella Enteritidis via shell and turkeys challenged with drinking water with Salmonella Enteritidis. At 10, 20 and 28 days, the performance variables were evaluated and samples were collected to perform bacterial assessment, biometrics and histomorphometry. On days one, 15 and 28, samples of meconium/excreta were collected from all birds. The intestinal colonization increased during the initial phase when Salmonella was inoculated via eggshell. The intestine showed greater weight on the first, tenth and 28th days when Salmonella was present, with no differences regarding the intestine length. Salmonella Enteritidis was able to colonize the intestinal tract, establish infection, reduce bird performance and modify the cellular structures of the intestine. Contamination of the eggshell before hatching generated birds susceptible to infection at birth and the frequency of isolation of Salmonella Enteritidis persisted until 28 days of age. Salmonella inoculation by drinking water generated infected birds, but with less recovery of the pathogen with age increase. Inoculated birds showed inferior performance, confirming the potential damage to poultry production