Influência do Extrato Pirolenhoso na germinação de Brachiaria brizantha cv. Piatã / Influence of Pirolenhoso Extract on the germination of Brachiaria brizantha cv. Piatan

Subproduto da carbonização da madeira, o Extrato Pirolenhoso vem sendo estudado como um promotor de germinação de várias culturas. O objetivo deste trabalho foi avaliar a germinação de Brachiaria britzantha cv. Piatã embebidas em diferentes concentrações e tempos do Extrato Pirolenhoso (EP). O experimento foi conduzido no Laboratório de Análise de Sementes localizado na Unidade Acadêmica Especializada em Ciências Agrárias (UAECIA). Os tratamentos consistiram em 5 concentrações do EP (0, 5, 10, 15 e 20%) e diferentes horas de imersão (1, 4, 8, 16 e 24 horas). Foram realizados os testes de germinação, primeira contagem de germinação, teste de emergência, índice de velocidade de emergência e o teste frio. A análise estatística foi realizada pelo Design Expert® Versão 7.0.0 (Stat-Ease, EUA). As sementes imersas em EP sofreram influência na velocidade da sua germinação. Entretanto em concentrações mais altas do licor, 20%, houve redução na sua taxa de germinação. No tratamento com 5% de EP, durante 18 horas de imersão, 60% das sementes emergiram, já o tratamento utilizando 20% de EP, durante 4 horas de imersão, apresentou mais de 70% de germinação em comparação com a testemunha. Logo, pode-se concluir que o Extrato Pirolenhoso atuou como um estimulador germinativo da espécie Brachiaria brizantha cv. Piatã

Combined fit to the spectrum and composition data measured by the Pierre Auger Observatory including magnetic horizon effects

The measurements by the Pierre Auger Observatory of the energy spectrum and mass composition of cosmic rays can be interpreted assuming the presence of two extragalactic source populations, one dominating the flux at energies above a few EeV and the other below. To fit the data ignoring magnetic field effects, the high-energy population needs to accelerate a mixture of nuclei with very hard spectra, at odds with the approximate E$^{-2}$ shape expected from diffusive shock acceleration. The presence of turbulent extragalactic magnetic fields in the region between the closest sources and the Earth can significantly modify the observed CR spectrum with respect to that emitted by the sources, reducing the flux of low-rigidity particles that reach the Earth. We here take into account this magnetic horizon effect in the combined fit of the spectrum and shower depth distributions, exploring the possibility that a spectrum for the high-energy population sources with a shape closer to E$^{-2}$ be able to explain the observations

A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universality

The Pierre Auger Observatory is the most sensitive detector to primary photons with energies above ∼0.2 EeV. It measures extensive air showers using a hybrid technique that combines a fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (X$_{max}$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon searches in different energy bands are performed. In particular, between threshold energies of 1-10 EeV, a new analysis technique has been developed by combining the FD-based measurement of X$_{max}$ with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy

Study on multi-ELVES in the Pierre Auger Observatory

Since 2013, the four sites of the Fluorescence Detector (FD) of the Pierre Auger Observatory record ELVES with a dedicated trigger. These UV light emissions are correlated to distant lightning strikes. The length of recorded traces has been increased from 100 μs (2013), to 300 μs (2014-16), to 900 μs (2017-present), to progressively extend the observation of the light emission towards the vertical of the causative lightning and beyond. A large fraction of the observed events shows double ELVES within the time window, and, in some cases, even more complex structures are observed. The nature of the multi-ELVES is not completely understood but may be related to the different types of lightning in which they are originated. For example, it is known that Narrow Bipolar Events can produce double ELVES, and Energetic In-cloud Pulses, occurring between the main negative and upper positive charge layer of clouds, can induce double and even quadruple ELVES in the ionosphere. This report shows the seasonal and daily dependence of the time gap, amplitude ratio, and correlation between the pulse widths of the peaks in a sample of 1000+ multi-ELVES events recorded during the period 2014-20. The events have been compared with data from other satellite and ground-based sensing devices to study the correlation of their properties with lightning observables such as altitude and polarity