183 research outputs found
ASPECTOS REPRODUTIVOS DO PEIXE-ZEBRA, Danio rerio, EXPOSTO A DOSES SUBLETAIS DE DELTAMETRINA
The deltamethrin is listed by the
Environmental Protection Agency of the United States
(USEPA) as a possible endocrine disruptor, being able
to interfere in the reproductive system. It is a synthetic
pyrethroid, with potent insecticide action, relatively low
toxicity in mammals and limited persistence in the
environment, but high toxic to aquatic organisms. It is
also used in the human and veterinary medicines for
prophylaxis and treatment of parasitic diseases. The aim
of this study was to evaluate possible endocrine
alterations in the reproduction of the zebrafish (Danio
rerio) following the protocol of USEPA (2002). The fish
were exposed to sublethal concentrations of deltamethrin
(6 µg/L and 10 µg/L of the technical deltamethrin) and
acetone, used as solvent, during 14 days. Parameters
as number of eggs, hatching, size and histology of the
gonads were evaluated. It was not observed any
significant difference of the evaluated parameters among
the groups. The deltamethrin didnt alter the reproduction
of the zebrafish. In the present study the progeny was
not evaluated, because was not included in the used
protocol. However, endocrine disruptor substances can
affect the neuroendocrine reproductive system and the
alterations can appear in the progenitors or in the
progeny in different stages of the development.A deltametrina está listada pela Agência
de Proteção Ambiental dos Estados Unidos (USEPA)
como possível desregulador endócrino, podendo,
portanto, interferir no sistema reprodutivo. É um
piretróide sintético, com ação inseticida, toxicidade
relativamente baixa para mamíferos e persistência
limitada no meio ambiente, mas de alta toxicidade para
organismos aquáticos. É também empregada nas
medicinas humana e veterinária para profilaxia e
tratamento de doenças parasitárias. O objetivo deste
estudo foi avaliar possíveis alterações na reprodução
do peixe zebra (Danio rerio) seguindo o protocolo da
USEPA (2002). Os peixes foram expostos a
concentrações subletais de deltametrina (6 µg/L e 10
µg/L) e à acetona (solvente), durante 14 dias.
Parâmetros como número de ovos, eclosão, índice
gônado-somático e histologia de gônadas foram
avaliados. Não foi possível observar nenhuma diferença
significativa dos parâmetros avaliados entre os grupos,
concluindo-se que a deltametrina não alterou a
reprodução da espécie estudada. Neste trabalho a
progênie não foi avaliada, pois não fazia parte do
protocolo proposto. Porém, as substâncias
desreguladoras endócrinas podem atuar afetando o
sistema neuroendócrino reprodutivo e estas alterações
podem apresentar-se tanto nos progenitores como na
progênie em diferentes etapas do desenvolvimento
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory
The advent of the Auger Engineering Radio Array (AERA) necessitates the
development of a powerful framework for the analysis of radio measurements of
cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air
shower radio emission in coincidence with the surface particle detectors and
fluorescence telescopes of the Pierre Auger Observatory, the radio analysis
functionality had to be incorporated in the existing hybrid analysis solutions
for fluoresence and surface detector data. This goal has been achieved in a
natural way by extending the existing Auger Offline software framework with
radio functionality. In this article, we lay out the design, highlights and
features of the radio extension implemented in the Auger Offline framework. Its
functionality has achieved a high degree of sophistication and offers advanced
features such as vectorial reconstruction of the electric field, advanced
signal processing algorithms, a transparent and efficient handling of FFTs, a
very detailed simulation of detector effects, and the read-in of multiple data
formats including data from various radio simulation codes. The source code of
this radio functionality can be made available to interested parties on
request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to
author list and references in v
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
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