267 research outputs found
Detection of ultra-high energy cosmic ray showers with a single-pixel fluorescence telescope
We present a concept for large-area, low-cost detection of ultra-high energy
cosmic rays (UHECRs) with a Fluorescence detector Array of Single-pixel
Telescopes (FAST), addressing the requirements for the next generation of UHECR
experiments. In the FAST design, a large field of view is covered by a few
pixels at the focal plane of a mirror or Fresnel lens. We report first results
of a FAST prototype installed at the Telescope Array site, consisting of a
single 200 mm photomultiplier tube at the focal plane of a 1 m Fresnel lens
system taken from the prototype of the JEM-EUSO experiment. The FAST prototype
took data for 19 nights, demonstrating remarkable operational stability. We
detected laser shots at distances of several kilometres as well as 16 highly
significant UHECR shower candidates.Comment: Accepted for publication in Astroparticle Physic
The Tully-Fisher Relation for 25,000 SDSS Galaxies as Function of Environment
We construct Tully-Fisher relationships (TFRs) in the , , , and
bands and stellar mass TFRs (smTFRs) for a sample of late spiral
type galaxies (with ) from the Sloan Digital Sky Survey (SDSS)
and study the effects of environment on the relation. We use SDSS-measured
Balmer emission line widths, , as a proxy for disc circular
velocity, . A priori it is not clear whether we can construct
accurate TFRs given the small diameter of the fibres used for SDSS
spectroscopic measurements. However, we show by modelling the H
emission profile as observed through a aperture that for galaxies at
appropriate redshifts () the fibres sample enough of the disc to
obtain a linear relationship between and ,
allowing us to obtain a TFR and to investigate dependence on other variables.
We also develop a methodology for distinguishing between astrophysical and
sample bias in the fibre TFR trends. We observe the well-known steepening of
the TFR in redder bands in our sample. We divide the sample of galaxies into
four equal groups using projected neighbour density () quartiles and
find no significant dependence on environment, extending previous work to a
wider range of environments and a much larger sample. Having demonstrated that
we can construct SDSS-based TFRs is very useful for future applications because
of the large sample size available.Comment: accepted for publication in MNRAS. 15 pages, 12 figure
Development of an enhanced bovine viral diarrhea virus subunit vaccine based on E2 glycoprotein fused to a single chain antibody which targets to antigen-presenting cells PALABRAS CLAVE
Abstract Bovine viral diarrhea virus (BVDV) is an important cause of economic losses worldwide. E2 is an immunodominant protein and a promising candidate to develop subunit vaccines. To improve its immunogenicity, a truncated E2 (tE2) was fused to a single chain antibody named APCH, which targets to antigen-presenting cells. APCH-tE2 and tE2 proteins were expressed in the baculovirus system and their immunogenicity was firstly compared in guinea pigs. APCH-tE2 vaccine was the best one to evoke a humoral response, and for this reason, it was selected for a cattle vaccination experiment. All the bovines immunized with 1.5 g of APCH-tE2 developed high levels of neutralizing antibodies against BVDV up to a year post-immunization, demonstrating its significant potential as a subunit vaccine. This novel vaccine is undergoing scale-up and was transferred to the private sector. Nowadays, it is being evaluated for registration as the first Argentinean subunit vaccine for cattle. PALABRAS CLAVE Glucoproteína E2; Anticuerpo de cadena simple; Vacuna a subunidad; Baculovirus; Desarrollo de una vacuna de subunidad BVDV mejorada basada en la glucoproteína E2 fusionada a un anticuerpo de cadena simple que se dirige a células presentadoras de antígeno Resumen El virus de la diarrea viral bovina (BVDV) es causante de importantes pérdidas económicas a nivel mundial. La proteína E2 es la inmunodominante del virus y es la candidata para desarrollar vacunas de subunidad. Para mejorar su inmunogenicidad, una versió
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
A search for point sources of EeV photons
Measurements of air showers made using the hybrid technique developed with
the fluorescence and surface detectors of the Pierre Auger Observatory allow a
sensitive search for point sources of EeV photons anywhere in the exposed sky.
A multivariate analysis reduces the background of hadronic cosmic rays. The
search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an
energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been
detected. An upper limit on the photon flux has been derived for every
direction. The mean value of the energy flux limit that results from this,
assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial
direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in
which EeV cosmic ray protons are emitted by non-transient sources in the
Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Reconstruction of inclined air showers detected with the Pierre Auger Observatory
We describe the method devised to reconstruct inclined cosmic-ray air showers
with zenith angles greater than detected with the surface array of
the Pierre Auger Observatory. The measured signals at the ground level are
fitted to muon density distributions predicted with atmospheric cascade models
to obtain the relative shower size as an overall normalization parameter. The
method is evaluated using simulated showers to test its performance. The energy
of the cosmic rays is calibrated using a sub-sample of events reconstructed
with both the fluorescence and surface array techniques. The reconstruction
method described here provides the basis of complementary analyses including an
independent measurement of the energy spectrum of ultra-high energy cosmic rays
using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (JCAP
Calibration of the Logarithmic-Periodic Dipole Antenna (LPDA) Radio Stations at the Pierre Auger Observatory using an Octocopter
An in-situ calibration of a logarithmic periodic dipole antenna with a
frequency coverage of 30 MHz to 80 MHz is performed. Such antennas are part of
a radio station system used for detection of cosmic ray induced air showers at
the Engineering Radio Array of the Pierre Auger Observatory, the so-called
Auger Engineering Radio Array (AERA). The directional and frequency
characteristics of the broadband antenna are investigated using a remotely
piloted aircraft (RPA) carrying a small transmitting antenna. The antenna
sensitivity is described by the vector effective length relating the measured
voltage with the electric-field components perpendicular to the incoming signal
direction. The horizontal and meridional components are determined with an
overall uncertainty of 7.4^{+0.9}_{-0.3} % and 10.3^{+2.8}_{-1.7} %
respectively. The measurement is used to correct a simulated response of the
frequency and directional response of the antenna. In addition, the influence
of the ground conductivity and permittivity on the antenna response is
simulated. Both have a negligible influence given the ground conditions
measured at the detector site. The overall uncertainties of the vector
effective length components result in an uncertainty of 8.8^{+2.1}_{-1.3} % in
the square root of the energy fluence for incoming signal directions with
zenith angles smaller than 60{\deg}.Comment: Published version. Updated online abstract only. Manuscript is
unchanged with respect to v2. 39 pages, 15 figures, 2 table
Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory
We report a multi-resolution search for anisotropies in the arrival
directions of cosmic rays detected at the Pierre Auger Observatory with local
zenith angles up to and energies in excess of 4 EeV ( eV). This search is conducted by measuring the angular power spectrum
and performing a needlet wavelet analysis in two independent energy ranges.
Both analyses are complementary since the angular power spectrum achieves a
better performance in identifying large-scale patterns while the needlet
wavelet analysis, considering the parameters used in this work, presents a
higher efficiency in detecting smaller-scale anisotropies, potentially
providing directional information on any observed anisotropies. No deviation
from isotropy is observed on any angular scale in the energy range between 4
and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured; while no
other deviation from isotropy is observed for moments beyond the dipole one.
The corresponding -values obtained after accounting for searches blindly
performed at several angular scales, are in the case of
the angular power spectrum, and in the case of the needlet
analysis. While these results are consistent with previous reports making use
of the same data set, they provide extensions of the previous works through the
thorough scans of the angular scales.Comment: Published version. Added journal reference and DOI. Added Report
Numbe
- …