331 research outputs found
Heavy boson production through the collision of an ultrahigh-energy neutrino on a target nucleon
We discuss W and Z production through the deep inelastic neutrino-nucleon
scattering in the context of the standard model SU(3)x SU(2)x U(1) of the
strong and electroweak interactions. We find the cross section rates for the
process neutrino + nucleon --> lepton(-) + W(+) + X for the case of
ultrahigh-energy neutrinos colliding on a target nucleon.Comment: 20 pages, 6 figure
Identification of an interferon-stimulated gene, isg15, involved in host immune defense against viral infections in gilthead seabream (Sparus aurata L.)
Interferons (IFNs) play a key role in the innate immunity of vertebrates against viral infections by inducing
hundreds of IFN-stimulated genes (ISGs), such as isg15. Isg15 is an ubiquitin-like protein, which can conjugate
cellular and viral proteins in a process called ISGylation, although it can also act as a cytokine-like protein.
Gilthead seabream (Sparus aurata L.) is an important asymptomatic carrier of viral haemorrhagic septicaemia
virus (VHSV) and nodavirus, representing a threat to other co-cultivated susceptible species. In order to better
understand virus-host interactions in this fish species, this study addresses the identification and molecular
characterization of seabream isg15 (sb-isg15). In addition, the modulation of transcript levels of sb-isg15 was
analysed in SAF-1 cells and seabream acidophilic granulocytes (AGs) stimulated in vitro with different pathogenassociated
molecular patterns (PAMPs) or inoculated with VHSV and striped jack nervous necrosis virus
(SJNNV).
The full-length cDNA of sb-isg15 gene, encoding a predicted protein of 155 amino acids, was identified and
seen to share the same characteristics as other fish and mammalian isg15 genes. Here we report the clear induction
of sb-isg15 transcript levels in SAF-1 cells and AGs stimulated with toll-like receptor (TLR) ligands, such
as polyinosinic:polycytidylic acid (poly I:C) or genomic DNA from Vibrio anguillarum (VaDNA), respectively.
Furthermore, VHSV and SJNNV inoculation induced a significant degree of sb-isg15 transcription in SAF-1 cells
and AGs. However, the relative levels of viral RNA transcription showed that SJNNV replication seems to be
more efficient than VHSV in both in vitro systems. Interestingly, sb-isg15 transcript induction elicited by VaDNA
was reduced in VHSV- and SJNNV-inoculated AGs, suggesting an interference prompted by the viruses against
the type I IFN system. Taken together, these findings support the use of seabream AGs as a valuable experimental
system to study virus-host interactions, in which sb-isg15 seems to play an important role.VersiĂłn del edito
Fabry Perot Halpha Observations of the Barred Spiral NGC 3367
We report the gross properties of the velocity field of the barred spiral
galaxy NGC 3367. The following values were found: inclination with respect to
the plane of the sky, i=30 deg; position angle (PA) of receding semi major axis
PA=51 and systemic velocity V(sys)=3032 km/s. Large velocity dispersion are
observed of upt o 120 km/s in the nuclear region, of up to 70 km/s near the
eastern bright sources just beyond the edge of the stellar bar where three
spiral arms seem to start and in the western bright sources at about 10 kpc.
Deviations from normal circular velocities are observed from all the disk but
mainly from the semi circle formed by the string of south western Halpha
sources. An estimate of the dynamical mass is M(dyn)=2x10^11 Msolar.Comment: Accepted to be published in May 2001 issue in the A.J. 19 pages, 7
figure
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
The Pierre Auger Collaboration has reported. evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > E-th = 5.5 x 10(19) eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > E-th are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above E-th/Z (for illustrative values of Z = 6, 13, 26). If the anisotropies above E-th are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies
The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays
Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found
The exposure of the hybrid detector of the Pierre Auger Observatory.
The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays. It consists of a surface array to measure secondary particles at ground level and a fluorescence detector to measure the development of air showers in the atmosphere above the array. The "hybrid" detection mode combines the information from the two subsystems. We describe the determination of the hybrid exposure for events observed by the fluorescence telescopes in coincidence with at least one water-Cherenkov detector of the surface array. A detailed knowledge of the time dependence of the detection operations is crucial for an accurate evaluation of the exposure. We discuss the relevance of monitoring data collected during operations, such as the status of the fluorescence detector, background light and atmospheric conditions, that are used in both simulation and reconstruction. (C) 2010 Elsevier B.V. All rights reserved
Measurement of the depth of maximum of extensive air showers above 10(18) eV
We describe the measurement of the depth of maximum, X-max, of the longitudinal development of air showers induced by cosmic rays. Almost 4000 events above 10(18) eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106 +/- 35-21) g/cm(2)/decade below 10(18.24) +/- (0.05) eV, and d24 +/- 3 g/cm(2)/ecade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm(2). The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed
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