1,853 research outputs found
Progresses in the validation of the FLUKA atmospheric neutrino flux calculations
The FLUKA calculation of the atmospheric neutrino fluxes have been
cross-checked by comparing predictions on lepton fluxes in atmosphere to
experimental data. The dependence of predicted neutrino fluxes on the shape and
normalization of primary spectrum is also investigatedComment: Presented at TAUP2001 (Sep. 8-12, Assergi, Italy). 5 pages, 1 figur
The hadronic models for cosmic ray physics: the FLUKA code solutions
FLUKA is a general purpose Monte Carlo transport and interaction code used
for fundamental physics and for a wide range of applications. These include
Cosmic Ray Physics (muons, neutrinos, EAS, underground physics), both for basic
research and applied studies in space and atmospheric flight dosimetry and
radiation damage. A review of the hadronic models available in FLUKA and
relevant for the description of cosmic ray air showers is presented in this
paper. Recent updates concerning these models are discussed. The FLUKA
capabilities in the simulation of the formation and propagation of EM and
hadronic showers in the Earth's atmosphere are shown.Comment: 8 pages, 9 figures. Invited talk presented by M.V. Garzelli at
ISVHECRI2006, International Symposium on Very High Energy Cosmic Rays,
Weihai, China, August 15 - 22 200
High energy extension of the FLUKA atmospheric neutrino flux
The atmospheric neutrino flux calculated with FLUKA was originally limited to
100-200 GeV for statistical reasons. In order to make it available for the
analysis of high energy events, like upward through-going muons detected by
neutrino telescopes, we have extended the calculation so to provide a reliable
neutrino yield per primary nucleon up to about 10**6 GeV/nucleon, as far as the
interaction model is concerned. We point out that the primary flux model above
100 GeV/nucleon still contributes with an important systematic error to the
neutrino flux.Comment: Extended version (10 pages) of the contribution to ICRC 2003, with
the addition of flux table
The FLUKA Monte Carlo, non-perturbative QCD and Cosmic Ray cascades
The FLUKA Monte Carlo code, presently used in cosmic ray physics, contains
packages to sample soft hadronic processes which are built according to the
Dual Parton Model. This is a phenomenological model capable of reproducing many
of the features of hadronic collisions in the non perturbative QCD regime. The
basic principles of the model are summarized and, as an example, the associated
Lambda-K production is discussed. This is a process which has some relevance
for the calculation of atmospheric neutrino fluxes.Comment: Extended version of the work for the proceedings of the workshop on
QCD at Cosmic Ray Energies, Erice, Aug. 30 - Sep. 4 2004, Ital
Atmospheric neutrinos in a Large Liquid Argon detector
In view of the evaluation of the physics goals of a large Liquid Argon TPC,
evolving from the ICARUS technology, we have studied the possibility of
performing precision measurements on atmospheric neutrinos. For this purpose we
have improved existing Monte Carlo neutrino event generators based on FLUKA and
NUX by including the 3-flavor oscillation formalism and the numerical treatment
of Earth matter effects. By means of these tools we have studied the
sensitivity in the measurement of Theta(23) through the accurate measurement of
electron neutrinos. The updated values for Delta m^2(23) from Super-Kamiokande
and the mixing parameters as obtained by solar and KamLand experiments have
been used as reference input, while different values of Theta(13) have been
considered. An exposure larger than 500 kton yr seems necessary in order to
achieve a significant result, provided that the present knowledge of systematic
uncertainties is largely improved.Comment: Talk given at the worksgop "Cryogenic Liquid Detectors for Future
Particle Physics", LNGS (Italy) March 13th-14th, 200
La medusa Craspedacusta sowerbyi en el embalse Río Tercero III, Córdoba, Argentina
Fil: Boltovskoy, Andrés. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Battistoni, Patricia A.. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin
A 3-Dimensional Calculation of Atmospheric Neutrino Flux
An extensive 3-dimensional Monte Carlo calculation of the atmospheric
neutrino flux is in progress with the FLUKA Monte Carlo code. The results are
compared to those obtained under the 1-dimensional approximation, where
secondary particles and decay products are assumed to be collinear to the
primary cosmic ray, as usually done in most of the already existing flux
calculations. It is shown that the collinear approximation gives rise to a
wrong angular distribution of neutrinos, essentially in the Sub-GeV region.
However, the angular smearing introduced by the experimental inability of
detecting recoils in neutrino interactions with nuclei is large enough to wash
out, in practice, most of the differences between 3-dimensional and
1-dimensional flux calculations. Therefore, the use of the collinear
approximation should have not introduced a significant bias in the
determination of the flavor oscillation parameters in current experiments.Comment: 27 pages, 14 figures. To be submitted to Astroparticle Physics. To be
submitted to Astroparticle Physic
Deregulation of transition metals homeostasis is a key feature of cadmium toxicity in Salmonella
Cadmium is a highly toxic metal whose presence in the environment represents a challenge for all forms of life. To improve our knowledge on cadmium toxicity, we have explored Salmonella Typhimurium responses to this metal. We have found that cadmium induces the concomitant expression of the cation efflux pump ZntA and of the high affinity zinc import system ZnuABC. This observation suggests that cadmium accumulation within the cell induces a condition of apparent zinc starvation, possibly due to the ability of this metal to compete with zinc for the metal binding site of proteins. This hypothesis is supported by the finding that strains lacking ZntA or ZnuABC are hyper-susceptible to cadmium and that the cadmium-induced growth defect of a znuABC mutant strain is largely relieved by zinc supplementation. A similar growth defect was observed for a mutant with impaired ability to acquire iron, whereas cadmium does not affect growth of a strain defective in manganese import. Cadmium also influences the expression and activity of the two cytoplasmic superoxide dismutases FeSOD and MnSOD, which are required to control cadmium-mediate oxidative stress. Exposure to cadmium causes a reduction of FeSOD activity in Salmonella wild type and the complete abrogation of its expression in the strain defective in iron import. In contrast, although MnSOD intracellular levels increase in response to cadmium, we observed discrepancies between protein levels and enzymatic activity which are suggestive of incorporation of non-catalytic metals in the active site or to cadmium-mediated inhibition of manganese import. Our results indicate that cadmium interferes with the ability of cells to manage transition metals and highlight the close interconnections between the homeostatic mechanisms regulating the intracellular levels of different metals
Extracellular glutathione decreases the ability of Burkholderia cenocepacia to penetrate into epithelial cells and to induce an inflammatory response
The airway surface liquid (ASL) of Cystic Fibrosis (CF) patients contains a lower concentration of reduced glutathione (GSH) with respect to healthy people. It is not known whether this defect may favor lung colonization by opportunistic pathogens
Competition for zinc binding in the host-pathogen interaction
Due to its favorable chemical properties, zinc is used as a structural or catalytic cofactor in a very large number of proteins. Despite the apparent abundance of this metal in all cell types, the intracellular pool of loosely bound zinc ions available for biological exchanges is in the picomolar range and nearly all zinc is tightly bound to proteins. In addition, to limit bacterial growth, some zinc-sequestering proteins are produced by eukaryotic hosts in response to infections. Therefore, to grow and multiply in the infected host, bacterial pathogens must produce high affinity zinc importers, such as the ZnuABC transporter which is present in most Gram-negative bacteria. Studies carried in different bacterial species have established that disruption of ZnuABC is usually associated with a remarkable loss of pathogenicity. The critical involvement of zinc in a plethora of metabolic and virulence pathways and the presence of very low number of zinc importers in most bacterial species mark zinc homeostasis as a very promising target for the development of novel antimicrobial strategies
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