243 research outputs found
Dethinning Extensive Air Shower Simulations
We describe a method for restoring information lost during statistical
thinning in extensive air shower simulations. By converting weighted particles
from thinned simulations to swarms of particles with similar characteristics,
we obtain a result that is essentially identical to the thinned shower, and
which is very similar to non-thinned simulations of showers. We call this
method dethinning. Using non-thinned showers on a large scale is impossible
because of unrealistic CPU time requirements, but with thinned showers that
have been dethinned, it is possible to carry out large-scale simulation studies
of the detector response for ultra-high energy cosmic ray surface arrays. The
dethinning method is described in detail and comparisons are presented with
parent thinned showers and with non-thinned showers
Personality Traits in Miners with Past Occupational Elemental Mercury Exposure
In this study, we evaluated the impact of long-term occupational exposure to elemental mercury vapor (Hg(0)) on the personality traits of ex-mercury miners. Study groups included 53 ex-miners previously exposed to Hg(0) and 53 age-matched controls. Miners and controls completed the self-reporting Eysenck Personality Questionnaire and the Emotional States Questionnaire. The relationship between the indices of past occupational exposure and the observed personality traits was evaluated using Pearsonâs correlation coefficient and on a subgroup level by machine learning methods (regression trees). The ex-mercury miners were intermittently exposed to Hg(0) for a period of 7â31 years. The means of exposure-cycle urine mercury (U-Hg) concentrations ranged from 20 to 120 ÎŒg/L. The results obtained indicate that ex-miners tend to be more introverted and sincere, more depressive, more rigid in expressing their emotions and are likely to have more negative self-concepts than controls, but no correlations were found with the indices of past occupational exposure. Despite certain limitations, results obtained by the regression tree suggest that higher alcohol consumption per se and long-term intermittent, moderate exposure to Hg(0) (exposure cycle mean U-Hg concentrations > 38.7 < 53.5 ÎŒg/L) in interaction with alcohol remain a plausible explanation for the depression associated with negative self-concept found in subgroups of ex-mercury miners. This could be one of the reason for the higher risk of suicide among miners of the Idrija Mercury Mine in the last 45 years
Simulation of Ultra-High Energy Photon Propagation in the Geomagnetic Field
The identification of primary photons or specifying stringent limits on the
photon flux is of major importance for understanding the origin of ultra-high
energy (UHE) cosmic rays. We present a new Monte Carlo program allowing
detailed studies of conversion and cascading of UHE photons in the geomagnetic
field. The program named PRESHOWER can be used both as an independent tool or
together with a shower simulation code. With the stand-alone version of the
code it is possible to investigate various properties of the particle cascade
induced by UHE photons interacting in the Earth's magnetic field before
entering the Earth's atmosphere. Combining this program with an extensive air
shower simulation code such as CORSIKA offers the possibility of investigating
signatures of photon-initiated showers. In particular, features can be studied
that help to discern such showers from the ones induced by hadrons. As an
illustration, calculations for the conditions of the southern part of the
Pierre Auger Observatory are presented.Comment: 41 pages, 9 figures, added references in introduction, corrected
energy in row 1 of Table 3, extended caption of Table
Muon content of ultra-high-energy air showers: Yakutsk data versus simulations
We analyse a sample of 33 extensive air showers (EAS) with estimated primary
energies above 2\cdot 10^{19} eV and high-quality muon data recorded by the
Yakutsk EAS array. We compare, event-by-event, the observed muon density to
that expected from CORSIKA simulations for primary protons and iron, using
SIBYLL and EPOS hadronic interaction models. The study suggests the presence of
two distinct hadronic components, ``light'' and ``heavy''. Simulations with
EPOS are in a good agreement with the expected composition in which the light
component corresponds to protons and the heavy component to iron-like nuclei.
With SYBILL, simulated muon densities for iron primaries are a factor of \sim
1.5 less than those observed for the heavy component, for the same
electromagnetic signal. Assuming two-component proton-iron composition and the
EPOS model, the fraction of protons with energies E>10^{19} eV is
0.52^{+0.19}_{-0.20} at 95% confidence level.Comment: 8 pages, 3 figures; v2: replaced with journal versio
Olfactory and trigeminal interaction of menthol and nicotine in humans
The purpose of the study was to investigate the interactions between two stimuliâmenthol and nicotineâboth of which activate the olfactory and the trigeminal system. More specifically, we wanted to know whether menthol at different concentrations modulates the perception of burning and stinging pain induced by nicotine stimuli in the human nose. The study followed an eightfold randomized, double-blind, cross-over design including 20 participants. Thirty phasic nicotine stimuli at one of the two concentrations (99 and 134Â ng/mL) were applied during the entire experiment every 1.5Â min for 1Â s; tonic menthol stimulation at one of the three concentrations (0.8, 1.5 and 3.4Â ÎŒg/mL) or no-menthol (placebo control conditions) was introduced after the 15th nicotine stimulus. The perceived intensities of nicotineâs burning and stinging pain sensations, as well as perceived intensities of mentholâs odor, cooling and pain sensations, were estimated using visual analog scales. Recorded estimates of stinging and burning sensations induced by nicotine initially decreased (first half of the experiment) probably due to adaptation/habituation. Tonic menthol stimulation did not change steady-state nicotine pain intensity estimates, neither for burning nor for stinging pain. Menthol-induced odor and cooling sensations were concentration dependent when combined with low-intensity nicotine stimuli. Surprisingly, this dose dependency was eliminated when combining menthol stimuli with high-intensity nicotine stimuli. There was no such nicotine effect on mentholâs pain sensation. In summary, we detected interactions caused by nicotine on menthol perception for odor and cooling but no effect was elicited by menthol on nicotine pain sensation
Universal lateral distribution of energy deposit in air showers and its application to shower reconstruction
The light intensity distribution in a shower image and its implications to
the primary energy reconstructed by the fluorescence technique are studied.
Based on detailed CORSIKA energy deposit simulations, a universal analytical
formula is derived for the lateral distribution of light in the shower image
and a correction factor is obtained to account for the fraction of shower light
falling into outlying pixels in the detector. The expected light profiles and
the corresponding correction of the primary shower energy are illustrated for
several typical event geometries. This correction of the shower energy can
exceed 10%, depending on shower geometry.Comment: 21 pages, 9 figure
First Results of Fast One-dimensional Hybrid Simulation of EAS Using CONEX
A hybrid simulation code is developed that is suited for fast one-dimensional
simulations of shower profiles, including fluctuations. It combines the Monte
Carlo simulation of high energy interactions with a fast numerical solution of
cascade equations for the resulting distributions of secondary particles.
Results obtained with this new code, called CONEX, are presented and compared
to CORSIKA predictions.Comment: 4 pages, 4 figures, to appear in the proceedings of the XIII
ISVHECRI, Pylos, 200
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
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