2,053 research outputs found
Educational studies of cosmic rays with telescope of Geiger-Muller counters
A group of high school students (XII Liceum) in the framework of the Roland
Maze Project has built a compact telescope of three Geiger-Muller counters. The
connection between the telescope and PC computer was also created and programed
by students involved in the Project. This has allowed students to use their
equipment to perform serious scientific measurements concerning the single
cosmic ray muon flux at ground level and below. These measurements were then
analyzed with the programs based on the 'nowadays' knowledge on statistics. An
overview of the apparatus, methods and results were presented at several
students conferences and recently won the first prize in a national competition
of high school students scientific work. The telescope itself, in spite of its
'scientific' purposes, is built in such a way that it is hung on a wall in a
school physics lab and counts muons continuously. This can help to raise the
interest for studying physics among others. At present a few (3) groups of
young participants of the Roland Maze Project have already built their own
telescopes for their schools and some others are working on it. This work is a
perfect example of what can be done by young people when respective
opportunities are created by more experienced researchers and a little help and
advice is given.Comment: 5 figures, 10 page
Global Production Increased by Spatial Heterogeneity in a Population Dynamics Model
Spatial and temporal heterogeneity are often described as important factors having a strong impact on biodiversity. The effect of heterogeneity is in most cases analyzed by the response of biotic interactions such as competition of predation. It may also modify intrinsic population properties such as growth rate. Most of the studies are theoretic since it is often difficult to manipulate spatial heterogeneity in practice. Despite the large number of studies dealing with this topics, it is still difficult to understand how the heterogeneity affects populations dynamics. On the basis of a very simple model, this paper aims to explicitly provide a simple mechanism which can explain why spatial heterogeneity may be a favorable factor for production.We consider a two patch model and a logistic growth is assumed on each patch. A general condition on the migration rates and the local subpopulation growth rates is provided under which the total carrying capacity is higher than the sum of the local carrying capacities, which is not intuitive. As we illustrate, this result is robust under stochastic perturbations
TeV gamma-UHECR anisotropy by decaying nuclei in flight: first neutrino traces?
Ultra High Cosmic Rays) made by He-like lightest nuclei might solve the AUGER
extragalactic clustering along Cen A. Moreover He like UHECR nuclei cannot
arrive from Virgo because the light nuclei fragility and opacity above a few
Mpc, explaining the Virgo UHECR absence. UHECR signals are spreading along
Cen-A as observed because horizontal galactic arms magnetic fields, bending
them on vertical angles. Cen A events by He-like nuclei are deflected as much
as the observed clustered ones; proton will be more collimated while heavy
(iron) nuclei are too much dispersed. Such a light nuclei UHECR component
coexist with the other Auger heavy nuclei and with the Hires nucleon
composition. Remaining UHECR spread group may hint for correlations with other
gamma (MeV-Al^{26} radioactive) maps, mainly due to galactic SNR sources as
Vela pulsar, the brightest, nearest GeV source. Other nearest galactic gamma
sources show links with UHECR via TeV correlated maps. We suggest that UHECR
are also heavy radioactive galactic nuclei as Ni^{56}, Ni^{57} and Co^{60}
widely bent by galactic fields. UHECR radioactivity (in and
channels) and decay in flight at hundreds keV is boosted (by huge Lorentz
factor (nearly a billion) leading to PeVs electrons and consequent synchrotron
TeVs gamma offering UHECR-TeV correlated sky anisotropy. Moreover also rarest
and non-atmospheric electron and tau neutrinos secondaries at PeVs, as the
first two rarest shower just discovered in ICECUBE, maybe the first signature
of such expected radioactive secondary tail.Comment: 7 pages,3 figures. arXiv admin note: substantial text overlap with
arXiv:1201.015
Recommended from our members
Inducible interleukin-1 gene expression in human vascular smooth muscle cells.
Interleukin-1 (IL-1) mediates many components of generalized host response to injury and may also contribute to local vascular pathology during immune or inflammatory responses. Because altered function of smooth muscle cells (SMC) accompanies certain vascular diseases, we tested whether SMC themselves might produce this hormone. Unstimulated SMC contain little or no IL-1 mRNA. However, exposure to bacterial endotoxin caused accumulation of IL-1 mRNA in SMC cultured from human vessels. Endotoxin maximally increased IL-1 beta mRNA in SMC after 4-6 h. The lowest effective concentration of endotoxin was 10 pg/ml. 10 ng/ml produced maximal increases in IL-1 beta mRNA. Interleukin-1 alpha mRNA was detected when SMC were incubated with endotoxin under "superinduction" conditions with cycloheximide. Endotoxin-stimulated SMC also released biologically functional IL-1, measured as thymocyte costimulation activity inhibitable by anti-IL-1 antibody. Thus, human SMC can express IL-1 beta and IL-1 alpha genes, or very similar ones, and secrete biologically active product in response to a pathological stimulus. Endogenous local production of this inflammatory mediator by the blood vessel wall's major cell type could play an important early role in the pathogenesis of vasculitis and arteriosclerosis
Inelastic scattering of protons from He and Li in a folding model approach
The proton-inelastic scattering from He and Li nuclei are
studied in a folding model approach. A finite-range, momentum, density and
isospin dependent nucleon-nucleon interaction (SBM) is folded with realistic
density distributions of the above nuclei. The renormalization factors N
and N on the real and volume imaginary part of the folded potentials are
obtained by analyzing the respective elastic scattering data and kept unaltered
for the inelastic analysis at the same energy. The form factors are generated
by taking derivatives of the folded potentials and therefore required
renormalizations. The values are extracted by fitting the p +
He,Li inelastic angular distributions. The present analysis of
p + He inelastic scattering to the 3.57 MeV excited state, including
unpublished forward angle data (RIKEN) confirms L = 2 transition. Similar
analysis of the p + He inelastic scattering angular distribution leading to
the 1.8 MeV (L = 2) excited state fails to satisfactorily reproduce the data.Comment: one LaTeX file, five PostScript figure
The Sloan Lens ACS Survey. IX. Colors, Lensing and Stellar Masses of Early-type Galaxies
We present the current photometric dataset for the Sloan Lens ACS (SLACS)
Survey, including HST photometry from ACS, WFPC2, and NICMOS. These data have
enabled the confirmation of an additional 15 grade `A' (certain) lens systems,
bringing the number of SLACS grade `A' lenses to 85; including 13 grade `B'
(likely) systems, SLACS has identified nearly 100 lenses and lens candidates.
Approximately 80% of the grade `A' systems have elliptical morphologies while
~10% show spiral structure; the remaining lenses have lenticular morphologies.
Spectroscopic redshifts for the lens and source are available for every system,
making SLACS the largest homogeneous dataset of galaxy-scale lenses to date. We
have developed a novel Bayesian stellar population analysis code to determine
robust stellar masses with accurate error estimates. We apply this code to
deep, high-resolution HST imaging and determine stellar masses with typical
statistical errors of 0.1 dex; we find that these stellar masses are unbiased
compared to estimates obtained using SDSS photometry, provided that informative
priors are used. The stellar masses range from 10^10.5 to 10^11.8 M and
the typical stellar mass fraction within the Einstein radius is 0.4, assuming a
Chabrier IMF. The ensemble properties of the SLACS lens galaxies, e.g. stellar
masses and projected ellipticities, appear to be indistinguishable from other
SDSS galaxies with similar stellar velocity dispersions. This further supports
that SLACS lenses are representative of the overall population of massive
early-type galaxies with M* >~ 10^11 M, and are therefore an ideal
dataset to investigate the kpc-scale distribution of luminous and dark matter
in galaxies out to z ~ 0.5.Comment: 20 pages, 18 figures, 5 tables, published in Ap
A time frequency analysis of wave packet fractional revivals
We show that the time frequency analysis of the autocorrelation function is,
in many ways, a more appropriate tool to resolve fractional revivals of a wave
packet than the usual time domain analysis. This advantage is crucial in
reconstructing the initial state of the wave packet when its coherent structure
is short-lived and decays before it is fully revived. Our calculations are
based on the model example of fractional revivals in a Rydberg wave packet of
circular states. We end by providing an analytical investigation which fully
agrees with our numerical observations on the utility of time-frequency
analysis in the study of wave packet fractional revivals.Comment: 9 pages, 4 figure
Ultra High Energy Particles Propagation and the Transition from Galactic to Extra-Galactic Cosmic Rays
We discuss the basic features of the propagation of Ultra High Energy Cosmic
Rays in astrophysical backgrounds, comparing two alternative computation
schemes to compute the expected fluxes. We also discuss the issue of the
transition among galactic and extra-galactic cosmic rays using theoretical
results on fluxes to compare different models.Comment: 6 pages, 6 .eps figures, invited talk given at the 'International
Symposium on Future Directions in UHECR Physics', 13-16 February 2012, CERN,
Geneva (Switzerland
Search for single sources of ultra high energy cosmic rays on the sky
In this paper, we suggest a new way to identify single bright sources of
Ultra High Energy Cosmic Rays (UHECR) on the sky, on top of background. We look
for doublets of events at the highest energies, E > 6 x 10^19 eV, and identify
low energy tails, which are deflected by the Galactic Magnetic Field (GMF). For
the sources which are detected, we can recover their angular positions on the
sky within one degree from the real ones in 68% of cases. The reconstruction of
the deflection power of the regular GMF is strongly affected by the value of
the turbulent GMF. For typical values of 4 microG near the Earth, one can
reconstruct the deflection power with 25% precision in 68% of cases.Comment: 20 pages, 10 figures. Corresponds to the version published in JCA
Composition of UHECR and the Pierre Auger Observatory Spectrum
We fit the recently published Pierre Auger ultra-high energy cosmic ray
spectrum assuming that either nucleons or nuclei are emitted at the sources. We
consider the simplified cases of pure proton, or pure oxygen, or pure iron
injection. We perform an exhaustive scan in the source evolution factor, the
spectral index, the maximum energy of the source spectrum Z E_{max}, and the
minimum distance to the sources. We show that the Pierre Auger spectrum agrees
with any of the source compositions we assumed. For iron, in particular, there
are two distinct solutions with high and low E_{max} (e.g. 6.4 10^{20} eV and 2
10^{19} eV) respectively which could be distinguished by either a large
fraction or the near absence of proton primaries at the highest energies. We
raise the possibility that an iron dominated injected flux may be in line with
the latest composition measurement from the Pierre Auger Observatory where a
hint of heavy element dominance is seen.Comment: 19 pages, 6 figures (33 panels)- Uses iopart.cls and iopart12.clo- In
version 2: addition of a few sentences and two reference
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