365 research outputs found
Phase-resolved Crab pulsar measurements from 25 to 400 GeV with the MAGIC telescopes
We report on observations of the Crab pulsar with the MAGIC telescopes. Our
data were taken in both monoscopic (> 25GeV) and stereoscopic (> 50GeV)
observation modes. Two peaks were detected with both modes and phase-resolved
energy spectra were calculated. By comparing with Fermi- LAT measurements, we
find that the energy spectrum of the Crab pulsar does not follow a power law
with an exponential cutoff, but has an additional hard component, extending up
to at least 400 GeV. This suggests that the emission above 25 GeV is not
dominated by curvature radiation, as suggested in the standard scenarios of the
OG and SG models.Comment: 4 pages, 2 figures, Proc. TAUP 2011, submitted for publication in
JCP
VLBI and Single Dish Monitoring of 3C84 in the Period of 2009-2011
The radio galaxy 3C 84 is a representative of gamma-ray-bright misaligned
active galactic nuclei (AGNs) and one of the best laboratories to study the
radio properties of the sub-pc jet in connection with the gamma-ray emission.
In order to identify possible radio counterparts of the gamma-ray emissions in
3C 84, we study the change in structure within the central 1 pc and the light
curve of sub-pc-size components C1, C2, and C3. We search for any correlation
between changes in the radio components and the gamma-ray flares by making use
of VLBI and single dish data. Throughout the radio monitoring spanning over two
GeV gamma-ray flares detected by the {\it Fermi}-LAT and the MAGIC Cherenkov
Telescope in the periods of 2009 April to May and 2010 June to August, total
flux density in radio band increases on average. This flux increase mostly
originates in C3. Although the gamma-ray flares span on the timescale of days
to weeks, no clear correlation with the radio light curve on this timescale is
found. Any new prominent components and change in morphology associated with
the gamma-ray flares are not found on the VLBI images.Comment: 6 pages, 3 figures, accepted for publication in MNRAS lette
Carcass characteristics and meat quality of broilers fed on earthworm (Lumbricus rubellus) meal
ÎÎÎ ÎÎÎ΀ÎÎÎ΀ÎÎ Î ÎÎĄÎÎÎΚÎThe aim of the research was to evaluate the carcass characteristics and meat quality from chickens fed on diets in which fish meal was substituted with raw earthworms (Lumbricus rubellus) or earthworm meal. In the trial which lasted 42-days, 100 one-day-old Hybro broilers were divided into the control and three experimental groups. The control group was fed on standard broiler feed, the first (E-I) and the second experimental groups (E-II) were fed a diet in which 50% or 100% of fish meal was substituted with earthworm meal, respectively, whilst the third group (E-III) consumed feed without fish meal, but was given raw chopped earthworms ad libitum from day 1 to day 42. The replacement of fish meal with fresh earthworms resulted in significantly lower carcass weights in the E-III group in comparison with the control group (p<0.05). The differences in drumstick, thigh and breast meat share relative to the carcass mass were not significant (p>0.05). The lowest fat content in thigh and breast meat was in the group in which fish meal was replaced with earthworm meal. The lightness (L*) of thigh and breast meat was highest in the broilers fed fresh earthworms ad libitum. No significant differences in pH value were detected between the experimental groups (p>0.05). The most consumer acceptable were drumstick samples from E-II group and the least acceptable samples from the control group. Earthworm meal may be considered an adequate substitute for fish meal in broiler chickensâ diet since it does not impair the production performance, carcass yield and meat quality
Very-high energy gamma-ray astronomy: A 23-year success story in high-energy astroparticle physics
Very-high energy (VHE) gamma quanta contribute only a minuscule fraction -
below one per million - to the flux of cosmic rays. Nevertheless, being neutral
particles they are currently the best "messengers" of processes from the
relativistic/ultra-relativistic Universe because they can be extrapolated back
to their origin. The window of VHE gamma rays was opened only in 1989 by the
Whipple collaboration, reporting the observation of TeV gamma rays from the
Crab nebula. After a slow start, this new field of research is now rapidly
expanding with the discovery of more than 150 VHE gamma-ray emitting sources.
Progress is intimately related with the steady improvement of detectors and
rapidly increasing computing power. We give an overview of the early attempts
before and around 1989 and the progress after the pioneering work of the
Whipple collaboration. The main focus of this article is on the development of
experimental techniques for Earth-bound gamma-ray detectors; consequently, more
emphasis is given to those experiments that made an initial breakthrough rather
than to the successors which often had and have a similar (sometimes even
higher) scientific output as the pioneering experiments. The considered energy
threshold is about 30 GeV. At lower energies, observations can presently only
be performed with balloon or satellite-borne detectors. Irrespective of the
stormy experimental progress, the success story could not have been called a
success story without a broad scientific output. Therefore we conclude this
article with a summary of the scientific rationales and main results achieved
over the last two decades.Comment: 45 pages, 38 figures, review prepared for EPJ-H special issue "Cosmic
rays, gamma rays and neutrinos: A survey of 100 years of research
Effects of the toluene and methanol extract of Senna (Cassia angustifolia Vahl) on viability and proliferation HeLa cells
Senna (Cassia angustifolia Vahl.) is used in food and pharmaceutical technologies as officinal drugs and natural laxative. The aim of the study was to investigate the effect of toluene and methanol Senna extracts on the viability and proliferation of HeLa cells. The senna leaves were extracted in Soxhlet's extractor and obtained toluene and methanolic extracts were used for determination of effects on viability and proliferation. Cytotoxic effect of different concentrations (0.1%, 0.01%, 0.001% and 0.0001%) extracts was investigated in HeLa cells in vitro. MTT test showed significant cytotoxic activity for toluene extract, especially the concentration of 0.1%, while the tested concentrations metanolic extract did not show cytotoxic activity
Don't bleach chaotic data
A common first step in time series signal analysis involves digitally
filtering the data to remove linear correlations. The residual data is
spectrally white (it is ``bleached''), but in principle retains the nonlinear
structure of the original time series. It is well known that simple linear
autocorrelation can give rise to spurious results in algorithms for estimating
nonlinear invariants, such as fractal dimension and Lyapunov exponents. In
theory, bleached data avoids these pitfalls. But in practice, bleaching
obscures the underlying deterministic structure of a low-dimensional chaotic
process. This appears to be a property of the chaos itself, since nonchaotic
data are not similarly affected. The adverse effects of bleaching are
demonstrated in a series of numerical experiments on known chaotic data. Some
theoretical aspects are also discussed.Comment: 12 dense pages (82K) of ordinary LaTeX; uses macro psfig.tex for
inclusion of figures in text; figures are uufile'd into a single file of size
306K; the final dvips'd postscript file is about 1.3mb Replaced 9/30/93 to
incorporate final changes in the proofs and to make the LaTeX more portable;
the paper will appear in CHAOS 4 (Dec, 1993
On leptonic models for blazars in the Fermi era
Some questions raised by Fermi-LAT data about blazars are summarized, along
with attempts at solutions within the context of leptonic models. These include
both spectral and statistical questions, including the origin of the GeV breaks
in low-synchrotron peaked blazars, the location of the gamma-ray emission
sites, the correlations in the spectral energy distributions with luminosity,
and the difficulty of synchrotron/SSC models to fit the spectra of some TeV
blazars.Comment: 9 pages, 1 figure, in "Beamed and Unbeamed Gamma Rays from Galaxies,"
Muonio, Finland, 11-15 April, 2011, ed. R. Wagner, L. Maraschi, A. Sillanpaa,
to appear in Journal of Physics: Conference Serie
Detection of branon dark matter with gamma ray telescopes
Branons are new degrees of freedom that appear in flexible brane-world models
corresponding to brane fluctuations. These new fields can behave as standard
weakly interacting massive particles (WIMPs) with a significant associated
thermal relic density. We analyze the present constraints from their
spontaneous annihilations into photons for EGRET, Fermi-LAT and MAGIC, and the
prospects for detection in future Cherenkov telescopes. In particular, we focus
on possible signals coming from the Galactic Center and different dwarf
spheroidals, such as Draco, Sagittarius, Canis Major and SEGUE 1. We conclude
that for those targets, present observations are below the sensitivity limits
for branon detection by assuming standard dark matter distributions and no
additional boost factors. However, future experiments such as CTA could be able
to detect gamma-ray photons coming from the annihilation of branons with masses
higher than 150 GeV.Comment: 10 pages, 3 figure
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