96 research outputs found
Antimatter research in Space
Two of the most compelling issues facing astrophysics and cosmology today are
to understand the nature of the dark matter that pervades the universe and to
understand the apparent absence of cosmological antimatter. For both issues,
sensitive measurements of cosmic-ray antiprotons and positrons, in a wide
energy range, are crucial. Many different mechanisms can contribute to
antiprotons and positrons production, ranging from conventional reactions up to
exotic processes like neutralino annihilation. The open problems are so
fundamental (i.e.: is the universe symmetric in matter and antimatter ?) that
experiments in this field will probably be of the greatest interest in the next
years. Here we will summarize the present situation, showing the different
hypothesis and models and the experimental measurements needed to lead to a
more established scenario.Comment: 10 pages, 7 figures, Invited talk at the 18th European Cosmic Ray
Symposium, Moscow, July 2002, submitted to Journal of Physics
Diffractive Interaction and Scaling Violation in pp->pi^0 Interaction and GeV Excess in Galactic Diffuse Gamma-Ray Spectrum of EGRET
We present here a new calculation of the gamma-ray spectrum from pp->pi^0 in
the Galactic ridge environment. The calculation includes the diffractive pp
interaction and incorporates the Feynman scaling violation for the first time.
Galactic diffuse gamma-rays come, predominantly, from pi^0->gamma gamma in the
sub-GeV to multi-GeV range. Hunter et al. found, however, an excess in the GeV
range ("GeV Excess") in the EGRET Galactic diffuse spectrum above the
prediction based on experimental pp->pi^0 cross-sections and the Feynman
scaling hypothesis. We show, in this work, that the diffractive process makes
the gamma-ray spectrum harder than the incident proton spectrum by ~0.05 in
power-law index, and, that the scaling violation produces 30-80% more pi^0 than
the scaling model for incident proton energies above 100GeV. Combination of the
two can explain about a half of the "GeV Excess" with the local cosmic proton
(power-law index ~2.7). The excess can be fully explained if the proton
spectral index in the Galactic ridge is a little harder (~0.2 in power-law
index) than the local spectrum. Given also in the paper is that the diffractive
process enhances e^+ over e^- and the scaling violation gives 50-100% higher
p-bar yield than without the violation, both in the multi-GeV range.Comment: 35 pages, 11 figures, to appear in Astrophysical Journa
Deriving the mass of particles from Extended Theories of Gravity in LHC era
We derive a geometrical approach to produce the mass of particles that could
be suitably tested at LHC. Starting from a 5D unification scheme, we show that
all the known interactions could be suitably deduced as an induced symmetry
breaking of the non-unitary GL(4)-group of diffeomorphisms. The deformations
inducing such a breaking act as vector bosons that, depending on the
gravitational mass states, can assume the role of interaction bosons like
gluons, electroweak bosons or photon. The further gravitational degrees of
freedom, emerging from the reduction mechanism in 4D, eliminate the hierarchy
problem since generate a cut-off comparable with electroweak one at TeV scales.
In this "economic" scheme, gravity should induce the other interactions in a
non-perturbative way.Comment: 30 pages, 1 figur
On inconsistency of experimental data on primary nuclei spectra with sea level muon intensity measurements
For the first time a complete set of the most recent direct data on primary
cosmic ray spectra is used as input into calculations of muon flux at sea level
in wide energy range GeV. Computations have been performed
with the CORSIKA/QGSJET and CORSIKA/VENUS codes. The comparison of the obtained
muon intensity with the data of muon experiments shows, that measurements of
primary nuclei spectra conform to sea level muon data only up to several tens
of GeV and result in essential deficit of muons at higher energies. As it
follows from our examination, uncertainties in muon flux measurements and in
the description of nuclear cascades development are not suitable to explain
this contradiction, and the only remaining factor, leading to this situation,
is underestimation of primary light nuclei fluxes. We have considered
systematic effects, that may distort the results of the primary cosmic ray
measurements with the application of the emulsion chambers. We suggest, that
re-examination of these measurements is required with the employment of
different hadronic interaction models. Also, in our point of view, it is
necessary to perform estimates of possible influence of the fact, that sizable
fraction of events, identified as protons, actually are antiprotons. Study of
these cosmic ray component begins to attract much attention, but today nothing
definite is known for the energies GeV. In any case, to realize whether
the mentioned, or some other reasons are the sources of disagreement of the
data on primaries with the data on muons, the indicated effects should be
thoroughly analyzed
Balloon Measurements of Cosmic Ray Muon Spectra in the Atmosphere along with those of Primary Protons and Helium Nuclei over Mid-Latitude
We report here the measurements of the energy spectra of atmospheric muons
and of the cosmic ray primary proton and helium nuclei in a single experiment.
These were carried out using the MASS superconducting spectrometer in a balloon
flight experiment in 1991. The relevance of these results to the atmospheric
neutrino anomaly is emphasized. In particular, this approach allows
uncertainties caused by the level of solar modulation, the geomagnetic cut-off
of the primaries and possible experimental systematics to be decoupled in the
comparison of calculated fluxes of muons to measured muon fluxes. The muon
observations cover the momentum and depth ranges of 0.3-40 GeV/c and 5-886
g/cmsquared, respectively. The proton and helium primary measurements cover the
rigidity range from 3 to 100 GV, in which both the solar modulation and the
geomagnetic cut-off affect the energy spectra at low energies.Comment: 31 pages, including 17 figures, simplified apparatus figure, to
appear in Phys. Rev.
The Cosmic-Ray antiproton flux between 3 and 49 GeV
We report on a new measurement of the cosmic ray antiproton spectrum. The
data were collected by the balloon-borne experiment CAPRICE98 which was flown
on 28-29 May 1998 from Fort Sumner, New Mexico, USA. The experiment used the
NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas
Ring Imaging Cherenkov (RICH) detector, a time-of-flight system, a tracking
device consisting of drift chambers and a superconducting magnet and a
silicon-tungsten calorimeter. The RICH detector was the first ever flown
capable of mass-resolving charge-one particles at energies above 5 GeV.
A total of 31 antiprotons with rigidities between 4 and 50 GV at the
spectrometer were identified with small backgrounds from other particles. The
absolute antiproton energy spectrum was determined in the kinetic energy region
at the top of the atmosphere between 3.2 and 49.1 GeV. We found that the
observed antiproton spectrum and the antiproton-to-proton ratio are consistent
with a pure secondary origin. However, a primary component may not be excluded.Comment: 39 pages, 11 Postscript figures, uses AAS LATEX style; changes in
sections 3.1.1, 3.3, 3.4 and 6, Figure 8 modified, 2 figures added, typos
correcte
Comparison of Atmospheric Neutrino Flux Calculations at Low Energies
We compare several different calculations of the atmospheric neutrino flux in
the energy range relevant for contained neutrino interactions, and we identify
the major sources of difference among the calculations. We find nothing that
would affect the predicted ratio of , which is nearly the same
in all calculations. Significant differences in normalization arise primarily
from different treatment of pion production by interactions of protons in the
atmosphere. Different assumptions about the primary spectrum and treatment of
the geomagnetic field are also of some importance.Comment: 15 pages, RevTeX , 5 postscript figures, submitted to Phys. Rev.
Uncertainties of Cosmic Ray Spectra and Detectability of Antiproton mSUGRA Contributions With PAMELA
We studied the variation of and top of the atmosphere spectra
due to the parameters uncertainties of the Milky Way geometry, propagation
models and cross sections. We used the B/C data and Galprop code for the
propagation analysis. We also derived the uncertainty bands for subFe/Fe ratio,
H and He. Finally, we considered a neutralino induced component in the
antiproton flux in the mSUGRA framework. PAMELA expectations for positrons and
antiprotons are calculated. We studied in details the possibility of
disentanglement of an eventual signal component in the antiproton spectra in a
clumpy halo scenario: minimal values of clumpiness factors necessary to
disentangle the signal from the background without violating the quality of the
antiproton data fit are found. There are also given examples of total spectra
in comparison with existing experimental data and an example of PAMELA
prediction for the total spectra. The main result of this work is that for the
diffusion and convection background model PAMELA will be able to disentangle an
eventual supersymmetric signal even for small clumpiness factors.Comment: 26 pages, 27 eps figures. Final JCAP accepted versio
Portuguese propolis disturbs glycolytic metabolism of human colorectal cancer in vitro
Propolis is a resin collected by bees from plant buds and exudates, which is further processed through the activity of bee enzymes. Propolis has been shown to possess many biological and pharmacological properties, such as antimicrobial, antioxidant, immunostimulant and antitumor activities. Due to this bioactivity profile, this resin can become an alternative, economic and safe source of natural bioactive compounds.Antitumor action has been reported in vitro and in vivo for propolis extracts or its isolated compounds; however, Portuguese propolis has been little explored. The aim of this work was to evaluate the in vitro antitumor activity of Portuguese propolis on the human colon carcinoma cell line HCT-15, assessing the effect of different fractions (hexane, chloroform and ethanol residual) of a propolis ethanol extract on cell viability, proliferation, metabolism and death.
METHODS:
Propolis from Angra do Heroísmo (Azores) was extracted with ethanol and sequentially fractionated in solvents with increasing polarity, n-hexane and chloroform. To assess cell viability, cell proliferation and cell death, Sulforhodamine B, BrDU incorporation assay and Anexin V/Propidium iodide were used, respectively. Glycolytic metabolism was estimated using specific kits.
RESULTS:
All propolis samples exhibited a cytotoxic effect against tumor cells, in a dose- and time-dependent way. Chloroform fraction, the most enriched in phenolic compounds, appears to be the most active, both in terms of inhibition of viability and cell death. Data also show that this cytotoxicity involves disturbance in tumor cell glycolytic metabolism, seen by a decrease in glucose consumption and lactate production.
CONCLUSION:
Our results show that Portuguese propolis from Angra do Heroísmo (Azores) can be a potential therapeutic agent against human colorectal cancer.We thank the Portuguese Science and Technology Foundation (FCT) for VMG fellowship (ref. SFRH/BI/33503/2008). The authors thank Mr. Antonio Marques from Frutercoop - Azores, who kindly collected and provided the propolis sample for the study
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