265 research outputs found
Nuclear and Non-Ionizing Energy-Loss for Coulomb Scattered Particles from Low Energy up to Relativistic Regime in Space Radiation Environment
In the space environment, instruments onboard of spacecrafts can be affected
by displacement damage due to radiation. The differential scattering cross
section for screened nucleus--nucleus interactions - i.e., including the
effects due to screened Coulomb nuclear fields -, nuclear stopping powers and
non-ionization energy losses are treated from about 50 keV/nucleon up to
relativistic energies.Comment: Accepted for publication in the Proceedings of the ICATPP Conference
on Cosmic Rays for Particle and Astroparticle Physics, Villa Olmo (Como,
Italy), 7--8 October, 2010, to be published by World Scientifi
Antiproton modulation in the Heliosphere and AMS-02 antiproton over proton ratio prediction
We implemented a quasi time-dependent 2D stochastic model of solar modulation
describing the transport of cosmic rays (CR) in the heliosphere. Our code can
modulate the Local Interstellar Spectrum (LIS) of a generic charged particle
(light cosmic ions and electrons), calculating the spectrum at 1AU. Several
measurements of CR antiparticles have been performed. Here we focused our
attention on the CR antiproton component and the antiproton over proton ratio.
We show that our model, using the same heliospheric parameters for both
particles, fit the observed anti-p/p ratio. We show a good agreement with
BESS-97 and PAMELA data and make a prediction for the AMS-02 experiment
Electrical Characterization of SiPM as a Function of Test Frequency and Temperature
Silicon Photomultipliers (SiPM) represent a promising alternative to
classical photomultipliers, for instance, for the detection of photons in high
energy physics and medical physics. In the present work, electrical
characterizations of test devices - manufactured by ST Microelectronics - are
presented. SiPMs with an area of 3.5x3.5 micron^2 and a cell pitch of 54 micron
were manufactured as arrays of 64x64 cells and exhibiting a fill factor of 31%.
The capacitance of SiPMs was measured as a function of reverse bias voltage at
frequencies ranging from from 20 Hz up to 1 MHz and temperatures from 300 K
down to 85 K. While leakage currents were measured at temperatures from 400 K
down to 85 K. Thus, the threshold voltage - i.e., voltage corresponding to that
at which the multiplication regime for the leakage current begins - could be
determined as a function of temperature. Finally, an electrical model suited to
reproduce the dependence of the frequency dependence of capacitance is
presented.Comment: To appear on the Proceedings of the 13th ICATPP Conference on
Astroparticle, Particle, Space Physics and Detectors for Physics
Applications, Villa Olmo (Como, Italy), 3-7 October, 2011, to be published by
World Scientific (Singapore
Proton Modulation in the Heliosphere for Different Solar Conditions and Prediction for AMS-02
Spectra of Galactic Cosmic Rays (GCRs) measured at the Earth are the
combination of several processes: sources production and acceleration,
propagation in the interstellar medium and propagation in the heliosphere.
Inside the solar cavity the flux of GCRs is reduced due to the solar
modulation, the interaction which they have with the interplanetary medium. We
realized a 2D stochastic simulation of solar modulation to reproduce CR spectra
at the Earth, and evaluated the importance in our results of the Local
Interstellar Spectrum (LIS) model and its agreement with data at high energy.
We show a good agreement between our model and the data taken by AMS-01 and
BESS experiments during periods with different solar activity conditions.
Furthermore we made a prediction for the flux which will be measured by AMS-02
experiment.Comment: Accepted for publication in the Proceedings of the ICATPP Conference
on Cosmic Rays for Particle and Astroparticle Physics, Villa Olmo (Como,
Italy), 7-8 October, 2010, to be published by World Scientific (Singapore
Latitudinal Dependence of Cosmic Rays Modulation at 1 AU and Interplanetary-Magnetic-Field Polar Correction
The cosmic rays differential intensity inside the heliosphere, for energy
below 30 GeV/nuc, depends on solar activity and interplanetary magnetic field
polarity. This variation, termed solar modulation, is described using a 2-D
(radius and colatitude) Monte Carlo approach for solving the Parker transport
equation that includes diffusion, convection, magnetic drift and adiabatic
energy loss. Since the whole transport is strongly related to the
interplanetary magnetic field (IMF) structure, a better understanding of his
description is needed in order to reproduce the cosmic rays intensity at the
Earth, as well as outside the ecliptic plane. In this work an interplanetary
magnetic field model including the standard description on ecliptic region and
a polar correction is presented. This treatment of the IMF, implemented in the
HelMod Monte Carlo code (version 2.0), was used to determine the effects on the
differential intensity of Proton at 1\,AU and allowed one to investigate how
latitudinal gradients of proton intensities, observed in the inner heliosphere
with the Ulysses spacecraft during 1995, can be affected by the modification of
the IMF in the polar regions.Comment: accepted for publication inAdvances in Astronom
Suprathermal particle addition to solar wind pressure: possible influence on magnetospheric transmissivity of low energy cosmic rays?
Energetic (suprathermal) solar particles, accelerated in the interplanetary
medium, contribute to the solar wind pressure, in particular during high solar
activity periods. We estimated the effect of the increase of solar wind
pressure due to suprathermal particles on magnetospheric transmissivity of
galactic cosmic rays in the case of one recent solar event
The Genome-wide impact of Nipblb loss-of-function on Zebrafish gene expression
Transcriptional changes normally occur during development but also underlie differences between healthy and pathological conditions. Transcription factors or chromatin modifiers are involved in orchestrating gene activity, such as the cohesin genes and their regulator NIPBL. In our previous studies, using a zebrafish model for nipblb knockdown, we described the effect of nipblb loss-of-function in specific contexts, such as central nervous system development and hematopoiesis. However, the genome-wide transcriptional impact of nipblb loss-of-function in zebrafish embryos at diverse developmental stages remains under investigation. By RNA-seq analyses in zebrafish embryos at 24 h post-fertilization, we examined genome-wide effects of nipblb knockdown on transcriptional programs. Differential gene expression analysis revealed that nipblb loss-of-function has an impact on gene expression at 24 h post fertilization, mainly resulting in gene inactivation. A similar transcriptional effect has also been reported in other organisms, supporting the use of zebrafish as a model to understand the role of Nipbl in gene regulation during early vertebrate development. Moreover, we unraveled a connection between nipblb-dependent differential expression and gene expression patterns of hematological cell populations and AML subtypes, enforcing our previous evidence on the involvement of NIPBL-related transcriptional dysregulation in hematological malignancies
Gut resistome plasticity in pediatric patients undergoing hematopoietic stem cell transplantation
The gut microbiome of pediatric patients undergoing allo-hematopoietic stem cell transplantation (HSCT) has recently been considered as a potential reservoir of antimicrobial resistance, with important implications in terms of patient mortality rate. By means of shotgun metagenomics, here we explored the dynamics of the gut resistome \u2013 i.e. the pattern of antibiotic resistance genes provided by the gut microbiome \u2013 in eight pediatric patients undergoing HSCT, half of whom developed acute Graft-versus-Host Disease (aGvHD). According to our findings, the patients developing aGvHD are characterized by post-HSCT expansion of their gut resistome, involving the acquisition of new resistances, as well as the consolidation of those already present before HSCT. Interestingly, the aGvHD-associated bloom in resistome diversity is not limited to genes coding for resistance to the antibiotics administered along the therapeutic course, but rather involves a broad pattern of different resistance classes, including multidrug resistance, as well as resistance to macrolides, aminoglycosides, tetracyclines and beta-lactams. Our data stress the relevance of mapping the gut resistome in HSCT pediatric patients to define the most appropriate anti-infective treatment post HSCT
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