704 research outputs found
Bayesian DNA copy number analysis
BACKGROUND: Some diseases, like tumors, can be related to chromosomal aberrations, leading to
changes of DNA copy number. The copy number of an aberrant genome can be represented as a
piecewise constant function, since it can exhibit regions of deletions or gains. Instead, in a healthy
cell the copy number is two because we inherit one copy of each chromosome from each our
parents.
Bayesian Piecewise Constant Regression (BPCR) is a Bayesian regression method for data that are
noisy observations of a piecewise constant function. The method estimates the unknown segment
number, the endpoints of the segments and the value of the segment levels of the underlying
piecewise constant function. The Bayesian Regression Curve (BRC) estimates the same data with
a smoothing curve. However, in the original formulation, some estimators failed to properly
determine the corresponding parameters. For example, the boundary estimator did not take into
account the dependency among the boundaries and succeeded in estimating more than one
breakpoint at the same position, losing segments.
RESULTS: We derived an improved version of the BPCR (called mBPCR) and BRC, changing the
segment number estimator and the boundary estimator to enhance the fitting procedure. We also
proposed an alternative estimator of the variance of the segment levels, which is useful in case of
data with high noise. Using artificial data, we compared the original and the modified version of
BPCR and BRC with other regression methods, showing that our improved version of BPCR
generally outperformed all the others. Similar results were also observed on real data.
CONCLUSION: We propose an improved method for DNA copy number estimation, mBPCR, which
performed very well compared to previously published algorithms. In particular, mBPCR was more
powerful in the detection of the true position of the breakpoints and of small aberrations in very
noisy data. Hence, from a biological point of view, our method can be very useful, for example, to
find targets of genomic aberrations in clinical cancer samples
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
HelMod in the works: from direct observations to the local interstellar spectrum of cosmic-ray electrons
The local interstellar spectrum (LIS) of cosmic-ray (CR) electrons for the
energy range 1 MeV to 1 TeV is derived using the most recent experimental
results combined with the state-of-the-art models for CR propagation in the
Galaxy and in the heliosphere. Two propagation packages, GALPROP and HelMod,
are combined to provide a single framework that is run to reproduce direct
measurements of CR species at different modulation levels, and at both
polarities of the solar magnetic field. An iterative maximum-likelihood method
is developed that uses GALPROP-predicted LIS as input to HelMod, which provides
the modulated spectra for specific time periods of the selected experiments for
model-data comparison. The optimized HelMod parameters are then used to adjust
GALPROP parameters to predict a refined LIS with the procedure repeated subject
to a convergence criterion. The parameter optimization uses an extensive data
set of proton spectra from 1997-2015. The proposed CR electron LIS accommodates
both the low-energy interstellar spectra measured by Voyager 1 as well as the
high-energy observations by PAMELA and AMS-02 that are made deep in the
heliosphere; it also accounts for Ulysses counting rate features measured out
of the ecliptic plane. The interstellar and heliospheric propagation parameters
derived in this study agree well with our earlier results for CR protons,
helium nuclei, and anti-protons propagation and LIS obtained in the same
framework.Comment: 11 pages, 14 figures, 4 tables; ApJ, in pres
Deciphering the local Interstellar spectra of primary cosmic ray species with HelMod
Local interstellar spectra (LIS) of primary cosmic ray (CR) nuclei, such as
helium, oxygen, and mostly primary carbon are derived for the rigidity range
from 10 MV to ~200 TV using the most recent experimental results combined with
the state-of-the-art models for CR propagation in the Galaxy and in the
heliosphere. Two propagation packages, GALPROP and HelMod, are combined into a
single framework that is used to reproduce direct measurements of CR species at
different modulation levels, and at both polarities of the solar magnetic
field. The developed iterative maximum-likelihood method uses GALPROP-predicted
LIS as input to HelMod, which provides the modulated spectra for specific time
periods of the selected experiments for model-data comparison. The interstellar
and heliospheric propagation parameters derived in this study are consistent
with our prior analyses using the same methodology for propagation of CR
protons, helium, antiprotons, and electrons. The resulting LIS accommodate a
variety of measurements made in the local interstellar space (Voyager 1) and
deep inside the heliosphere at low (ACE/CRIS, HEAO-3) and high energies
(PAMELA, AMS-02).Comment: 13 pages, 13 figures, 6 tables, ApJ in press. arXiv admin note: text
overlap with arXiv:1704.0633
Life expectancy of young adults with follicular lymphoma
FL patients younger than 40 have a median OS of 24 years and their outcome improved over time. However, they still have a significantly shorter life expectancy when compared with that of an age-matched general healthy population. FL in young adults, differently from paediatric FL, does not seem to represent a distinct entit
Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP
Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are
used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~
events. Spin correlations are favoured by data, and found to agree with the
Standard Model predictions. In addition, correlations between the W-boson decay
planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events.
Decay-plane correlations, consistent with zero and with the Standard Model
predictions, are measured
Ultrarelativistic sources in nonlinear electrodynamics
The fields of rapidly moving sources are studied within nonlinear
electrodynamics by boosting the fields of sources at rest. As a consequence of
the ultrarelativistic limit the delta-like electromagnetic shock waves are
found. The character of the field within the shock depends on the theory of
nonlinear electrodynamics considered. In particular, we obtain the field of an
ultrarelativistic charge in the Born-Infeld theory.Comment: 10 pages, 3 figure
Measurement of the Cross Section for Open-Beauty Production in Photon-Photon Collisions at LEP
The cross section for open-beauty production in photon-photon collisions is
measured using the whole high-energy and high-luminosity data sample collected
by the L3 detector at LEP. This corresponds to 627/pb of integrated luminosity
for electron-positron centre-of-mass energies from 189GeV to 209GeV. Events
containing b quarks are identified through their semi-leptonic decay into
electrons or muons. The e+e- -> e+e-b b~X cross section is measured within our
fiducial volume and then extrapolated to the full phase space. These results
are found to be in significant excess with respect to Monte Carlo predictions
and next-to-leading order QCD calculations
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