1,207 research outputs found
New insights into foreground analysis of the WMAP five-year data using FASTICA
In this paper, we present a foreground analysis of the WMAP 5-year data using
the FASTICA algorithm, improving on the treatment of the WMAP 3-year data in
Bottino et al 2008. We revisit the nature of the free-free spectrum with the
emphasis on attempting to confirm or otherwise the spectral feature claimed in
Dobbler et al 2008b and explained in terms of spinning dust emission in the
warm ionised medium. With the application of different Galactic cuts, the index
is always flatter than the canonical value of 2.14 except for the Kp0 mask
which is steeper. Irrespective of this, we can not confirm the presence of any
feature in the free-free spectrum. We experiment with a more extensive approach
to the cleaning of the data, introduced in connection with the iterative
application of FASTICA. We confirm the presence of a residual foreground whose
spatial distribution is concentrated along the Galactic plane, with pronounced
emission near the Galactic center. This is consistent with the WMAP haze
detected in Finkbeiner 2004. Finally, we attempted to perform the same analysis
on full-sky maps. The code returns good results even for those regions where
the cross-talk among the components is high. However, slightly better results
in terms of the possibility of reconstructing a full-sky CMB map, are achieved
with a simultaneous analysis of both the five WMAP maps and foreground
templates. Nonetheless, some residuals are still present and detected in terms
of an excess in the CMB power spectrum, on small angular scales. Therefore, a
minimal mask for the brightest regions of the plane is necessary, and has been
defined.Comment: Accepted for publication in MNRAS, 25 pages, 17 figures, 4 tables.
Version with full resolution figures available at:
http://www.mpa-garching.mpg.de/~bottino/downloads/bottino_etal.pd
Prospects For Detecting Dark Matter With GLAST In Light Of The WMAP Haze
Observations by the WMAP experiment have identified an excess of microwave
emission from the center of the Milky Way. It has previously been shown that
this "WMAP Haze" could be synchrotron emission from relativistic electrons and
positrons produced in the annihilations of dark matter particles. In
particular, the intensity, spectrum and angular distribution of the WMAP Haze
is consistent with an electroweak scale dark matter particle (such as a
supersymmetric neutralino or Kaluza-Klein dark matter in models with universal
extra dimensions) annihilating with a cross section on the order of sigma
v~3x10^-26 cm^3/s and distributed with a cusped halo profile. No further exotic
astrophysical or annihilation boost factors are required. If dark matter
annihilations are in fact responsible for the observed Haze, then other
annihilation products will also be produced, including gamma rays. In this
article, we study the prospects for the GLAST satellite to detect gamma rays
from dark matter annihilations in the Galactic Center region in this scenario.
We find that by studying only the inner 0.1 degrees around the Galactic Center,
GLAST will be able to detect dark matter annihilating to heavy quarks or gauge
bosons over astrophysical backgrounds with 5sigma (3sigma) significance if they
are lighter than approximately 320-500 GeV (500-750 GeV). If the angular window
is broadened to study the dark matter halo profile's angular extension (while
simultaneously reducing the astrophysical backgrounds), WIMPs as heavy as
several TeV can be identified by GLAST with high significance. Only if the dark
matter particles annihilate mostly to electrons or muons will GLAST be unable
to identify the gamma ray spectrum associated with the WMAP Haze.Comment: 10 pages, 6 figure
Indoor Navigation with MEMS sensors
AbstractAccurate positioning becomes extremely important for modern application like indoor navigation and location-based services. Standalone GPS cannot meet this accuracy. In this paper a method to couple GPS and a high resolution MEMS pressure sensor is presented to improve vertical as well as horizontal (in urban canyon environment) positioning. Further, a step counter based on an accelerometer is improved with an altimeter for stair detection and automatic step length adaptation for dead reckoning inside buildings. Finally, a stand-alone system accurately tracks floor levels inside buildings, using only a pressure sensor
Cosmic Ray Accelerators in the Large Magellanic Cloud
I point out a correlation between gamma-ray emissivity and the historical
star formation rate in the Large Magellanic Cloud ~12.5 Myr ago. This
correlation bolsters the view that CRs in the LMC are accelerated by
conglomerations of supernova remnants: i.e. superbubbles and supergiant shells.Comment: Research Not
Inference via Wild Bootstrap and Multiple Imputation under Fine-Gray Models with Incomplete Data
Fine-Gray models specify the subdistribution hazards for one out of multiple
competing risks to be proportional. The estimators of parameters and cumulative
incidence functions under Fine-Gray models have a simpler structure when data
are censoring-complete than when they are more generally incomplete. This paper
considers the case of incomplete data but it exploits the above-mentioned
simpler estimator structure for which there exists a wild bootstrap approach
for inferential purposes. The present idea is to link the methodology under
censoring-completeness with the more general right-censoring regime with the
help of multiple imputation. In a simulation study, this approach is compared
to the estimation procedure proposed in the original paper by Fine and Gray
when it is combined with a bootstrap approach. An application to a data set
about hospital-acquired infections illustrates the method.Comment: 32 pages, 2 figures, 1 tabl
High‐resolution monthly precipitation climatologies over Norway (1981–2010): Joining numerical model data sets and in situ observations
The 1981-2010 monthly precipitation climatologies for Norway at 1 km resolution are presented. They are computed by an interpolation procedure (HCLIM+RK) combining the output from a numerical model with the in situ observations. Specifically, the regional climate model data set HCLIM-AROME, based on the dynamical downscaling of the global ERA-Interim reanalysis onto 2.5 km resolution, is considered together with 2009 rain-gauges located within the model domain. The precipitation climatologies are defined by superimposing the grid of 1981-2010 monthly normals from the numerical model and the kriging interpolation of station residuals. The combined approach aims at improving the quality of gridded climatologies and at providing reliable precipitation gradients also over those remote Norwegian regions not covered by observations, especially over the northernmost mountainous areas. The integration of rain-gauge data greatly reduces the original HCLIM-AROME biases. The HCLIM+RK errors obtained from the leave-one-out station validation turn out to be lower than those provided by two considered interpolation schemes based on observations only: a multi-linear local regression kriging (MLRK) and a local weighted linear regression (LWLR). As average over all months, the mean absolute (percentage) error is 10.0 mm (11%) for HCLIM+RK, and 11.4 (12%) and 11.6 mm (12%) for MLRK and LWLR, respectively. In addition, by comparing the results at both station and grid cell level, the accuracy of MLRK and LWLR is more sensitive to the spatial variability of station distribution over the domain and their interpolated fields are more affected by discontinuities and outliers, especially over those areas not covered by the rain-gauge network. The obtained HCLIM+RK climatologies clearly depict the main west-to-east gradient occurring from the orographic precipitation regime of the coast to the more continental climate of the inland and it allows to point out the features of the climatic subzones of Norway
Wild Bootstrap for Counting Process-Based Statistics
The wild bootstrap is a popular resampling method in the context of
time-to-event data analyses. Previous works established the large sample
properties of it for applications to different estimators and test statistics.
It can be used to justify the accuracy of inference procedures such as
hypothesis tests or time-simultaneous confidence bands. This paper consists of
two parts: in Part~I, a general framework is developed in which the large
sample properties are established in a unified way by using martingale
structures. The framework includes most of the well-known non- and
semiparametric statistical methods in time-to-event analysis and parametric
approaches. In Part II, the Fine-Gray proportional sub-hazards model
exemplifies the theory for inference on cumulative incidence functions given
the covariates. The model falls within the framework if the data are
censoring-complete. A simulation study demonstrates the reliability of the
method and an application to a data set about hospital-acquired infections
illustrates the statistical procedure.Comment: 2 parts, 115 pages, 2 figures, 13 table
Analysis of WMAP 7-year Temperature Data: Astrophysics of the Galactic Haze
We analyse WMAP 7-year temperature data, jointly modeling the cosmic
microwave background (CMB) and Galactic foreground emission. We use the
Commander code based on Gibbs sampling. Thus, from the WMAP7 data, we derive
simultaneously the CMB and Galactic components on scales larger than 1deg with
sensitivity improved relative to previous work. We conduct a detailed study of
the low-frequency foreground with particular focus on the "microwave haze"
emission around the Galactic center. We demonstrate improved performance in
quantifying the diffuse galactic emission when Haslam 408MHz data are included
together with WMAP7, and the spinning and thermal dust emission is modeled
jointly. We also address the question of whether the hypothetical galactic haze
can be explained by a spatial variation of the synchrotron spectral index. The
excess of emission around the Galactic center appears stable with respect to
variations of the foreground model that we study. Our results demonstrate that
the new galactic foreground component - the microwave haze - is indeed present.Comment: 16 pages, 16 figures, Published on Ap
Linac Twins in Radiotherapy
In a radiotherapy department having more than one linear accelerator, it is rather common to match the dose output of all machines. In particular, the recently developed flattening filter free mode requires new investigations regarding the feasibility of matching and the consequences for quality assurance and workload. This refers also to the beam model of the radiotherapy treatment planning system. Our results show that matching is possible not only for flat beams but also for flattening filter free mode. Therefore, the machines can substitute each other in the case of breakdown or service without new treatment planning even in the case of complex intensity-modulated radiotherapy or volumetric-modulated arc therapy. The quality assurance is reduced to only one data set for both the linear accelerators and the radiotherapy treatment planning system
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