202 research outputs found
Biparametric Adaptive Filter: detection of compact sources in complex microwave backgrounds
In this article we consider the detection of compact sources in maps of the
Cosmic Microwave Background radiation (CMB) following the philosophy behind the
Mexican Hat Wavelet Family (MHWn) of linear filters. We present a new
analytical filter, the Biparametric Adaptive Filter (BAF), that is able to
adapt itself to the statistical properties of the background as well as to the
profile of the compact sources, maximizing the amplification and improving the
detection process. We have tested the performance of this filter using
realistic simulations of the microwave sky between 30 and 857 GHz as observed
by the Planck satellite, where complex backgrounds can be found. We demonstrate
that doing a local analysis on flat patches allows one to find a combination of
the optimal scale of the filter R and the index of the filter g that will
produce a global maximum in the amplification, enhancing the signal-to-noise
ratio (SNR) of the detected sources in the filtered map and improving the total
number of detections above a threshold. We conclude that the new filter is able
to improve the overall performance of the MHW2, increasing the SNR of the
detections and, therefore, the number of detections above a 5 sigma threshold.
The improvement of the new filter in terms of SNR is particularly important in
the vicinity of the galactic plane and in the presence of strong galactic
emission. Finally, we compare the sources detected by each method and find that
the new filter is able to detect more new sources than the MHW2 at all
frequencies and in clean regions of the sky. The BAF is also less affected by
spurious detections, associated to compact structures in the vicinity of the
galactic plane.Comment: 17 pages, 15 figures and 3 tables. Accepted for publication in MNRA
Detection/estimation of the modulus of a vector. Application to point source detection in polarization data
Given a set of images, whose pixel values can be considered as the components
of a vector, it is interesting to estimate the modulus of such a vector in some
localised areas corresponding to a compact signal. For instance, the
detection/estimation of a polarized signal in compact sources immersed in a
background is relevant in some fields like astrophysics. We develop two
different techniques, one based on the Neyman-Pearson lemma, the Neyman-Pearson
filter (NPF), and another based on prefiltering-before-fusion, the filtered
fusion (FF), to deal with the problem of detection of the source and estimation
of the polarization given two or three images corresponding to the different
components of polarization (two for linear polarization, three including
circular polarization). For the case of linear polarization, we have performed
numerical simulations on two-dimensional patches to test these filters
following two different approaches (a blind and a non-blind detection),
considering extragalactic point sources immersed in cosmic microwave background
(CMB) and non-stationary noise with the conditions of the 70 GHz \emph{Planck}
channel. The FF outperforms the NPF, especially for low fluxes. We can detect
with the FF extragalactic sources in a high noise zone with fluxes >=
(0.42,0.36) Jy for (blind/non-blind) detection and in a low noise zone with
fluxes >= (0.22,0.18) Jy for (blind/non-blind) detection with low errors in the
estimated flux and position.Comment: 11 pages, 5 figure
Extragalactic Compact Sources in the Planck Sky and Their Cosmological Implications
The Planck satellite has proved to be a very successful mission, which has
been operating flawlessly for more than 36 months. Its main purpose is to map
the anisotropies of the CMB radiation at 9 frequencies, between 30 and 857 GHz,
with unprecedented resolution and sensitivity. After a description of the
properties and cosmological aims of Planck, we review the results obtained
during the first 1.6 full sky surveys relative to compact extragalactic sources
and their implications. The most recent and efficient methods and filters for
compact source detection in the presence of Gaussian noise and CMB anisotropies
are discussed. The first surveys of Planck have enabled the detection of about
200 galaxy clusters, by the SZ effect, and from several hundreds to many
thousands of extragalactic point sources (EPS), presented in the Planck ERCSC.
We review the results on the SZ effect in galaxy clusters. We discuss the
possibilities of future Planck data to study clusters through the SZ effect and
the interesting possibilities of combining these data with X ray observations.
These EPS can be classified into two main source classes: radio sources, at
intermediate to high z; far IR sources, typically at very z. Planck number
counts of EPS at LFI frequencies are in agreement with WMAP counts. A clear
steepening of the mean spectral index of bright radio sources is observed above
70 GHz, that can be interpreted in terms of a break frequency in their spectra.
For nearby dusty galaxies, Planck observations find evidence of colder dust,
with T < 20 K, than has previously been found. More recently, the number counts
of bright local dusty galaxies and of synchrotron sources have been measured by
Planck at submm wavelengths. Planck has provided interesting results on the
angular distribution of CIB anisotropies, allowing us to put new constraints on
clustering properties of dusty galaxies at high z.Comment: 30 pages, 12 figures. Abstract absent in the published version. See
http://www.intechopen.com/articles/show/title/extragalactic-compact-sources-in-the-planck-sky-and-their-cosmological-implication
Targeted Disruption of Core 1 β1,3-galactosyltransferase (C1galt1) Induces Apical Endocytic Trafficking in Human Corneal Keratinocytes
Exposed mucosal surfaces limit constitutive endocytosis under physiological conditions to prevent uptake of macromolecules and pathogens and, therefore, cellular damage. It is now accepted that cell surface mucins, a group of high molecular weight glycoproteins on the epithelial glycocalyx, defined by their extensive O-glycosylation, play a major role in maintaining barrier function in these surfaces, but the precise mechanisms are unclear.In this work, we utilized a stable tetracycline-inducible RNA interfering system targeting the core 1 ß1,3-galactosyltransferase (C1galt1 or T-synthase), a critical galactosyltransferase required for the synthesis of core 1 O-glycans, to explore the role of mucin-type carbohydrates in apical endocytic trafficking in human corneal keratinocytes. Using cell surface biotinylation and subcellular fractionation, we found increased accumulation of plasma membrane protein in endosomes after C1galt1 depletion. Confocal laser scanning microscopy and fluorometry revealed increased translocation of negatively charged fluorescent nanospheres after C1galt1 knockdown sustained by an active transport process and largely independent of apical intercellular junctions. Internalization of nanospheres could be blocked by dynasore, nocodazole, chlorpromazine, and hyperosmotic sucrose, suggesting a mechanism for clathrin-coated pit budding and vesicular trafficking. This possibility was supported by experiments showing nanosphere colocalization with clathrin heavy chain in the cytoplasm.Together, the data suggest that core 1 O-glycans contribute to maintenance of apical barrier function on exposed mucosal surfaces by preventing clathrin-mediated endocytosis
A Bayesian method for point source polarization estimation
The estimation of the polarization of extragalactic compact sources in
Cosmic Microwave Background images is a very important task in order to clean
these images for cosmological purposes -- as, for example, to constrain the
tensor-to-scalar ratio of primordial fluctuations during inflation -- and also
to obtain relevant astrophysical information about the compact sources
themselves in a frequency range, -- GHz, where observations
have only very recently started to be available. In this paper we propose a
Bayesian maximum a posteriori (MAP) approach estimation scheme which
incorporates prior information about the distribution of the polarization
fraction of extragalactic compact sources between 1 and 100 GHz. We apply this
Bayesian scheme to white noise simulations and to more realistic simulations
that include CMB intensity, Galactic foregrounds and instrumental noise with
the characteristics of the QUIJOTE experiment Wide Survey at 11 GHz. Using
these simulations, we also compare our Bayesian method with the frequentist
Filtered Fusion method that has been already used in WMAP data and in the
\emph{Planck} mission. We find that the Bayesian method allows us to decrease
the threshold for a feasible estimation of to levels below mJy
(as compared to mJy that was the equivalent threshold for the
frequentist Filtered Fusion). We compare the bias introduced by the Bayesian
method and find it to be small in absolute terms. Finally, we test the
robustness of the Bayesian estimator against uncertainties in the prior and in
the flux density of the sources. We find that the Bayesian estimator is robust
against moderate changes in the parameters of the prior and almost insensitive
to realistic errors in the estimated photometry of the sources.Comment: 15 pages, 12 figures, submitted to A&
Pressure-Induced Phase-Transition Sequence In Cof 2 : An Experimental And First-Principles Study On The Crystal, Vibrational, And Electronic Properties
We report a complete structural study of CoF2 under pressure. Its crystal structure and vibrational and electronic properties have been studied both theoretically and experimentally using first-principles density functional theory (DFT) methods, x-ray diffraction, x-ray absorption at Co K-edge experiments, Raman spectroscopy, and optical absorption in the 0–80 GPa range. We have determined the structural phase-transition sequence in CoF2 and corresponding transition pressures. The results are similar to other transition-metal difluorides such as FeF2 but different to ZnF2 and MgF2, despite that the Co2+ size (ionic radius) is similar to Zn2+ and Mg2+. We found that the complete phase-transition sequence is tetragonal rutile (P42/mnm) → CaCl2 type (orthorhombic Pnnm) → distorted PdF2 (orthorhombic Pbca)+PdF2 (cubic Pa3¯) in coexistence → fluorite (cubic Fm3¯m) → cotunnite (orthorhombic Pnma). It was observed that the structural phase transition to the fluorite at 15 GPa involves a drastic change of coordination from sixfold octahedral to eightfold cubic with important modifications in the vibrational and electronic properties. We show that the stabilization of this high-pressure cubic phase is possible under nonhydrostatic conditions since ideal hydrostaticity would stabilize the distorted-fluorite structure (tetragonal I4/mmm) instead. Although the first rutile → CaCl2-type second-order phase transition is subtle by Raman spectroscopy, it was possible to define it through the broadening of the Eg Raman mode which is split in the CaCl2-type phase. First-principles DFT calculations are in fair agreement with the experimental Raman mode frequencies, thus providing an accurate description for all vibrational modes and elastic properties of CoF2 as a function of pressure
Caracterización simbiótica y filogenética de rizobios que nodulan la nueva especie Lupinus mariae-josephi
Una nueva especie de altramuz, Lupinus mariae-josephi, ha sido identificado recientemente en Valencia (Pascual, H.). Esta especie, a diferencia de las descritas en la Península ibérica y en el viejo mundo, no crece en suelos ácidos sino en suelos alcalinos y con alto contenido en calcio. El objetivo general de este proyecto es investigar si existen diferencias fenotípicas y genéticas entre los rizobios que nodulan Lupinus mariae-josephi y lupinos de suelos ácidos nativos de la Península Ibérica (Lupinus angustifolius, L.luteus y otras cuatro especies). En este proyecto se han aislado bacterias (rizobios) de nódulos de L. maria-josephi a partir de suelos básicos de Valencia (localidad de LLombai) y se está realizando su caracterización a nivel morfológico, nutricional, simbiótico y molecular. A nivel molecular se han comparado los genes “housekeeping” 16S rRNA, recA, atpD, gln2 y el simbiótico, nodC de diversas cepas que nodulan L. mariae-josephi y con cepas de otras especies de rizobios. Por otra parte, también se está evaluando la capacidad de L. mariae-josephi de ser nodulada por diferentes rizobios bajo condiciones bacteriológicamente controladas
IS CONTRAST-ASSOCIATED ACUTE KIDNEY INJURY (CA-AKI) ASSOCIATED TO THE TYPE OF HOSPITAL AND ICU? PRELIMINAY RESULTS OF THE NEFROCON STUDY
Polarization of the WMAP Point Sources
The detection of polarized sources in the WMAP 5-year data is a very
difficult task. The maps are dominated by instrumental noise and only a handful
of sources show up as clear peaks in the Q and U maps. Optimal linear filters
applied at the position of known bright sources detect with a high level of
significance a polarized flux P from many more sources, but estimates of P are
liable to biases. Using a new technique, named the "filtered fusion technique",
we have detected in polarization, with a significance level greater than 99.99%
in at least one WMAP channel, 22 objects, 5 of which, however, do not have a
plausible low radio frequency counterpart and are therefore doubtful. Estimated
polarized fluxes P < 400 mJy at 23 GHz were found to be severely affected by
the Eddington bias. The corresponding polarized flux limit for Planck/LFI at 30
GHz, obtained via realistic simulations, is 300 mJy. We have also obtained
statistical estimates of, or upper limits to the mean polarization degrees of
bright WMAP sources at 23, 33, 41, and 61 GHz, finding that they are of a few
percent.Comment: 10 pages, 6 figures. Accepted for publication in Ap
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