1,081 research outputs found
El pensamiento finalista como obståculo epistemológico para la enseñanza del modelo darwiniano
En este trabajo presentamos evidencias que apoyan la hipĂłtesis segĂșn la cual el pensamiento finalista funciona como un obstĂĄculo para el aprendizaje del modelo darwiniano. Estas evidencias provienen de la indagaciĂłn de las concepciones de los estudiantes, la puesta en prĂĄctica de una unidad didĂĄctica centrada en la superaciĂłn de este obstĂĄculo y el anĂĄlisis epistemolĂłgico del modelo cientĂfico
Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b - First data from the GIARPS Commissioning
Context. Stellar activity is currently challenging the detection of young
planets via the radial velocity (RV) technique. Aims. We attempt to
definitively discriminate the nature of the RV variations for the young active
K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent
results on the existence of a substellar companion. Methods. We compare VIS
data with high precision RVs in the near infrared (NIR) range by using the
GIANO - B and IGRINS spectrographs. In addition, we present for the first time
simultaneous VIS-NIR observations obtained with GIARPS (GIANO - B and HARPS -
N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV
amplitude does not change at different wavelengths, while stellar activity
induces wavelength-dependent RV variations, which are significantly reduced in
the NIR range with respect to the VIS. Results. The NIR radial velocity
measurements from GIANO - B and IGRINS show an average amplitude of about one
quarter with respect to previously published VIS data, as expected when the RV
jitter is due to stellar activity. Coeval multi-band photometry surprisingly
shows larger amplitudes in the NIR range, explainable with a mixture of cool
and hot spots in the same active region. Conclusions. In this work, the claimed
massive planet around BD+20 1790 is ruled out by our data. We exploited the
crucial role of multi- wavelength spectroscopy when observing young active
stars: thanks to facilities like GIARPS that provide simultaneous observations,
this method can reach its maximum potential.Comment: 12 pages, 7 figure
Multiwavelength observations of 3C 454.3 II. The AGILE 2007 December campaign
We report on the second AGILE multiwavelength campaign of the blazar 3C 454.3
during the first half of December 2007. This campaign involved AGILE, Spitzer,
Swift,Suzaku,the WEBT consortium,the REM and MITSuME telescopes,offering a
broad band coverage that allowed for a simultaneous sampling of the synchrotron
and inverse Compton (IC) emissions.The 2-week AGILE monitoring was accompanied
by radio to optical monitoring by WEBT and REM and by sparse observations in
mid-Infrared and soft/hard X-ray energy bands performed by means of Target of
Opportunity observations by Spitzer, Swift and Suzaku, respectively.The source
was detected with an average flux of~250x10^{-8}ph cm^-2s^-1 above 100
MeV,typical of its flaring states.The simultaneous optical and gamma-ray
monitoring allowed us to study the time-lag associated with the variability in
the two energy bands, resulting in a possible ~1-day delay of the gamma-ray
emission with respect to the optical one. From the simultaneous optical and
gamma-ray fast flare detected on December 12, we can constrain the delay
between the gamma-ray and optical emissions within 12 hours. Moreover, we
obtain three Spectral Energy Distributions (SEDs) with simultaneous data for
2007 December 5, 13, 15, characterized by the widest multifrequency coverage.
We found that a model with an external Compton on seed photons by a standard
disk and reprocessed by the Broad Line Regions does not describe in a
satisfactory way the SEDs of 2007 December 5, 13 and 15. An additional
contribution, possibly from the hot corona with T=10^6 K surrounding the jet,
is required to account simultaneously for the softness of the synchrotron and
the hardness of the inverse Compton emissions during those epochs.Comment: 13 pages, 8 figures, 2 tables, Accepted for publication in Ap
Planck 2015 results. XXIII. The thermal Sunyaev-Zeldovich effect--cosmic infrared background correlation
We use Planck data to detect the cross-correlation between the thermal
Sunyaev-Zeldovich (tSZ) effect and the infrared emission from the galaxies that
make up the the cosmic infrared background (CIB). We first perform a stacking
analysis towards Planck-confirmed galaxy clusters. We detect infrared emission
produced by dusty galaxies inside these clusters and demonstrate that the
infrared emission is about 50% more extended than the tSZ effect. Modelling the
emission with a Navarro--Frenk--White profile, we find that the radial profile
concentration parameter is . This indicates
that infrared galaxies in the outskirts of clusters have higher infrared flux
than cluster-core galaxies. We also study the cross-correlation between tSZ and
CIB anisotropies, following three alternative approaches based on power
spectrum analyses: (i) using a catalogue of confirmed clusters detected in
Planck data; (ii) using an all-sky tSZ map built from Planck frequency maps;
and (iii) using cross-spectra between Planck frequency maps. With the three
different methods, we detect the tSZ-CIB cross-power spectrum at significance
levels of (i) 6 , (ii) 3 , and (iii) 4 . We model the
tSZ-CIB cross-correlation signature and compare predictions with the
measurements. The amplitude of the cross-correlation relative to the fiducial
model is . This result is consistent with
predictions for the tSZ-CIB cross-correlation assuming the best-fit
cosmological model from Planck 2015 results along with the tSZ and CIB scaling
relations.Comment: 18 pages, 16 figure
Definitions, Criteria and Global Classification of Mast Cell Disorders with Special Reference to Mast Cell Activation Syndromes: A Consensus Proposal
Activation of tissue mast cells (MCs) and their abnormal growth and accumulation in various organs are typically found in primary MC disorders also referred to as mastocytosis. However, increasing numbers of patients are now being informed that their clinical findings are due to MC activation (MCA) that is neither associated with mastocytosis nor with a defined allergic or inflammatory reaction. In other patients with MCA, MCs appear to be clonal cells, but criteria for diagnosing mastocytosis are not met. A working conference was organized in 2010 with the aim to define criteria for diagnosing MCA and related disorders, and to propose a global unifying classification of all MC disorders and pathologic MC reactions. This classification includes three types of `MCA syndromes' (MCASs), namely primary MCAS, secondary MCAS and idiopathic MCAS. MCA is now defined by robust and generally applicable criteria, including (1) typical clinical symptoms, (2) a substantial transient increase in serum total tryptase level or an increase in other MC-derived mediators, such as histamine or prostaglandin D 2, or their urinary metabolites, and (3) a response of clinical symptoms to agents that attenuate the production or activities of MC mediators. These criteria should assist in the identification and diagnosis of patients with MCAS, and in avoiding misdiagnoses or overinterpretation of clinical symptoms in daily practice. Moreover, the MCAS concept should stimulate research in order to identify and exploit new molecular mechanisms and therapeutic targets. Copyright (C) 2011 S. Karger AG, Base
CD4 recovery following antiretroviral treatment interruptions in children and adolescents with HIV infection in Europe and Thailand
OBJECTIVES: The aim of the study was to explore factors associated with CD4 percentage (CD4%) reconstitution following treatment interruptions (TIs) of antiretroviral therapy (ART). METHODS: Data from paediatric HIVâinfected cohorts across 17 countries in Europe and Thailand were pooled. Children on combination ART (cART; at least three drugs from at least two classes) for > 6 months before TI of â„ 30 days while aged < 18 years were included. CD4% at restart of ART (râART) and in the long term (up to 24 months after râART) following the first TI was modelled using asymptotic regression. RESULTS: In 779 children with at least one TI, the median age at first TI was 10.1 [interquartile range (IQR) 6.4, 13.6] years and the mean CD4% was 27.3% [standard deviation (SD) 11.0%]; the median TI duration was 9.0 (IQR 3.5, 22.5) months. In regression analysis, the mean CD4% was 19.2% [95% confidence interval (CI) 18.3, 20.1%] at râART, and 27.1% (26.2, 27.9%) in the long term, with half this increase in the first 6 months. râART and longâterm CD4% values were highest in female patients and in children aged < 3 years at the start of TI. Longâterm CD4% was highest in those with a TI lasting 1 to <3 months, those with râART after year 2000 and those with a CD4% nadir â„ 25% (all P < 0.001). The effect of CD4% nadir during the TI differed significantly (P = 0.038) by viral suppression at the start of the TI; in children with CD4% nadir < 15% during TI, recovery was better in those virally suppressed prior to the TI; viral suppression was not associated with recovery in children with CD4% nadir â„ 25%. CONCLUSIONS: After restart of ART following TI, most children reconstituted well immunologically. Nevertheless, several factors predicted better immunological reconstitution, including younger age and higher nadir CD4% during TI
Planck intermediate results: XVI. Profile likelihoods for cosmological parameters
We explore the 2013 Planck likelihood function with a high-precision multi-dimensional minimizer (Minuit). This allows a refinement of the ÎCDM best-fit solution with respect to previously-released results, and the construction of frequentist confidence intervals using profile likelihoods. The agreement with the cosmological results from the Bayesian framework is excellent, demonstrating the robustness of the Planck results to the statistical methodology. We investigate the inclusion of neutrino masses, where more significant differences may appear due to the non-Gaussian nature of the posterior mass distribution. By applying the Feldman-Cousins prescription, we again obtain results very similar to those of the Bayesian methodology. However, the profile-likelihood analysis of the cosmic microwave background (CMB) combination (Planck+WP+highL) reveals a minimum well within the unphysical negative-mass region. We show that inclusion of the Planck CMB-lensing information regularizes this issue, and provide a robust frequentist upper limit â mÎœ †0.26 eV (95% confidence) from the CMB+lensing+BAO data combination.
Reproduced with permission from Astronomy & Astrophysics, © ESO 201
Planck intermediate results XXIV : Constraints on variations in fundamental constants
Any variation in the fundamental physical constants, more particularly in the fine structure constant, a, or in the mass of the electron, me, affects the recombination history of the Universe and cause an imprint on the cosmic microwave background angular power spectra. We show that the Planck data allow one to improve the constraint on the time variation of the fine structure constant at redshift z - 10(3) by about a factor of 5 compared to WMAP data, as well as to break the degeneracy with the Hubble constant, H-0. In addition to a, we can set a constraint on the variation in the mass of the electron, me, and in the simultaneous variation of the two constants. We examine in detail the degeneracies between fundamental constants and the cosmological parameters, in order to compare the limits obtained from Planck and WMAP and to determine the constraining power gained by including other cosmological probes. We conclude that independent time variations of the fine structure constant and of the mass of the electron are constrained by Planck to Delta alpha/alpha = (3.6 +/- 3.7) x 10(-3) and Delta m(e)/m(e) = (4 +/- 11) x 10(-3) at the 68% confidence level. We also investigate the possibility of a spatial variation of the fine structure constant. The relative amplitude of a dipolar spatial variation in a (corresponding to a gradient across our Hubble volume) is constrained to be delta alpha/alpha = (-2.4 +/- 3.7) x 10(-2).Peer reviewe
Planck intermediate results. XLVI. Reduction of large-scale systematic effects in HFI polarization maps and estimation of the reionization optical depth
This paper describes the identification, modelling, and removal of previously unexplained systematic effects in the polarization data of the Planck High Frequency Instrument (HFI) on large angular scales, including new mapmaking and calibration procedures, new and more complete end-to-end simulations, and a set of robust internal consistency checks on the resulting maps. These maps, at 100, 143, 217, and 353âGHz, are early versions of those that will be released in final form later in 2016. The improvements allow us to determine the cosmic reionization optical depth Ï using, for the first time, the low-multipole EE data from HFI, reducing significantly the central value and uncertainty, and hence the upper limit. Two different likelihood procedures are used to constrain Ï from two estimators of the CMB E- and B-mode angular power spectra at 100 and 143âGHz, after debiasing the spectra from a small remaining systematic contamination. These all give fully consistent results. A further consistency test is performed using cross-correlations derived from the Low Frequency Instrument maps of the Planck 2015 data release and the new HFI data. For this purpose, end-to-end analyses of systematic effects from the two instruments are used to demonstrate the near independence of their dominant systematic error residuals. The tightest result comes from the HFI-based Ï posterior distribution using the maximum likelihood power spectrum estimator from EE data only, giving a value 0.055 ± 0.009. In a companion paper these results are discussed in the context of the best-fit PlanckÎCDM cosmological model and recent models of reionization
Planck intermediate results. L. Evidence of spatial variation of the polarized thermal dust spectral energy distribution and implications for CMB B-mode analysis
The characterization of the Galactic foregrounds has been shown to be the main obstacle in thechallenging quest to detect primordial B-modes in the polarized microwave sky. We make use of the Planck-HFI 2015 data release at high frequencies to place new constraints on the properties of the polarized thermal dust emission at high Galactic latitudes. Here, we specifically study the spatial variability of the dust polarized spectral energy distribution (SED), and its potential impact on the determination of the tensor-to-scalar ratio, r. We use the correlation ratio of the CBBâ angular power spectra between the 217 and 353âGHz channels as a tracer of these potential variations, computed on different high Galactic latitude regions, ranging from 80% to 20% of the sky. The new insight from Planck data is a departure of the correlation ratio from unity that cannot be attributed to a spurious decorrelation due to the cosmic microwave background, instrumental noise, or instrumental systematics. The effect is marginally detected on each region, but the statistical combination of all the regions gives more than 99% confidence for this variation in polarized dust properties. In addition, we show that the decorrelation increases when there is a decrease in the mean column density of the region of the sky being considered, and we propose a simple power-law empirical model for this dependence, which matches what is seen in the Planck data. We explore the effect that this measured decorrelation has on simulations of the BICEP2-Keck Array/Planck analysis and show that the 2015 constraints from these data still allow a decorrelation between the dust at 150 and 353âGHz that is compatible with our measured value. Finally, using simplified models, we show that either spatial variation of the dust SED or of the dust polarization angle are able to produce decorrelations between 217 and 353âGHz data similar to the values we observe in the data
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