Foreground removal for Square Kilometre Array observations of the Epoch of Reionization with the Correlated Component Analysis

We apply the Correlated Component Analysis (CCA) method on simulated data of the Square Kilometre Array, with the aim of accurately cleaning the 21 cm reionization signal from diffuse foreground contamination. The CCA has been developed for the Cosmic Microwave Background, but the application of the Fourier-domain implementation of this method to the reionization signal is straightforward. The CCA is a parametric method to estimate the frequency behaviour of the foregrounds from the data by using second-order statistics. We test its performance on foreground simulations of increasing complexity, designed to challenge the parametric models adopted. We also drop the assumption of spectral smoothness that most of the methods rely upon. We are able to clean effectively the simulated data across the explored frequency range (100-200 MHz) for all the foreground simulations. This shows that the CCA method is very promising for EoR component separation.Comment: 12 pages, 15 figures, accepted by MNRA

A new model of the microwave polarized sky for CMB experiments

We present a new model of the microwave sky in polarization that can be used to simulate data from CMB polarization experiments. We exploit the most recent results from the Planck satellite to provide an accurate description of the diffuse polarized foreground synchrotron and thermal dust emission. Our model can include the two mentioned foregrounds, and also a constructed template of Anomalous Microwave Emission (AME). Several options for the frequency dependence of the foregrounds can be easily selected, to reflect our uncertainties and to test the impact of different assumptions. Small angular scale features can be added to the foreground templates to simulate high-resolution observations. We present tests of the model outputs to show the excellent agreement with Planck and WMAP data. We determine the range within which the foreground spectral indices can be varied to be consistent with the current data. We also show forecasts for a high-sensitivity, high-resolution full-sky experiment such as the Cosmic ORigin Explorer (COrE). Our model is released as a python script that is quick and easy to use, available at \url{http://www.jb.man.ac.uk/~chervias}.Comment: 12 pages, 14 Figures, 1 Table, Accepted by MNRA

SKA Weak Lensing III: Added Value of Multi-Wavelength Synergies for the Mitigation of Systematics

In this third paper of a series on radio weak lensing for cosmology with the Square Kilometre Array, we scrutinise synergies between cosmic shear measurements in the radio and optical/near-IR bands for mitigating systematic effects. We focus on three main classes of systematics: (i) experimental systematic errors in the observed shear; (ii) signal contamination by intrinsic alignments; and (iii) systematic effects due to an incorrect modelling of non-linear scales. First, we show that a comprehensive, multi-wavelength analysis provides a self-calibration method for experimental systematic effects, only implying <50% increment on the errors on cosmological parameters. We also illustrate how the cross-correlation between radio and optical/near-IR surveys alone is able to remove residual systematics with variance as large as 0.00001, i.e. the same order of magnitude of the cosmological signal. This also opens the possibility of using such a cross-correlation as a means to detect unknown experimental systematics. Secondly, we demonstrate that, thanks to polarisation information, radio weak lensing surveys will be able to mitigate contamination by intrinsic alignments, in a way similar but fully complementary to available self-calibration methods based on position-shear correlations. Lastly, we illustrate how radio weak lensing experiments, reaching higher redshifts than those accessible to optical surveys, will probe dark energy and the growth of cosmic structures in regimes less contaminated by non-linearities in the matter perturbations. For instance, the higher-redshift bins of radio catalogues peak at z~0.8-1, whereas their optical/near-IR counterparts are limited to z<0.5-0.7. This translates into having a cosmological signal 2 to 5 times less contaminated by non-linear perturbations.Comment: 16 pages, 10 figures, 2 tables; improved discussion of experimental systematics in Sec. 2; updated to match published versio

SKA Weak Lensing II: Simulated Performance and Survey Design Considerations

We construct a pipeline for simulating weak lensing cosmology surveys with the Square Kilometre Array (SKA), taking as inputs telescope sensitivity curves; correlated source flux, size and redshift distributions; a simple ionospheric model; source redshift and ellipticity measurement errors. We then use this simulation pipeline to optimise a 2-year weak lensing survey performed with the first deployment of the SKA (SKA1). Our assessments are based on the total signal-to-noise of the recovered shear power spectra, a metric that we find to correlate very well with a standard dark energy figure of merit. We first consider the choice of frequency band, trading off increases in number counts at lower frequencies against poorer resolution; our analysis strongly prefers the higher frequency Band 2 (950-1760 MHz) channel of the SKA-MID telescope to the lower frequency Band 1 (350-1050 MHz). Best results would be obtained by allowing the centre of Band 2 to shift towards lower frequency, around 1.1 GHz. We then move on to consider survey size, finding that an area of 5,000 square degrees is optimal for most SKA1 instrumental configurations. Finally, we forecast the performance of a weak lensing survey with the second deployment of the SKA. The increased survey size (3$\pi$\,steradian) and sensitivity improves both the signal-to-noise and the dark energy metrics by two orders of magnitude.Comment: 15 pages, 11 figures, 1 table. Comments welcome. Updated to match published versio

Thurstonian Scaling of Compositional Questionnaire Data

To prevent response biases, personality questionnaires may use comparative response formats. These include forced choice, where respondents choose among a number of items, and quantitative comparisons, where respondents indicate the extent to which items are preferred to each other. The present article extends Thurstonian modeling of binary choice data (Brown & Maydeu-Olivares, 2011a) to “proportion-of-total” (compositional) formats. Following Aitchison (1982), compositional item data are transformed into log-ratios, conceptualized as differences of latent item utilities. The mean and covariance structure of the log-ratios is modelled using Confirmatory Factor Analysis (CFA), where the item utilities are first-order factors, and personal attributes measured by a questionnaire are second-order factors. A simulation study with two sample sizes, N=300 and N=1000, shows that the method provides very good recovery of true parameters and near-nominal rejection rates. The approach is illustrated with empirical data from N=317 students, comparing model parameters obtained with compositional and Likert scale versions of a Big Five measure. The results show that the proposed model successfully captures the latent structures and person scores on the measured traits

Species-specific differences in the expression of the HNF1A, HNF1B and HNF4A genes

addresses: Institute of Biomedical and Clinical Sciences, Peninsula Medical School, University of Exeter, Exeter, United Kingdom. [email protected]: PMCID: PMC2773013types: Journal Article; Research Support, Non-U.S. Gov'tCopyright: © 2009 Harries et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The HNF1A, HNF1B and HNF4A genes are part of an autoregulatory network in mammalian pancreas, liver, kidney and gut. The layout of this network appears to be similar in rodents and humans, but inactivation of HNF1A, HNF1B or HNF4A genes in animal models cause divergent phenotypes to those seen in man. We hypothesised that some differences may arise from variation in the expression profile of alternatively processed isoforms between species

Influence of Context on Item Parameters in Forced-Choice Personality Assessments

A fundamental assumption in computerized adaptive testing (CAT) is that item parameters are invariant with respect to context – items surrounding the administered item. This assumption, however, may not hold in forced-choice (FC) assessments, where explicit comparisons are made between items included in the same block. We empirically examined the influence of context on item parameters by comparing parameter estimates from two FC instruments. The first instrument was compiled of blocks of three items, whereas in the second, the context was manipulated by adding one item to each block, resulting in blocks of four. The item parameter estimates were highly similar. However, a small number of significant deviations were observed, confirming the importance of context when designing adaptive FC assessments. Two patterns of such deviations were identified, and methods to reduce their occurrences in a FC CAT setting were proposed. It was shown that with a small proportion of violations of the parameter invariance assumption, score estimation remained stable

The Tiered Radio Extragalactic Continuum Simulation (T-RECS)

We present the Tiered Radio Extragalactic Continuum Simulation (T-RECS): a new simulation of the radio sky in continuum, over the 150 MHz-20 GHz range. T-RECS models two main populations of radio galaxies: Active Galactic Nuclei (AGNs) and Star-Forming Galaxies (SFGs), and corresponding sub-populations. Our model also includes polarized emission over the full frequency range, which has been characterised statistically for each population using the available information. We model the clustering properties in terms of probability distributions of hosting halo masses, and use lightcones extracted from a high-resolution cosmological simulation to determine the positions of haloes. This limits the sky area for the simulations including clustering to a 25deg2 field of view. We compare luminosity functions, number counts in total intensity and polarization, and clustering properties of our outputs to up-to-date compilations of data and find a very good agreement. We deliver a set of simulated catalogues, as well as the code to produce them, which can be used for simulating observations and predicting results from deep radio surveys with existing and forthcoming radio facilities, such as the Square Kilometre Array (SKA).Comment: 20 pages, 11 figures, accepted by MNRA

Bismuth-Based Nano- and Microparticles in X-Ray Contrast, Radiation Therapy, and Radiation Shielding Applications

Bismuth has gained attention in preclinical research because of its ability to attenuate X-rays and high biocompatibility, which make it an excellent element for use in a biomedical agent or in radiation shielding. Developments in the synthesis of elemental bismuth nano- and microparticles, their X-radiation interactions, and their biological interactions will be reviewed in this chapter. The chapter will pay special focus to emerging medical applications of elemental bismuth nano- and microparticles, including the possibility of targeted molecular X-ray imaging, photo-thermal and X-radiation dose enhancing therapies for cancer treatment, and the construction of flexible radiation shielding materials and X-ray opaque devices

How water limits influence conservation in Massachusetts towns

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2006.Includes bibliographical references (p. 54-58).It's surprising to learn that the water-rich state of Massachusetts experiences incidences of water stress, where rivers go dry for stretches of the year and where municipalities struggle to meet water demand. Water conservation and demand management is one important part of reducing pressures on water supplies and alleviating ecosystem stress. Although the state has recently revisited water management policies and has promoted revised measures to increase conservation, the actual measures taken are implemented on the scale of the municipality. This thesis examines three affluent suburban municipalities located in stressed river basins in eastern Massachusetts that have taken different degrees of conservation and demand management efforts. The stories reveal that the decisions to curb water demand have been influenced by the degree to which towns have experienced a perceptible limit to their supply. These towns also show us how a crisis, or an event of water shortage, can bring focus to the limits of water, providing an opportunity for town managers to redefine the problem in such a way that conservation is the solution.(cont.) As towns continue to face increasing pressure on water supplies, some municipalities would like to turn to regional water. Although these regional systems can help offset some ecological pressures as well as promote economy of scales, it raises questions as to whether such a system would remove the perceptible limit that gives impetus for conservation.by Anna L. Brown.M.C.P