First CMB Constraints on Direction-Dependent Cosmological Birefringence from WMAP-7

A Chern-Simons coupling of a new scalar field to electromagnetism may give rise to cosmological birefringence, a rotation of the linear polarization of electromagnetic waves as they propagate over cosmological distances. Prior work has sought this rotation, assuming the rotation angle to be uniform across the sky, by looking for the parity-violating TB and EB correlations a uniform rotation produces in the CMB temperature/polarization. However, if the scalar field that gives rise to cosmological birefringence has spatial fluctuations, then the rotation angle may vary across the sky. Here we search for direction-dependent cosmological birefringence in the WMAP-7 data. We report the first CMB constraint on the rotation-angle power spectrum for multipoles between L = 0 and L = 512. We also obtain a 68% confidence-level upper limit of 1 degree on the square root of the quadrupole of a scale-invariant rotation-angle power spectrum.Comment: 14 pages, 12 figures, 4 tables; accepted to PR

"Changing ourselves, changing others" : an analysis of the life stories of participants in a training course for volunteers within a non-governmental organisation in the Eastern Cape Province of South Africa

Gender-based violence has been recognized as a pressing mental health problem that is prevalent within South African society. Non-governmental organizations play a major role in addressing and highlighting the issue. These organizations make use of volunteers in order to assist in meeting their goals. The modernist perspective has been the dominant investigative mode when research into volunteers has been conducted. However, this study has been conducted with an emphasis on narrative. In its use of this constitutionalist and deconstructive perspective, it examines the identity of the research participants within the dominant social and cultural discourses that story their lives. This presents a major challenge to the modernist framework. In examining the life stories of the participants an emergent nature of identity is noted. Through the process of storying their lives and ascribing meaning to their experiences and understandings, the participants engaged in a process of constructing their identity. This research recognizes that identity is both multi-sited and multi-storied. The emphasis on personal agency enables the participants to restory their lives in the light of challenging prevailing discourses. It is in this process of challenge that they reauthor their lives and are in a position to change their own lives and the lives of others

On the complementarity of galaxy clustering with cosmic shear and flux magnification

In this paper, we motivate the use of galaxy clustering measurements using photometric redshift information, including a contribution from flux magnification, as a probe of cosmology. We present cosmological forecasts when clustering data alone is used, and when clustering is combined with a cosmic shear analysis. We consider two types of clustering analysis: firstly, clustering with only redshift auto-correlations in tomographic redshift bins; secondly, using all available redshift bin correlations. Finally, we consider how inferred cosmological parameters may be biased using each analysis when flux magnification is neglected. Results are presented for a Stage III ground-based survey, and a Stage IV space-based survey modelled with photometric redshift errors, and values for the slope of the luminosity function inferred from CFHTLenS catalogues. We find that combining clustering information with shear can improve constraints on cosmological parameters, giving an improvement to a Dark Energy Task Force-like figure of merit by a factor of 1.33 when only auto-correlations in redshift are used for the clustering analysis, rising to 1.52 when cross-correlations in redshift are also included. The addition of galaxy-galaxy lensing gives further improvement, with increases in figure of merit by a factor of 2.82 and 3.7 for each type of clustering analysis respectively. The presence of flux magnification in a clustering analysis does not significantly affect the precision of cosmological constraints when combined with cosmic shear and galaxy-galaxy lensing. However if magnification is neglected, inferred cosmological parameter values are biased, with biases in some cosmological parameters larger than statistical errors. (Abridged)Comment: Accepted by MNRAS, 18 pages, 12 Figures, 3 Table

Delensing CMB Polarization with External Datasets

One of the primary scientific targets of current and future CMB polarization experiments is the search for a stochastic background of gravity waves in the early universe. As instrumental sensitivity improves, the limiting factor will eventually be B-mode power generated by gravitational lensing, which can be removed through use of so-called delensing algorithms. We forecast prospects for delensing using lensing maps which are obtained externally to CMB polarization: either from large-scale structure observations, or from high-resolution maps of CMB temperature. We conclude that the forecasts in either case are not encouraging, and that significantly delensing large-scale CMB polarization requires high-resolution polarization maps with sufficient sensitivity to measure the lensing B-mode. We also present a simple formalism for including delensing in CMB forecasts which is computationally fast and agrees well with Monte Carlos.Comment: typos correcte

Numerical Stability of Lanczos Methods

The Lanczos algorithm for matrix tridiagonalisation suffers from strong numerical instability in finite precision arithmetic when applied to evaluate matrix eigenvalues. The mechanism by which this instability arises is well documented in the literature. A recent application of the Lanczos algorithm proposed by Bai, Fahey and Golub allows quadrature evaluation of inner products of the form $\psi^\dagger g(A) \psi$. We show that this quadrature evaluation is numerically stable and explain how the numerical errors which are such a fundamental element of the finite precision Lanczos tridiagonalisation procedure are automatically and exactly compensated in the Bai, Fahey and Golub algorithm. In the process, we shed new light on the mechanism by which roundoff error corrupts the Lanczos procedureComment: 3 pages, Lattice 99 contributio

Segmenting root systems in X-ray computed tomography images using level sets

The segmentation of plant roots from soil and other growing media in X-ray computed tomography images is needed to effectively study the root system architecture without excavation. However, segmentation is a challenging problem in this context because the root and non-root regions share similar features. In this paper, we describe a method based on level sets and specifically adapted for this segmentation problem. In particular, we deal with the issues of using a level sets approach on large image volumes for root segmentation, and track active regions of the front using an occupancy grid. This method allows for straightforward modifications to a narrow-band algorithm such that excessive forward and backward movements of the front can be avoided, distance map computations in a narrow band context can be done in linear time through modification of Meijster et al.'s distance transform algorithm, and regions of the image volume are iteratively used to estimate distributions for root versus non-root classes. Results are shown of three plant species of different maturity levels, grown in three different media. Our method compares favorably to a state-of-the-art method for root segmentation in X-ray CT image volumes.Comment: 11 page

Conservation and allocation of slope in gravity sanitary sewer design

Title from PDF of title page (University of Missouri--Columbia, viewed on March 28, 2011).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Thesis advisor: Dr. Kathleen M. Trauth.M.S. University of Missouri--Columbia 2010.Gravity sanitary sewers are traditionally designed in a relatively direct route from source to destination after considering property boundary/easement constraints and topographic features. A methodology is presented in this research for considering potential energy (as measured by elevation and slope) as a resource to be conserved and deliberately allocated in gravity sanitary sewer routing. A graphical tool was first developed for identifying acceptable design flow limits for a gravity sanitary sewer based on hydraulic and practical constraints. A GIS map that incorporates a DEM can be used to obtain elevation information for a selected study area. Baseline and alternative slope-conserving sewer routes can then be selected by considering the pixel-to-pixel elevation change of the DEM and the acceptable design flow illustrated in the graphical tool. The baseline and alternative slope-conserving routes can be compared by calculating the total trenched volume required to maintain gravity flow within design constraints throughout each route. The methodology was tested in an undeveloped area near Ashland, Missouri to simulate a new development. Two pairs of baseline and slope conserving routes were evaluated, and the slope-conserving routes were found to require less trenched volume than the baseline routes despite being longer.Includes bibliographical references

Regional differences in store-operated Ca2+ entry in the epithelium of the intact human lens

An elevated level of Ca2+ is an important factor in cataract, yet precisely how Ca2+ enters the lens is unknown. Lens epithelial cells contain a range of G-protein–coupled receptors and receptor tyrosine kinases that induce increases in intracellular Ca2+. Receptor-associated Ca2+ influx is, therefore, likely to be an important route for Ca2+ influx to the lens. The authors investigated stimulated and passive Ca2+ influx in in situ human lens epithelium. Ca2+ changes in equatorial (E) and central anterior (CA) epithelial cells were monitored with the use of a Ca2+ indicator (Fluo4) and confocal microscopy. Gene expression was monitored by RT-PCR and immunoblotting. Adenosine triphosphate (ATP) induced Ca2+ responses that were smaller in CA than E. Ca2+ store depletion, using ATP (100 µM) or thapsigargin (1 µM), revealed greater relative store capacity and Ca2+ influx in E. Ca2+ influx was blocked by La3+ (0.5 µM) in both regions. Unstimulated Ca2+ influx was greater in E than CA. Greater expression of Orai1 and STIM1 was detected in E than in CA. Greater Ca2+ store capacity and Ca2+ influx in E compared with CA reflects underlying differences in proliferation and differentiation between the regions. The relatively small resting Ca2+ influx in CA epithelium suggests that store-operated Ca2+ entry (SOCE) is the main route of Ca2+ influx in these cells. Greater resting influx and SOCE in E cells suggests that these are a major route for Ca2+ influx into the lens. Increased expression of Orai1 and STIM1 in E could account for the differences in Ca2+ entry. Receptor activation will modulate Ca2+ influx, and inappropriate activity may contribute to cortical cataract

A new transgenic reporter line reveals Wnt-dependent Snai2 re-expression and cranial neural crest differentiation in Xenopus

During vertebrate embryogenesis, the cranial neural crest (CNC) forms at the neural plate border and subsequently migrates and differentiates into many types of cells. The transcription factor Snai2, which is induced by canonical Wnt signaling to be expressed in the early CNC, is pivotal for CNC induction and migration in Xenopus. However, snai2 expression is silenced during CNC migration, and its roles at later developmental stages remain unclear. We generated a transgenic X. tropicalis line that expresses enhanced green fluorescent protein (eGFP) driven by the snai2 promoter/enhancer, and observed eGFP expression not only in the pre-migratory and migrating CNC, but also the differentiating CNC. This transgenic line can be used directly to detect deficiencies in CNC development at various stages, including subtle perturbation of CNC differentiation. In situ hybridization and immunohistochemistry confirm that Snai2 is re-expressed in the differentiating CNC. Using a separate transgenic Wnt reporter line, we show that canonical Wnt signaling is also active in the differentiating CNC. Blocking Wnt signaling shortly after CNC migration causes reduced snai2 expression and impaired differentiation of CNC-derived head cartilage structures. These results suggest that Wnt signaling is required for snai2 re-expression and CNC differentiation