Radio AGN in 13,240 galaxy clusters from the Sloan Digital Sky Survey

We correlate the positions of 13,240 Brightest Cluster Galaxies (BCGs) with 0.1 <= z <= 0.3 from the maxBCG catalog with radio sources from the FIRST survey to study the sizes and distributions of radio AGN in galaxy clusters. We find that 19.7% of our BCGs are associated with FIRST sources, and this fraction depends on the stellar mass of the BCG, and to a lesser extent on the richness of the parent cluster (in the sense of increasing radio loudness with increasing mass). The intrinsic size of the radio emission associated with the BCGs peaks at 55 kpc, with a tail extending to 200 kpc. The radio power of the extended sources places them on the divide between FR I and FR II type sources, while sources compact in the radio tend to be somewhat less radio-luminous. We also detect an excess of radio sources associated with the cluster, instead of with the BCG itself, extending out to ~1.4 Mpc.Comment: 14 pages, 6 figures, accepted for publication in ApJ

Peaks in the cosmological density field: parameter constraints from 2dF Galaxy Redshift Survey data

We use the number density of peaks in the smoothed cosmological density field taken from the 2dF Galaxy Redshift Survey to constrain parameters related to the power spectrum of mass fluctuations, n (the spectral index), dn/d(lnk) (rolling in the spectral index), and the neutrino mass, m_nu. In a companion paper we use N-body simulations to study how the peak density responds to changes in the power spectrum, the presence of redshift distortions and the relationship between galaxies and dark matter halos. In the present paper we make measurements of the peak density from 2dF Galaxy Redshift Survey data, for a range of smoothing filter scales from 4-33 h^-1 Mpc. We use these measurements to constrain the cosmological parameters, finding n=1.36 (+0.75)(-0.64), m_nu < 1.76 eV, dn/d(lnk)=-0.012 (+0.192)(-0.208), at the 68 % confidence level, where m_nu is the total mass of three massive neutrinos. At 95% confidence we find m_nu< 2.48 eV. These measurements represent an alternative way to constrain cosmological parameters to the usual direct fits to the galaxy power spectrum, and are expected to be relatively insensitive to non-linear clustering evolution and galaxy biasing.Comment: Accepted for Publication in MNRAS on Sept 25, 2009. Abstract modified to remove LaTex markup

Imaging and Spectroscopy of Ultra Steep Spectrum Radio Sources

We present a sample of 40 Ultra Steep Spectrum (USS, $\alpha \leq -1.3$, $S_{\nu}\propto \nu^{\alpha}$) radio sources selected from the Westerbork in the Southern Hemisphere (WISH) catalog. The USS sources have been imaged in K--band at the Cerro Tololo Inter-American Observatory (CTIO) and with the Very Large Telescope at Cerro Paranal. We also present VLT, Keck and Willian Herschel Telescope(WHT) optical spectroscopy of 14 targets selection from 4 different USS samples. For 12 sources, we have been able to determine the redshifts, including 4 new radio galaxies at z > 3. We find that most of our USS sources have predominantly small (6'') radio sizes and faint magnitudes (K~18). The mean K-band counterpart magnitude is $\bar{K}$=18.6. The expected redshift distribution estimated using the Hubble K-z diagram has a mean of $\bar{z}_{exp}$$\sim$2.13, which is higher than the predicted redshift obtained for the SUMSS-NVSS sample and the expected redshift obtained in the 6C$^{**}$ survey. The compact USS sample analyzed here may contain a higher fraction of galaxies which are high redshift and/or are heavily obscured by dust. Using the 74, 352 and 1400 MHz flux densities of a sub-sample, we construct a radio colour-colour diagram. We find that all but one of our USS sources have a strong tendency to flatten below 352 MHz. We also find that the highest redshift source from this paper (at z=3.84) does not show evidence for spectral flattening down to 151 MHz. This suggests that very low frequency selected USS samples will likely be more efficient to find high redshift galaxies.Comment: Accepted for publication in MNRAS, 14 pages including 44 PostScript figures and 4 tables. Version with all figures available from http://www.eso.org/~cdebreuc/papers.htm

Rejuvenating Power Spectra II: the Gaussianized galaxy density field

We find that, even in the presence of discreteness noise, a Gaussianizing transform (producing a more-Gaussian one-point distribution) reduces nonlinearities in the power spectra of cosmological matter and galaxy density fields, in many cases drastically. Although Gaussianization does increase the effective shot noise, it also increases the power spectrum's fidelity to the linear power spectrum on scales where the shot noise is negligible. Gaussianizing also increases the Fisher information in the power spectrum in all cases and resolutions, although the gains are smaller in redshift space than in real space. We also find that the gain in cumulative Fisher information from Gaussianizing peaks at a particular grid resolution that depends on the sampling level.Comment: Slight changes to match version accepted to ApJ. 7 pages, 8 figure

From Common Sense Concepts to Scientifically Conditioned Concepts of Chemical Bonding: An Historical and Textbook Approach Designed to Address Learning and Teaching Issues at the Secondary School Level

This paper selects six key alternative conceptions identified in the literature on student understandings of chemical bonding and illustrates how a historical analysis and a textbook analysis can inform these conceptions and lead to recommendations for improving the teaching and learning of chemical bonding at the secondary school level. The historical analysis and the textbook analysis focus on the concepts of charge, octet, electron pair, ionic, covalent and metallic bonding. Finally, a table of recommendations is made for teacher and student in the light of four fundamental questions and the six alternative conceptions to enhance the quality of the curriculum resources available and the level of student engagement

Optimality and uniqueness of the (4,10,1/6) spherical code

Linear programming bounds provide an elegant method to prove optimality and uniqueness of an (n,N,t) spherical code. However, this method does not apply to the parameters (4,10,1/6). We use semidefinite programming bounds instead to show that the Petersen code, which consists of the midpoints of the edges of the regular simplex in dimension 4, is the unique (4,10,1/6) spherical code.Comment: 12 pages, (v2) several small changes and corrections suggested by referees, accepted in Journal of Combinatorial Theory, Series

Extracellular vesicle interactions with the external and internal exposome in mediating carcinogenesis

The influence of environmental factors on an individual, from conception onwards, is defined as the exposome. It can be categorized into the external exposome, which includes external factors such as air pollution, chemical contaminants, and diet, and the internal exposome, which is unique to an individual, and involves age, physiology, and their genetic profile. The effect of external exposures on the internal exposome, or genetic profile, can be determined through omics analyses. However, this is often compromised due to low sample quantity and cost. Therefore, identification of other factors that can provide an insight into the cellular profile of an individual, provides an exciting avenue, and an emerging field is that of extracellular vesicles (EVs). Recently, our understanding of how cells can communicate with each other has shifted to recognise the role of EVs. EVs are secreted by all living cells, and have been identified in all biological fluids studied so far. They transport bioactive molecules (e.g., proteins, miRNAs, and DNA), and their release can be regulated by the cellular microenvironment. Analysis of EVs in respond to environmental factors might provide novel insights into the role of tumour EVs in carcinogenesis. Not only will EVs give some insight into the tumour cells themselves but they will also provide a better understanding of how cells communicate with one another, contributing to cancer progression. Moreover, characterising the content and functions of tumour-derived EVs has the potential to overcome the current challenges to improve cancer patient outcomes. For example, the identification of EVs targets for therapeutic interventions and tumour EVs biomarkers could facilitate the development of early screening for several cancers. The aim of this review, thus, is to discuss the overall role of EVs in response to the various external and internal signals in cancer. We will specifically highlight the biogenesis, secretion, and content of EVs in response to oncogenic transformation and metabolic regulators in cancer

Reactome - a knowledgebase of human biological pathways

Pathway curation is a powerful tool for systematically associating gene products with functions. Reactome (www.reactome.org) is a manually curated human pathway knowledgebase describing a wide range of biological processes in a computationally accessible manner. The core unit of the Reactome data model is the Reaction, whose instances form a network of biological interactions through entities that are consumed, produced, or act as catalysts. Entities are distinguished by their molecular identities and cellular locations. Set objects allow grouping of related entities. Curation is based on communication between expert authors and staff curators, facilitated by freely available data entry tools. Manually curated data are subjected to quality control and peer review by a second expert. Reactome data are released quarterly. At release time, electronic orthology inference performed on human data produces reaction predictions in 22 species ranging from mouse to bacteria. Cross-references to a large number of publicly available databases are attached, providing multiple entry points into the database. The Reactome Mart allows query submission and data retrieval from Reactome and across other databases. The SkyPainter tool provides visualization and statistical analysis of user supplied data, e.g. from microarray experiments. Reactome data are freely available in a number of data formats (e.g. BioPax, SBML)

Search Result Diversification in Short Text Streams

We consider the problem of search result diversification for streams of short texts. Diversifying search results in short text streams is more challenging than in the case of long documents, as it is difficult to capture the latent topics of short documents. To capture the changes of topics and the probabilities of documents for a given query at a specific time in a short text stream, we propose a dynamic Dirichlet multinomial mixture topic model, called D2M3, as well as a Gibbs sampling algorithm for the inference. We also propose a streaming diversification algorithm, SDA, that integrates the information captured by D2M3 with our proposed modified version of the PM-2 (Proportionality-based diversification Method -- second version) diversification algorithm. We conduct experiments on a Twitter dataset and find that SDA statistically significantly outperforms state-of-the-art non-streaming retrieval methods, plain streaming retrieval methods, as well as streaming diversification methods that use other dynamic topic models

Development of self-management in pediatric inflammatory bowel disease: a qualitative exploration

Background: Self-management programs in pediatric chronic conditions, such as asthma and diabetes were effective in improving health-related outcomes. Similarly, self-management in the context of adult in inflammatory bowel disease (IBD) safely reduced healthcare costs. Nevertheless, evidence on self-management in pediatric IBD is scant. This study aims to explore self-management in pediatric IBD by exploring the childhood experience of IBD and how it is understood by the participants. Methods: Using a constructivist grounded theory approach, seven participants aged 8-17 years old were recruited in a tertiary metropolitan pediatric IBD center. Semi-structured interviews using topic guides and optional draw-and-write methods were used for data collection. Multi-level coding and constant comparison methods were utilised during data analysis. Results: The pediatric IBD self-management theory described the phenomenon of self-management through the relationship of categories that emerged from the study. Self-management starts off as a parent-dominant process that progressed to a more autonomous form with increasing disease experience. The experience was described as filled with struggles and a developing sense of control in managing these struggles. Autonomous self-management developed from the interaction of information, insight and integration. Enablers and deterrents were the contextual factors that influenced the development of self-management. Conclusions: Establishing identity both as a psychosocial developmental task and a disease-specific task is the core of self-management in childhood IBD. Future self-management programs should explore the role of structures around the child (family, school and healthcare systems) and the implementation of a proactive philosophy of involving children in managing their condition