The Bias of the Log Power Spectrum for Discrete Surveys

A primary goal of galaxy surveys is to tighten constraints on cosmological parameters, and the power spectrum $P(k)$ is the standard means of doing so. However, at translinear scales $P(k)$ is blind to much of these surveys' information---information which the log density power spectrum recovers. For discrete fields (such as the galaxy density), $A^*$ denotes the statistic analogous to the log density: $A^*$ is a "sufficient statistic" in that its power spectrum (and mean) capture virtually all of a discrete survey's information. However, the power spectrum of $A^*$ is biased with respect to the corresponding log spectrum for continuous fields, and to use $P_{A^*}(k)$ to constrain the values of cosmological parameters, we require some means of predicting this bias. Here we present a prescription for doing so; for Euclid-like surveys (with cubical cells 16$h^{-1}$ Mpc across) our bias prescription's error is less than 3 per cent. This prediction will facilitate optimal utilization of the information in future galaxy surveys.Comment: 5 pages, 4 figures; published in MNRASL (here updated to published version

The science of short exposures: Hubble SNAPshot observations of massive galaxy clusters

Hubble Space Telescope SNAPshot surveys of 86 X-ray selected galaxy clusters at $0.3 < z < 0.5$ from the MACS sample have proven invaluable for the exploration of a wide range of astronomical research topics. We here present an overview of the four MACS SNAPshot surveys conducted from Cycle 14 to Cycle 20 as part of a long-term effort aimed at identifying exceptional cluster targets for in-depth follow up by the extragalactic community. We also release redshifts and X-ray luminosities of all clusters observed as part of this initiative. To illustrate the power of SNAPshot observations of MACS clusters, we explore several aspects of galaxy evolution illuminated by the images obtained for these programmes. We confirm the high lensing efficiency of X-ray selected clusters at $z>0.3$. Examining the evolution of the slope of the cluster red sequence, we observe at best a slight decrease with redshift, indicating minimal age contribution since $z\sim 1$. Congruent to previous studies' findings, we note that the two BCGs which are significantly bluer ($\geq 5\sigma$) than their clusters' red sequences reside in relaxed clusters and exhibit pronounced internal structure. Thanks to our targets' high X-ray luminosity, the subset of our sample observed with Chandra adds valuable leverage to the X-ray luminosity--optical richness relation, which, albeit with substantial scatter, is now clearly established from groups to extremely massive clusters of galaxies. We conclude that SNAPshot observations of MACS clusters stand to continue to play a vital pathfinder role for astrophysical investigations across the entire electromagnetic spectrum.Comment: 22 pages, 6 tables, 15 figures; published in MNRAS. Final published form posted with this revisio

The Impact of Non-Gaussianity upon Cosmological Forecasts

The primary science driver for 3D galaxy surveys is their potential to constrain cosmological parameters. Forecasts of these surveys' effectiveness typically assume Gaussian statistics for the underlying matter density, despite the fact that the actual distribution is decidedly non-Gaussian. To quantify the effect of this assumption, we employ an analytic expression for the power spectrum covariance matrix to calculate the Fisher information for BAO-type model surveys. We find that for typical number densities, at $k_\mathrm{max} = 0.5 h$ Mpc$^{-1}$, Gaussian assumptions significantly overestimate the information on all parameters considered, in some cases by up to an order of magnitude. However, after marginalizing over a six-parameter set, the form of the covariance matrix (dictated by $N$-body simulations) causes the majority of the effect to shift to the "amplitude-like" parameters, leaving the others virtually unaffected. We find that Gaussian assumptions at such wavenumbers can underestimate the dark energy parameter errors by well over 50 per cent, producing dark energy figures of merit almost 3 times too large. Thus, for 3D galaxy surveys probing the non-linear regime, proper consideration of non-Gaussian effects is essential.Comment: 9 pages, 5 figures, submitted to MNRA

Extracting News Events from Microblogs

Twitter stream has become a large source of information for many people, but the magnitude of tweets and the noisy nature of its content have made harvesting the knowledge from Twitter a challenging task for researchers for a long time. Aiming at overcoming some of the main challenges of extracting the hidden information from tweet streams, this work proposes a new approach for real-time detection of news events from the Twitter stream. We divide our approach into three steps. The first step is to use a neural network or deep learning to detect news-relevant tweets from the stream. The second step is to apply a novel streaming data clustering algorithm to the detected news tweets to form news events. The third and final step is to rank the detected events based on the size of the event clusters and growth speed of the tweet frequencies. We evaluate the proposed system on a large, publicly available corpus of annotated news events from Twitter. As part of the evaluation, we compare our approach with a related state-of-the-art solution. Overall, our experiments and user-based evaluation show that our approach on detecting current (real) news events delivers a state-of-the-art performance

Active-Learning Quality Improvement Training Curriculum for Faculty in Hospital Medicine

Background: There is a growing emphasis on teaching Quality Improvement (QI) to resident physicians and medical students. However, faculty with QI skills and knowledge is lacking at many academic medical centers.Active learning programs to improve faculty capacity for QI have shown positive outcomes. We sought to develop a QI curriculum for faculty within the Division of Hospital Medicine. Description of project/program/innovation: We conducted a needs assessment focus group for Hospital Medicine faculty at our academic medical center. Six faculty members participated and identified priorities and potential challenges. Based on the focus group feedback, we designed a 12-session curriculum that uses an active-learning approach to teach core concepts in QI and includes sessions on effectively mentoring and publishing QI (Table 1). Junior and senior faculty collaborated on curricular design and delivery, with the goal of developing junior faculty into effective QI teachers. Pre-assessment of QI knowledge, skills, and attitudes was conducted using a survey instrument and the revised Quality Improvement Knowledge Application Tool (QIKAT-R). Results: Eighteen faculty completed the pre-assessments (82% completion). At baseline, self-reported comfort was highest for “setting aims for a QI project” and lowest for “presenting results of a QI project”. The mean QIKAT-R score was 16.8 out of 27 (SD 4.5), with the lowest performance in the “setting aims” domain. To date, six sessions have been completed. The selected project focuses on improving hospitalized patients’ experiences around daily bedside rounding. Discussion: We have created a QI curriculum that seeks to address the gap in QI skills among hospitalists. Pre-assessments revealed poor correlation between self-reported comfort level and QIKAT-R scores within each domain, further highlighting educational opportunities. We plan to use feedback from this pilot to refine the curriculum and offer it to faculty in other specialties

Embodied Rhythm: Commentary on "The Contribution of Anthropometric Factors to Individual Differences in the Perception of Rhythm" by Neil P. McAngus Todd, Rosanna Cousins, and Christopher S. Lee

Todd, Cousins, and Lee (2007) have presented some intriguing data suggesting that body size, as measured by standard anthropometric indices, is related to the preferred beat period in a perceptual task. Curiously, however, they did not find a significant sex difference, even though the women in their sample were clearly smaller than the men. Another recent study of preferred spontaneous tempo (McAuley et al., 2006) likewise failed to find a sex difference in a large sample of young adults. It is unclear why body size should have an effect only within each sex group

High bandwidth magnetically isolated signal transmission circuit

Many current electronic systems incorporate expensive or sensitive electrical components. Because electrical energy is often generated or transmitted at high voltages, the power supplies to these electronic systems must be carefully designed. Power supply design must ensure that the electrical system being supplied with power is not exposed to excessive voltages or currents. In order to isolate power supplies from electrical equipment, many methods have been employed. These methods typically involve control systems or signal transfer methods. However, these methods are not always suitable because of their drawbacks. The present invention relates to transmitting information across an interface. More specifically, the present invention provides an apparatus for transmitting both AC and DC information across a high bandwidth magnetic interface with low distortion

The Small World of Osteocytes: Connectomics of the Lacuno-Canalicular Network in Bone

Osteocytes and their cell processes reside in a large, interconnected network of voids pervading the mineralized bone matrix of most vertebrates. This osteocyte lacuno-canalicular network (OLCN) is believed to play important roles in mechanosensing, mineral homeostasis, and for the mechanical properties of bone. While the extracellular matrix structure of bone is extensively studied on ultrastructural and macroscopic scales, there is a lack of quantitative knowledge on how the cellular network is organized. Using a recently introduced imaging and quantification approach, we analyze the OLCN in different bone types from mouse and sheep that exhibit different degrees of structural organization not only of the cell network but also of the fibrous matrix deposited by the cells. We define a number of robust, quantitative measures that are derived from the theory of complex networks. These measures enable us to gain insights into how efficient the network is organized with regard to intercellular transport and communication. Our analysis shows that the cell network in regularly organized, slow-growing bone tissue from sheep is less connected, but more efficiently organized compared to irregular and fast-growing bone tissue from mice. On the level of statistical topological properties (edges per node, edge length and degree distribution), both network types are indistinguishable, highlighting that despite pronounced differences at the tissue level, the topological architecture of the osteocyte canalicular network at the subcellular level may be independent of species and bone type. Our results suggest a universal mechanism underlying the self-organization of individual cells into a large, interconnected network during bone formation and mineralization