The black-white education-scaled test-score gap in grades k-7

We measure the black-white achievement gap from kindergarten through seventh grade on an interval scale created by tying each grade/test score combination to average eventual education. After correcting for various sources of test measurement error, some of which are unique to forward-looking scales, we find no racial component in the evolution of the achievement gap through the first eight years of schooling. Further, most, if not all, of the gap can be explained by socioeconomic differences. Our results suggest that the rising racial test gap in previous studies probably reflects excessive measurement error in testing in the early grades.Accepted manuscrip

Constraints on dark energy and cosmic topology

A non-trivial spatial topology of the Universe is a potentially observable attribute, which can be probed through the circles-in-the-sky for all locally homogeneous and isotropic universes with no assumptions on the cosmological parameters. We show how one can use a possible circles-in-the-sky detection of the spatial topology of globally homogeneous universes to set constraints on the dark energy equation of state parameters.Comment: 6 pages, 1 figure. To appear in Int. J. Mod. Phys. A (2009). From a talk presented at the Seventh Alexander Friedmann International Seminar on Gravitation and Cosmolog

How Filaments are Woven into the Cosmic Web

Observations indicate galaxies are distributed in a filament-dominated web-like structure. Numerical experiments at high and low redshift of viable structure formation theories also show filament-dominance. We present a simple quantitative explanation of why this is so, showing that the final-state web is actually present in embryonic form in the overdensity pattern of the initial fluctuations, with nonlinear dynamics just sharpening the image. The web is largely defined by the position and primordial tidal fields of rare events in the medium, with the strongest filaments between nearby clusters whose tidal tensors are nearly aligned. Applications of the cosmic web theory to observations include probing cluster-cluster bridges by weak gravitational lensing, X-rays, and the Sunyaev-Zeldovich effect and probing high redshift galaxy-galaxy bridges by low column density Lyman alpha absorption lines.Comment: 9 pages, gzipped uuencoded postscript file, 4 figures in separate files. The text + figures are also available from anonymous ftp site: ftp://ftp.cita.utoronto.ca/ftp/cita/bond/bkp_natur

CMB Polarization Experiments

We discuss the analysis of polarization experiments with particular emphasis on those that measure the Stokes parameters on a ring on the sky. We discuss the ability of these experiments to separate the $E$ and $B$ contributions to the polarization signal. The experiment being developed at Wisconsin university is studied in detail, it will be sensitive to both Stokes parameters and will concentrate on large scale polarization, scanning a $47^o$ degree ring. We will also consider another example, an experiment that measures one of the Stokes parameters in a $1^o$ ring. We find that the small ring experiment will be able to detect cosmological polarization for some models consistent with the current temperature anisotropy data, for reasonable integration times. In most cosmological models large scale polarization is too small to be detected by the Wisconsin experiment, but because both $Q$ and $U$ are measured, separate constraints can be set on $E$ and $B$ polarization.Comment: 27 pages with 12 included figure

Separating the effects of experimental noise from inherent system variability in voltammetry: the [[Fe(CN)6]3−/4−_6]^{3-/ 4-} process

Recently, we have introduced the use of techniques drawn from Bayesian statistics to recover kinetic and thermodynamic parameters from voltammetric data, and were able to show that the technique of large amplitude ac voltammetry yielded significantly more accurate parameter values than the equivalent dc approach. In this paper we build on this work to show that this approach allows us, for the first time, to separate the effects of random experimental noise and inherent system variability in voltammetric experiments. We analyse ten repeated experimental data sets for the $[$Fe(CN)$_6]^{3-/ 4-}$ process, again using large-amplitude ac cyclic voltammetry. In each of the ten cases we are able to obtain an extremely good fit to the experimental data and obtain very narrow distributions of the recovered parameters governing both the faradaic (the reversible formal faradaic potential, $E_0$, the standard heterogeneous charge transfer rate constant $k_0$, and the charge transfer coefficient $\alpha$) and non-faradaic terms (uncompensated resistance, $R_u$, and double layer capacitance, $C_{dl}$). We then employ hierarchical Bayesian methods to recover the underlying "hyperdistribution" of the faradaic and non-faradaic parameters, showing that in general the variation between the experimental data sets is significantly greater than suggested by individual experiments, except for $\alpha$ where the inter-experiment variation was relatively minor. Correlations between pairs of parameters are provided, and for example, reveal a weak link between $k_0$ and $C_{dl}$ (surface activity of a glassy carbon electrode surface). Finally, we discuss the implications of our findings for voltammetric experiments more generally.Comment: 30 pages, 6 figure

EXPLORING SUCCESS AND CHALLENGES OF BLACK STUDENTS TAKING AN ENGLISH COURSE ONLINE AT AN URBAN COMMUNITY COLLEGE

Community colleges have expanded access to higher education and were early adopters of online courses. Among literature on online course performance, Black students are least successful in online learning despite being one of the growing populations at community colleges. This case study investigated the experiences of Black community college students taking an online English course for the first time. These experiences were particularly unique because the students participated during the Covid-19 pandemic. The findings indicate that students navigate multiple priorities outside of school, technology challenges, and desire for increased preparation, representation, and support from the campus community. This study assists in expanding the limited research on Black community college students\u27 experiences online. Growing technology adaptation within education necessitates conversation around online learning structure and supports so virtual spaces can be a tool to address existing inequities, so all students reach success