The reionization of the universe: The feedback of galaxy formation on the intergalactic medium

The thermal and ionization evolution of a uniform intergalactic medium (IGM) composed of H and He, undergoing reionization, including the mean effect of gas clumps embedded in a smoothly distributed ambient gas were calculated. The rate equations for ionization and recombination were solved together with the equations of energy conservation, including the effects of cosmological expansion, radiative and Compton cooling, and the diffuse flux emitted by the gas, and radiative transfer. The contribution to the continuum opacity of the universe due to the observed quasar absorption line clouds (QALC'S) were included. A variety of sources of photoionization, including quasars and primeval galaxies, as well as the possibility that hydrodynamical processes deposit thermal energy in the IGM were considered. Applications of these calculations including the evolution of the Ly-alpha forest clouds are described. A self-consistent treatment of the thermal and ionization history of the intergalactic medium (IGM) must take account of the growth of structure in the universe, since the mean density of the IGM corresponds primarily to the time-varying uncollapsed fraction of the baryon-electron component of the matter, and the collapsed fraction, in turn, can have a feedback effect on this uncollapsed fraction by releasing ionizing radiation and thermal energy and by contributing to the opacity of the universe. The coupled evolution of the IGM and the emerging structure with a special focus on the reionization of the IGM, which is believed to have been completed by some redshift z is approximately greater than 4, as inferred from the absence of the Gunn-Peterson effect in the spectra of high z quasars, are studied. The results and implications of detailed, numerical calculations of the thermal and ionization balance and radiative transfer in a uniform IGM of H and He, including the mean effect of an evolving distribution of gas clumps embedded in a smoothly distributed ambient gas is described

STR-972: TOP-DOWN CONSTRUCTION OF THE NEW LRT OVERHEAD BRIDGE, KITCHENER, ONTARIO

A new Light Rail Transit (LRT) system is being constructed in Waterloo Region. The first phase of construction is scheduled for completion in 2017 and will connect Conestoga Mall in the City of Waterloo and Fairview Park Mall in the City of Kitchener, a distance of 19 km. The LRT route crosses the existing Conestoga Parkway (Highway 7/8) in Kitchener-Waterloo, requiring the construction of a new structure under the busy freeway. In 2014-15, the Ministry of Transportation, Ontario (MTO) administered the construction of the new single span bridge using a unique top-down construction technique

Highly Ionized High-Velocity Clouds toward PKS 2155-304 and Markarian 509

To gain insight into four highly ionized high-velocity clouds (HVCs) discovered by Sembach et al. (1999), we have analyzed data from the Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) for the PKS 2155-304 and Mrk 509 sight lines. We measure strong absorption in OVI and column densities of multiple ionization stages of silicon (SiII/III/IV) and carbon (CII/III/IV). We interpret this ionization pattern as a multiphase medium that contains both collisionally ionized and photoionized gas. Toward PKS 2155-304, for HVCs at -140 and -270 km/s, respectively, we measure logN(OVI)=13.80+/-0.03 and log N(OVI)=13.56+/-0.06; from Lyman series absorption, we find log N(HI)=16.37^(+0.22)_(-0.14) and 15.23^(+0.38)_(-0.22). The presence of high-velocity OVI spread over a broad (100 km/s) profile, together with large amounts of low-ionization species, is difficult to reconcile with the low densities, n=5x10^(-6) cm^(-3), in the collisional/photoionization models of Nicastro et al. (2002), although the HVCs show a similar relation in N(SiIV)/N(CIV) versus N(CII)/N(CIV) as high-z intergalactic clouds. Our results suggest that the high-velocity OVI in these absorbers do not necessarily trace the WHIM, but instead may trace HVCs with low total hydrogen column density. We propose that the broad high-velocity OVI absorption arises from shock ionization, at bowshock interfaces produced from infalling clumps of gas with velocity shear. The similar ratios of high ions for HVC Complex C and these highly ionized HVCs suggest a common production mechanism in the Galactic halo.Comment: 38 pages, including 10 figures. ApJ, 10 April, 2004. Replaced with accepted versio

Antonio Gramsci’s impact on critical pedagogy

This paper provides an account of Antonio Gramsci’s impact on the area of critical pedagogy. It indicates the Gramscian influence on the thinking of major exponents of the field. It foregrounds Gramsci's ideas and then indicates how they have been taken up by a selection of critical pedagogy exponents who were chosen on the strength of their identification and engagement with Gramsci's ideas, some of them even having written entire essays on Gramsci. The essay concludes with a discussion concerning an aspect of Gramsci's concerns, the question of powerful knowledge, which, in the present author's view, provides a formidable challenge to critical pedagogues.peer-reviewe

Discovery of a Dwarf Post-Starburst Galaxy Near a High Column Density Ly-alpha Absorber

We report the discovery of a dwarf (M_B = -13.9) post-starburst galaxy coincident in recession velocity (within uncertainties) with the highest column density absorber (N_HI = 10^15.85 cm^{-2} at cz = 1586 km/s) in the 3C~273 sightline. This galaxy is by far the closest galaxy to this absorber, projected just 71 kpc on the sky from the sightline. The mean properties of the stellar populations in this galaxy are consistent with a massive starburst ~3.5 Gyrs ago, whose attendant supernovae, we argue, could have driven sufficient gas from this galaxy to explain the nearby absorber. Beyond the proximity on the sky and in recession velocity, the further evidence in favor of this conclusion includes both a match in the metallicities of absorber and galaxy, and the fact that the absorber has an overabundance of Si/C, suggesting recent type II supernova enrichment. Thus, this galaxy and its ejecta are the expected intermediate stage in the fading dwarf evolutionary sequence envisioned by Babul & Rees to explain the abundance of faint blue galaxies at intermediate redshifts.Comment: 33 pages, 4 figures, ApJ in pres

Towards a framework for critical citizenship education

Increasingly countries around the world are promoting forms of "critical" citizenship in the planned curricula of schools. However, the intended meaning behind this term varies markedly and can range from a set of creative and technical skills under the label "critical thinking" to a desire to encourage engagement, action and political emancipation, often labelled "critical pedagogy". This paper distinguishes these manifestations of the "critical" and, based on an analysis of the prevailing models of critical pedagogy and citizenship education, develops a conceptual framework for analysing and comparing the nature of critical citizenship

Parental Tobacco Use: Impact on Child Emotion Identification Ability

Although the physical effects of tobacco on an individual are well-known, the impacts that smoking has on social skills of family members are less understood. The ability for children to identify emotions is crucial for normal social functioning, and the impact of parental tobacco use during child development of this skill is not known. The proposed research compares parent-reported tobacco use to child emotion identification ability (EIA). Information regarding parental tobacco use history was gathered from a structured diagnostic interview of DSM-IV symptoms called the Composite International Diagnostic Interview. Child EIA was assessed using a paradigm called Emotional Faces, which presented photos of faces expressing different emotions at different strengths. Ability was determined based on the percentage of emotions that the child correctly identified. Exposure to parental smoking both during childhood and prior to birth was related to significantly lower child EIA compared to the EIA of children whose parents never smoked, while covariates of gender, SES, birth weight, race, and ethnicity were not significant. However, there was a significant main effect of age which, when added to the model, overwhelmed the significance of parental smoking on EIA. Upon further investigation into EIA for carrying strengths of emotion expressions, significant differences in EIA were found between children whose parents had never used tobacco, and those whose parents has used tobacco during the first decade of the child’s life for child identification of moderate amounts of emotion (expression strengths of 60% and 40%), regardless of the effect of age. No significant differences were found among the groups for the stronger expression strengths of 100 and 80. The findings of this study suggest that parental tobacco use during the early years of a child’s life when social skills are developing may negatively impact the child’s EIA, especially in situations where they are presented with more ambiguous emotional information. As more is understood about the familial impacts from tobacco use, more effective cessation programs can be developed, and better interventions for children with decreased EIA can be explored

Sex and the Cinema: What American Pie Teaches the Young

This paper focuses upon the wildly successful blockbuster American Pie teenpics, especially American Pie 3 – the Wedding. I argue that these films, which are sited so securely within the visual and pedagogical machinery of Hollywood culture, are specifically designed to appeal to teenage male audiences, and to provide lessons in sex and romance. Movies like this are especially important as they are experienced by far more teenagers than, for example, instructional films or other classroom materials; indeed, as Henry Giroux has observed, "teens and youth learn how to define themselves outside of the traditional sites of instruction, such as the home and the school… Learning in the postmodern age is located elsewhere – in popular spheres that shape their identities, through forms of knowledge and desires that appear absent from what is taught in schools" (Giroux, 1997, p.49). In this paper I discuss whether the American Pie series is actually a "new age" effort which, via insubordinate performances of gender, contests the hegemonic field of signification which regulates the production of sex, gender and desire, or whether it is more accurately described as a retrogressive hetero-conservative opus with a veneer of sexual radicalism. In short, I intend to probe whether this filmic vector for sex education is all about the shaping of responsible, caring, vulnerable men, or is it guiding them to become just like their heterosexual, middle-class fathers? And whether, despite its riotous and raunchy advertising, American Pie really dishes up something spicy or something terribly wholesome instead

Tight Beltrami fields with symmetry

Let $M$ be a compact orientable Seifered fibered 3-manifold without a boundary, and $\alpha$ an $S^1$-invariant contact form on $M$. In a suitable adapted Riemannian metric to $\alpha$, we provide a bound for the volume $\text{Vol}(M)$ and the curvature, which implies the universal tightness of the contact structure $\xi=\ker\alpha$.Comment: 26 page