Oxygen Free-Radical Reduction of Brain Capillary Rubidium Uptake

Free radicals are proposed to play a role in the injury following cerebral ischemia in which cerebral edema is a prominent feature. To determine whether free radicals might alter the movement of ions and water across the blood-brain barrier, we examined their effect on brain capillary transport. Rat brain capillaries were isolated, incubated with a system that generates free radicals, and various capillary transport systems were studied. Rubidium uptake was reduced 74% whereas rubidium efflux, glucose transport, and capillary water space were unchanged. The results following the addition of radical scavengers indicated that hydrogen peroxide or a related free radical was the toxic species. These data suggest that free radicals can impair capillary endothelial cell mechanisms that help maintain homeostasis of electrolytes and water in brain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65815/1/j.1471-4159.1986.tb12981.x.pd

Measurement of Student Perceptions and Attitudes in Mathematics

As in other subjects, student perceptions of and attitudes towards mathematics play a role in their motivation and approaches to learning. This is of special concern in mathematics as so many students take terminal math courses at the post-secondary level as part of other programs. Ultimately, we are interested in how these attitudes influence further math course choices and student performance in the courses they do take, as well as instructional choices that can promote more expert-like attitudes.This academic year, our research group adapted an existing survey for Physics (the CLASS developed at U. Colorado), a measure of student orientation towards expert attitudes about the subject, which including perceptions of math as a field and (self-perceived) dispositions in math problem solving. We surveyed UBC students at the beginning and end of a range of early Math courses (primarily first-year calculus courses), as well as a variety of experts in our department (faculty, graduate students and post-docs). This has allowed us to assess student attitudes and perceptions, and to track how they shift over time, relative to an expert response. Similar adaptations of this survey exist for other science disciplines (see http://www.colorado.edu/sei/class/).In this presentation, I will discuss some existing tools in math and other disciplines for assessing student attitudes, review the development process we are following, and show highlights from our preliminary results

Gas rich galaxies from the FIGGS survey

The FIGGS (Faint Irregular Galaxy GMRT Survey) is aimed at creating a multi-wavelength observational data base for a volume limited sample of the faintest gas rich galaxies. In this paper we discuss two very gas rich galaxies that were observed as part of the FIGGS survey, viz. NGC 3741 and And IV. These galaxies are unusual in that they have extremely extended gas disks and very high ratios of dark to luminous matter. The very extended HI disks provide an unique opportunity to trace the extended distribution of dark matter around faint galaxies. We compare the baryon fraction of these galaxies with a sample of galaxies with well measured rotation curves and discuss whether extremely gas rich dwarf galaxies have abnormally small baryon fractions.Comment: 5 Pages, 4 Figures. To be published in the proceedings of "Galaxies in the Local Volume", ed. B. Koribalski, H. Jerje

Pathogenesis, Diagnosis and Management of Squamous Cell Carcinoma and Pseudoepithelial Hyperplasia Secondary to Red Ink Tattoo: A Case Series and Review

The increasing popularity of tattooing has paralleled an increase in associated cutaneous reactions. Red ink is notorious for eliciting cutaneous reactions. A common reaction is pseudoepitheliomatous hyperplasia (PEH), which is a benign condition closely simulating squamous cell carcinoma (SCC). Differentiating PEH from SCC is challenging for pathologists and clinicians alike. The exact pathogenesis of these lesions secondary to red ink is not known, and there are no sources outlining diagnostic and treatment options and their efficacy. We present four study cases with different pathologies associated to red ink tattoos including lichenoid reaction, granulomatous reaction, PEH, and an SCC. Additionally, an extensive review of 63 articles was performed to investigate pathogenesis, diagnostic approaches, and treatment options. Hypotheses surrounding pathogenesis include but are not limited to the carcinogenic components of pigments, their reaction with UV and the traumatic process of tattooing. Pathogenesis seems to be multifactorial. Full-thickness biopsies with follow-up is the recommended diagnostic approach. There is no evidence of a single universally successful treatment for PEH. Low-dose steroids are usually tried following a step up in lack of clinical response. For SCC lesions, full surgical excision is widely used. A focus on clinicians’ awareness of adverse reactions is key for prevention. Regulation of the unmonitored tattoo industry remains an ongoing problem

Variability of serial CT scans in subacute necrotizing encephalomyelopathy (leigh disease)

Computed tomographic (CT) brain scans of patients with subacute necrotizing encephalomyelopathy (SNE) may reveal focal lesions that correspond to sites of anatomic involvement of the disease. Three patients with SNE were followed with serial CT brain scans. In two patients radiographic abnormalities appeared well after the onset of clinical symptoms. In all three patients the radiographic lesions changed with time. This variability seen with serial scanning is an important feature of SNE.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25809/1/0000372.pd

Phase-field modeling of microstructural pattern formation during directional solidification of peritectic alloys without morphological instability

During the directional solidification of peritectic alloys, two stable solid phases (parent and peritectic) grow competitively into a metastable liquid phase of larger impurity content than either solid phase. When the parent or both solid phases are morphologically unstable, i.e., for a small temperature gradient/growth rate ratio ($G/v_p$), one solid phase usually outgrows and covers the other phase, leading to a cellular-dendritic array structure closely analogous to the one formed during monophase solidification of a dilute binary alloy. In contrast, when $G/v_p$ is large enough for both phases to be morphologically stable, the formation of the microstructurebecomes controlled by a subtle interplay between the nucleation and growth of the two solid phases. The structures that have been observed in this regime (in small samples where convection effect are suppressed) include alternate layers (bands) of the parent and peritectic phases perpendicular to the growth direction, which are formed by alternate nucleation and lateral spreading of one phase onto the other as proposed in a recent model [R. Trivedi, Metall. Mater. Trans. A 26, 1 (1995)], as well as partially filled bands (islands), where the peritectic phase does not fully cover the parent phase which grows continuously. We develop a phase-field model of peritectic solidification that incorporates nucleation processes in order to explore the formation of these structures. Simulations of this model shed light on the morphology transition from islands to bands, the dynamics of spreading of the peritectic phase on the parent phase following nucleation, which turns out to be characterized by a remarkably constant acceleration, and the types of growth morphology that one might expect to observe in large samples under purely diffusive growth conditions.Comment: Final version, minor revisions, 16 pages, 14 EPS figures, RevTe

Rayleigh-Taylor Instabilities in Type Ia Supernova Remnants undergoing Cosmic-Ray Particle Acceleration - Low Adiabatic Index Solutions

This study investigates the evolution of Rayleigh-Taylor (R-T) instabilities in Type Ia supernova remnants that are associated with a low adiabatic index gamma, where gamma < 5/3, which reflects the expected change in the supernova shock structure as a result of cosmic-ray particle acceleration. Extreme cases, such as the case with the maximum compression ratio that corresponds to gamma=1.1, are examined. As gamma decreases, the shock compression ratio rises, and an increasingly narrow inter shock region with a more pronounced initial mixture of R-T unstable gas is produced. Consequently, the remnant outline may be perturbed by small-amplitude, small-wavelength bumps. However, as the instability decays over time, the extent of convective mixing in terms of the ratio of the radius of the R-T fingers to the blast wave does not strongly depend on the value of gamma for gamma >= 1.2. As a result of the age of the remnant, the unstable gas cannot extend sufficiently far to form metal-enriched filaments of ejecta material close to the periphery of Tycho's supernova remnant. The consistency of the dynamic properties of Tycho's remnant with the adiabatic model gamma=5/3 reveals that the injection of cosmic rays is too weak to alter the shock structure. Even with very efficient acceleration of cosmic rays at the shock, significantly enhanced mixing is not expected in Type Ia supernova remnants.Comment: 11 pages, 10 figures, MNRAS, accepte

The effects of primordial non-Gaussianity on the cosmological reionization

We investigate the effects of non-Gaussianity in the primordial density field on the reionization history. We rely on a semi-analytic method to describe the processes acting on the intergalactic medium (IGM), relating the distribution of the ionizing sources to that of dark matter haloes. Extending previous work in the literature, we consider models in which the primordial non-Gaussianity is measured by the dimensionless non-linearity parameter f_NL, using the constraints recently obtained from cosmic microwave background data. We predict the ionized fraction and the optical depth at different cosmological epochs assuming two different kinds of non-Gaussianity, characterized by a scale-independent and a scale-dependent f_NL and comparing the results to those for the standard Gaussian scenario. We find that a positive f_NL enhances the formation of high-mass haloes at early epochs, when reionization begins, and, as a consequence, the IGM ionized fraction can grow by a factor up to 5 with respect to the corresponding Gaussian model. The increase of the filling factor has a small impact on the reionization optical depth and is of order ~ 10 per cent if a scale-dependent non-Gaussianity is assumed. Our predictions for non-Gaussian models are in agreement with the latest WMAP results within the error bars, but a higher precision is required to constrain the scale dependence of non-Gaussianity.Comment: 10 pages, 8 figures, minor changes to match the version accepted for publication by MNRA