Redressing racial inequities through water law in South Africa: revisiting old contradictions? Draft

Water lawCatchment areasRiver basinsSocial aspectsPovertyInstitutional development

Initial Ionization of Compressible Turbulence

We study the effects of the initial conditions of turbulent molecular clouds on the ionization structure in newly formed H_{ii} regions, using three-dimensional, photon-conserving radiative transfer in a pre-computed density field from three-dimensional compressible turbulence. Our results show that the initial density structure of the gas cloud can play an important role in the resulting structure of the H_{ii} region. The propagation of the ionization fronts, the shape of the resulting H_{ii} region, and the total mass ionized depend on the properties of the turbulent density field. Cuts through the ionized regions generally show ``butterfly'' shapes rather than spherical ones, while emission measure maps are more spherical if the turbulence is driven on scales small compared to the size of the H_{ii} region. The ionization structure can be described by an effective clumping factor $\zeta=< n > \cdot /^2$, where $n$ is number density of the gas. The larger the value of $\zeta$, the less mass is ionized, and the more irregular the H_{ii} region shapes. Because we do not follow dynamics, our results apply only to the early stage of ionization when the speed of the ionization fronts remains much larger than the sound speed of the ionized gas, or Alfv\'en speed in magnetized clouds if it is larger, so that the dynamical effects can be negligible.Comment: 9 pages, 10 figures, version with high quality color images can be found in http://research.amnh.org/~yuexing/astro-ph/0407249.pd

Chemical Abundance Gradients in the Star-Forming Ring Galaxies

Ring waves of star formation, propagating outwardly in the galactic disks, leave chemical abundance gradients in their wakes. We show that the relative [Fe/O] abundance gradients in ring galaxies can be used as a tool for determining the role of the SNIa explosions in their chemical enrichment. We consider two mechanisms which can create outwardly propagating star forming rings in a purely gaseous disk -- a self-induced wave and a density wave, and demonstrate that the radial distribution of the relative [Fe/O] abundance gradients does not depend on the particular mechanism of the wave formation or on the parameters of the star-forming process. We show that the [Fe/O] profile is determined by the velocity of the wave, initial mass function, and the initial chemical composition of the star-forming gas. If the role of SNIa explosions is negligible in the chemical enrichment, the ratio [Fe/O] remains constant throughout the galactic disk with a steep gradient at the wave front. If SNIa stars are important in the production of cosmic iron, the [Fe/O] ratio has gradient in the wake of the star-forming wave with the value depending on the frequency of SNIa explosions.Comment: Uses aas2pp4.sty and epsfig.sty, 7 pages including one figure To appear in Astrophysical Journa

Migraine and vascular disease biomarkers: A population-based case-control study.

Background The underpinnings of the migraine-stroke association remain uncertain, but endothelial activation is a potential mechanism. We evaluated the association of migraine and vascular disease biomarkers in a community-based population. Methods Participants (300 women, 117 men) were recruited as a part of the Dutch CAMERA 1 (Cerebral Abnormalities in Migraine, an Epidemiologic Risk Analysis) study. Participants were aged 30-60 (mean 48) years, 155 migraine had with aura (MA), 128 migraine without aura (MO), and 134 were controls with no severe headaches. Plasma concentrations of fibrinogen, Factor II, D-dimer, high sensitivity C-reactive protein (hs-CRP), and von Willebrand factor antigen were compared between groups, also stratifying by sex. Results Fibrinogen and hs-CRP were elevated in migraineurs compared to controls. In logistic regression analyses, MO and MA had increased likelihood of elevated fibrinogen, and MA had increased likelihood of elevated Factor II and hs-CRP. Fibrinogen and Factor II were associated with MA in women but not men. In the migraine subgroup, the total number of years of aura, but not headache, predicted elevated hs-CRP, and the average number of aura, but not headache, attacks predicted all biomarkers but Factor II. Conclusions Elevated vascular biomarkers were associated with migraine, particularly MA, as well as with years of aura and number of aura attacks

Using metamemory measures and memory tests to estimate eyewitness free recall performance

Using a mock witness methodology, we investigated the predictive value of metamemory measures and objective memory tests as indicators of eyewitness free recall performance. Participants (n = 208) first completed a metamemory assessment that included assessments of self-rated memory capacity, memory development and use of strategies. In a separate session, participants watched a mock-crime video and provided a free recall account, followed by one out of four independent memory tests (i.e., free recall, cued recall, face recognition and general knowledge). Accuracy, amount of details reported, confidence and over/underconfidence in the eyewitness free recall were the main dependent variables. Results indicated three main findings: (1) subjective assessments of memory capacity were not related to eyewitness free recall performance; (2) although individual confidence and over/underconfidence was somewhat stable across different memory tests, accuracy was less stable; and (3) individuals with higher self-rated memory capacity had a slightly stronger confidence-accuracy relation in free recall. These results are discussed with respect to metamemory assessments and performance stability across memory tests of different domains

A Case Concerning Children's False Memories of Abuse: Recommendations Regarding Expert Witness Work

Expert witnesses can play a major role in legal cases concerning the reliability of statements. Abuse cases frequently contain only the memories of eyewitnesses/victims without the presence of physical evidence. Here, it is of the utmost importance that expert witnesses use scientific evidence for their expert opinion. In this case report, a case is described in which 20 children reported being sexually abused by the same teachers at their elementary school. The investigative steps that were taken by the police and school authorities are reviewed, including how they probably affected memory. In order to provide a sound expert opinion regarding the reliability of these statements, three recommendations are proposed. To reduce the effect of confirmation bias and increase objectivity, it is argued that expert witnesses’ reports should contain alternative scenarios, be checked by another expert, and focus on the origin and context of the first statement

Sulfur, Chlorine, & Argon Abundances in Planetary Nebulae. I: Observations and Abundances in a Northern Sample

This paper is the first of a series specifically studying the abundances of sulfur, chlorine, and argon in Type II planetary nebulae (PNe) in the Galactic disk. Ratios of S/O, Cl/O, and Ar/O constitute important tests of differential nucleosynthesis of these elements and serve as strict constraints on massive star yield predictions. We present new ground-based optical spectra extending from 3600-9600 Angstroms for a sample of 19 Type II northern PNe. This range includes the strong near infrared lines of [S III] 9069,9532, which allows us to test extensively their effectiveness as sulfur abundance indicators. We also introduce a new, model-tested ionization correction factor for sulfur. For the present sample, we find average values of S/O=1.2E-2(+/- 0.71E-2), Cl/O=3.3E-4(+/- 1.6E-4), and Ar/O=5.0E-3(+/- 1.9E-3).Comment: 44 pages, 6 figures. Accepted for publication in the Astrophysical Journa

Angular diameters, fluxes and extinction of compact planetary nebulae: further evidence for steeper extinction towards the Bulge

We present values for angular diameter, flux and extinction for 70 Galactic planetary nebulae observed using narrow band filters. Angular diameters are derived using constant emissivity shell and photoionization line emission models. The mean of the results from these two models are presented as our best estimate. Contour plots of 36 fully resolved objects are included and the low intensity contours often reveal an elliptical structure that is not always apparent from FWHM measurements. Flux densities are determined, and for both H-alpha and O[III] there is little evidence of any systematic differences between observed and catalogued values. Observed H-alpha extinction values are determined using observed H-alpha and catalogued radio fluxes. H-alpha extinction values are also derived from catalogued H-alpha and H-beta flux values by means of an Rv dependent extinction law. Rv is then calculated in terms of observed extinction values and catalogued H-alpha and H-beta flux values. Comparing observed and catalogue extinction values for a subset of Bulge objects, observed values tend to be lower than catalogue values calculated with Rv = 3.1. For the same subset we calculate = 2.0, confirming that toward the Bulge interstellar extinction is steeper than Rv = 3.1. For the inner Galaxy a relation with the higher supernova rate is suggested, and that the low-density warm ionized medium is the site of the anomalous extinction. Lowvalues of extinction are also derived using dust models with a turnover radius of 0.08 microns.Comment: Accepted by MNRAS. 17 pages, 9 figures (including 36 contour plots of PNe), 5 Tables (including 2 large tables of angular diameters, fluxes and extinction

Linking the Metallicity Distribution of Galactic Halo Stars to the Enrichment History of the Universe

We compare the metallicity distribution of Galactic Halo stars with 3D realizations of hierarchical galaxy formation. Outflows from dwarf galaxies enrich the intergalactic medium inhomogeneously, at a rate depending on the local galaxy density. Consequently, the first stars created in small early-forming galaxies are less metal-rich that the first stars formed in more massive galaxies which typically form later. As most halo stars are likely to originate in accreted dwarfs, while disk stars formed out of outflow-enriched gas, this scenario naturally generates a ``metallicity floor'' for old disk stars, which we find to be roughly coincident with the higher end of our predicted metallicity distribution of halo stars, in agreement with observations. The broad and centrally peaked distribution of halo star metallicities is well reproduced in our models, with a natural dispersion depending on the exact accretion history. Our modeling includes the important ``baryonic stripping'' effect of early outflows, which brush away the tenuously held gas in neighboring pre-virialized density perturbations. This stripping process does not significantly modify the predicted shape of the halo star metal distribution but inhibits star-formation and hence the number of accreted stars, helping to reproduce the observed total Galactic halo luminosity and also the lack of low-luminosity local dwarf galaxies relative to N-body predictions.Comment: 5 pages, 1 figure, ApJ Letters, accepte