Central America Landmine Survivors: The Need for Action in Nicaragua

Landmines are indiscriminate weapons, wounding and killing not only soldiers but women and children as well. Although hostilities may cease, landmines continue to maim and kill 500 victims a week, the equivalent of 26,000 additional disabled persons each year. There are at least 250,000 landmine-disabled people in the world, and the number continues to grow

Manufacturing concern: Worthy and unworthy victims. Headline coverage of male and female victims of violence in Canadian daily newspapers, 1989 to 1992

This thesis examines the portrayal of male and female victims of violence in the headlines of seven Canadian daily newspapers between 1989 and 1992. Headlines were gathered from The Canadian Newspaper Index. Women\u27s and men\u27s victimization was found to receive different types and amounts of coverage. This coverage is inconsistent with known rates of violence against women and men, and I suggest three reasons for the disparities. I conclude by considering the possible consequences such coverage has for public perceptions and public policy

Training the Trainers in Community-Based Rehabilitation

Queen’s University and the Pan-American Health Organization are collaborating on a project called Community-Based Rehabilitation, designed to aid survivors. The project assists victims with their physical, emotional and financial problems to help them reenter and remain active in their communities

Do Childhood Vaccines Have Non-Specific Effects on Mortality

A recent article by Kristensen et al. suggested that measles vaccine and bacille Calmette–Guérin (BCG) vaccine might\ud reduce mortality beyond what is expected simply from protection against measles and tuberculosis. Previous reviews of the potential effects of childhood vaccines on mortality have not considered methodological features of reviewed studies. Methodological considerations play an especially important role in observational assessments, in which selection factors for vaccination may be difficult to ascertain. We reviewed 782 English language articles on vaccines and childhood mortality and found only a few whose design met the criteria for methodological rigor. The data reviewed suggest that measles vaccine delivers its promised reduction in mortality, but there is insufficient evidence to suggest a mortality benefit above that caused by its effect on measles disease and its sequelae. Our review of the available data in the literature reinforces how difficult answering these considerations has been and how important study design will be in determining the effect of specific vaccines on all-cause mortality.\u

Numerical solution of a class of random boundary value problems

AbstractThis paper deals with the nonlinear two point boundary value problem y″ = f(x, y, y′, R1,…, Rn), x0 < x < xf S1y(x0) + S2 y′(x0) = S3, S4 y(xf) + S5 y′(xf) = S6 where R1,…, Rn, S1,…, S6 are bounded continuous random variables. An approximate probability distribution function for y(x) is constructed by numerical integration of a set of related deterministic problems. Two distinct methods are described, and in each case convergence of the approximate distribution function to the actual distribution function is established. Primary attention is placed on problems with two random variables, but various generalizations are noted. As an example, a nonlinear one-dimensional heat conduction problem containing one or two random variables is studied in some detail

The sulfur isotope evolution of magmatic-hydrothermal fluids : insights into ore-forming processes

This project was supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 689909. W.H. also acknowledges support from a UKRI Future Leaders Fellowship (MR/S033505/1). A.J.B. is funded by the NERC National Environment Isotope Facility award (NE/S011587/1) and the Scottish Universities Environmental Research Centre.Metal-rich fluids that circulate in magmatic-hydrothermal environments form a wide array of economically significant ore deposits. Unravelling the origins and evolution of these fluids is crucial for understanding how Earth’s metal resources form and one of the most widely used tools for tracking these processes is sulfur isotopes. It is well established that S isotopes record valuable information about the source of the fluid, as well as its physical and chemical evolution (i.e. changing pH, redox and temperature), but it is often challenging to unravel which of these competing processes drives isotopic variability. Here we use thermodynamic models to predict S isotope fractionation for geologically realistic hydrothermal fluids and attempt to disentangle the effects of fluid sources, physico-chemical evolution and S mineral disequilibrium. By modelling a range of fluid compositions, we show that S isotope fingerprints are controlled by the ratio of oxidised to reduced S species (SO42−/H2S), and this is most strongly affected by changing temperature, fO2 and pH. We show that SO42−/H2S can change dramatically during cooling and our key insight is that S isotopes of individual sulfide or sulfate minerals can show large fractionations (up to 20 ‰) even when pH is constant and fO2 fixed to a specific mineral redox buffer. Importantly, while it is commonly assumed that SO42−/H2S is constant throughout fluid evolution, our analysis shows that this is unlikely to hold for most natural systems. We then compare our model predictions to S isotope data from porphyry and epithermal deposits, seafloor hydrothermal vents and alkaline igneous bodies. We find that our models accurately reproduce the S isotope evolution of porphyry and high sulfidation epithermal fluids, and that most require magmatic S sources between 0 and 5 ‰. The S isotopes of low sulfidation epithermal fluids and seafloor hydrothermal vents do not fit our model predictions and reflect disequilibrium between the reduced and oxidised S species and, for the latter, significant S input from seawater and biogenic sources. Alkaline igneous fluids match model predictions and confirm magmatic S sources and a wide range of temperature and redox conditions. Of all these different ore deposits, porphyry and alkaline igneous systems are particularly well-suited to S isotope investigation because they show relationships between redox, alteration and ore mineralogy that could be useful for exploration and prospecting. Ultimately, our examples demonstrate that S isotope forward models are powerful tools for identifying S sources, flagging disequilibrium processes, and validating hypotheses of magmatic fluid evolution.Publisher PDFPeer reviewe

Properties of Closed Circular DNA

A method for the measurement of the superhelix density, σ0, of a closed circular DNA from separation between fluorescent buoyant bands of nicked and closed circular forms in an ethidium bromide-CsCl equilibrium gradient is presented. Nicked and closed circular DNA's are banded together in a gradient formed by centrifuging a CsCl solution of density 1.56 gm/ml. containing 330 µg/ml ethidium bromide at 20°C for 48 hours in the preparative ultracentrifuge. The separation between the bands, normalized by the separation between the nicked and closed circular forms of a DNA of known superhelix density, is shown to be linearly related to the difference in superhelix density between the DNA's of known and unknown superhelix densities according to the equation Δσ0 = (0.115 ± 0.005)(Ωc - 1) where Δσ0 = σ0 - σ0* and Ωc = Δr/Δr* r/r (v1θ*-1)2/(v1θ-1)2 Δr is the separation between the bands, r is the average distance of the two bands from the center of rotation, θ is the buoyant density of the DNA and v1 is the partial specific volume of water. The asterisk refers to the reference DNA. A molecular weight dependence of the intercept is seen when λb2b5c DNA (molecular weight 25 x 106) is banded against a SV40 DNA (3 x 106 standard. The relationship was obtained by measuring the separations for DNA's whose superhelix densities were determined by sedimentation velocity-dye titrations. Native SV40 viral DNA with a superhelix density of -0.039 was used as a standard in all cases. DNA's with altered superhelix densities were prepared by closing nicked circular DNA's with polynucleotide ligase under various conditions. Ten closed SV40 DNA's with superhelix densities ranging from -0.007 to -0.085 have been prepared. This family of DNA's has been used to examine the effects of superhelix density on the sedimentation velocity behavior of closed SV40 DNA. The sedimentation coefficient increases as the absolute value of the superhelix density rises from a low value to 0.019, then decreases to a local minimum at 0.035 and finally increases steadily as |σ0| rises to 0.085. The sedimentation velocity-ethidium bromide titrations of these DNA's have been converted from the primary s020,* versus c data, in which s020,* is the standard sedimentation coefficient still uncorrected for the buoyant effect of bound ethidium chloride and c is the free ethidium bromide concentration, to the more meaningful s020,w versus σ0 form, with the aid of coefficients in the expression for the free energy of superhelix formation. The resultant curves form a family that is approximately superimposable on the curve for s020,w versus σ0 in the absence of ethidium bromide. The dependence of the sedimentation coefficient of selected SV40 DNA's upon ionic strength, the nature of the cation, and temperature is consistent with the previously reported effects of these variables on the rotation angle of the base pairs along the helix axis. Separations between open and closed circular DNA's in buoyant CsCl gradients containing the ethidium bromide analogue, propidium di-diodide, are shown to be 1.8 times larger than in ethidium bromide.</p

Improved orbit predictions using two-line elements

The density of orbital space debris constitutes an increasing environmental challenge. There are three ways to alleviate the problem: debris mitigation, debris removal and collision avoidance. This paper addresses collision avoidance, by describing a method that contributes to achieving a requisite increase in orbit prediction accuracy. Batch least-squares differential correction is applied to the publicly available two-line element (TLE) catalog of space objects. Using a high-precision numerical propagator, we fit an orbit to state vectors derived from successive TLEs. We then propagate the fitted orbit further forward in time. These predictions are compared to precision ephemeris data derived from the International Laser Ranging Service (ILRS) for several satellites, including objects in the congested sun-synchronous orbital region. The method leads to a predicted range error that increases at a typical rate of 100 meters per day, approximately a 10-fold improvement over TLE's propagated with their associated analytic propagator (SGP4). Corresponding improvements for debris trajectories could potentially provide initial conjunction analysis sufficiently accurate for an operationally viable collision avoidance system. We discuss additional optimization and the computational requirements for applying all-on-all conjunction analysis to the whole TLE catalog, present and near future. Finally, we outline a scheme for debris-debris collision avoidance that may become practicable given these developments.Comment: Submitted to Advances in Space Research. 13 pages, 4 figure

Optimality and limitations of audio-visual integration for cognitive systems

Multimodal integration is an important process in perceptual decision-making. In humans, this process has often been shown to be statistically optimal, or near optimal: sensory information is combined in a fashion that minimizes the average error in perceptual representation of stimuli. However, sometimes there are costs that come with the optimization, manifesting as illusory percepts. We review audio-visual facilitations and illusions that are products of multisensory integration, and the computational models that account for these phenomena. In particular, the same optimal computational model can lead to illusory percepts, and we suggest that more studies should be needed to detect and mitigate these illusions, as artifacts in artificial cognitive systems. We provide cautionary considerations when designing artificial cognitive systems with the view of avoiding such artifacts. Finally, we suggest avenues of research toward solutions to potential pitfalls in system design. We conclude that detailed understanding of multisensory integration and the mechanisms behind audio-visual illusions can benefit the design of artificial cognitive systems.Human-Robot Interactio