Reconsidering the Effects of Local Star Formation On Type Ia Supernova Cosmology

Recent studies found a correlation with $\sim$3 sigma significance between the local star formation measured by GALEX in Type Ia supernova (SN Ia) host galaxies and the distances or dispersions derived from these SNe. We search for these effects by using data from recent cosmological analyses to greatly increase the SN Ia sample; we include 179 GALEX-imaged SN Ia hosts with distances from the JLA and Pan-STARRS SN Ia cosmology samples and 157 GALEX-imaged SN Ia hosts with distances from the Riess et al. (2011) H$_0$ measurement. We find little evidence that SNe Ia in locally star-forming environments are fainter after light curve correction than SNe Ia in locally passive environments. We find a difference of only 0.000$\pm$0.018 (stat+sys) mag for SNe fit with SALT2 and 0.029$\pm$0.027 (stat+sys) mag for SNe fit with MLCS2k2 (R$_V$ = 2.5), which suggests that proposed changes to recent measurements of H$_0$ and w are not significant and numerically smaller than the parameter measurement uncertainties. We find the greatly reduced significance of these distance modulus differences compared to Rigault et al. (2013) and Rigault et al. (2015) result from two improvements with fairly equal effects, our larger sample size and the use of JLA and Riess et al. (2011) sample selection criteria. Without these improvements, we recover the results of Rigault et al. (2015). We find that both populations have more similar dispersion in distance than found by Rigault et al. (2013), Rigault et al. (2015), and Kelly et al. (2015), with slightly smaller dispersion for locally passive SNe Ia fit with MLCS, the opposite of the effect seen by Rigault et al. (2015) and Kelly et al. (2015). We caution that measuring local SNe Ia environments in the future may require a higher-resolution instrument than GALEX and that SN sample selection has a significant effect on local star formation biases.Comment: 19 pages, 7 figures, accepted to Ap

Oblique MHD cosmic-ray modified shocks: Two-fluid numerical simulations

We present the first results of time dependent, two-fluid, cosmic-ray (CR) modified, MHD shock simulations. The calculations were carried out with a new numerical code for 1-D ideal MHD. By coupling this code with the CR energy transport equation we can simulate the time-dependent evolution of MHD shocks including the acceleration of the CR and their feedback on the shock structures. We report tests of the combined numerical method including comparisons with analytical steady state results published earlier by Webb, as well as internal consistency checks for more general MHD CR shock structures after they appear to have converged to dynamical steady states. We also present results from an initial time dependent simulation which extend the parameter space domain of previous analytical models. These new results support Webb's suggestion that equilibrium oblique shocks are less effective than parallel shocks in the acceleration of CR. However, for realistic models of anisotropic CR diffusion, oblique shocks may achieve dynamical equilibrium on shorter timescale than parallel shocks

FDA vs. Ephedra: Dietary Supplement Regulation Under DSHEA

The Dietary Supplement Health and Education Act of 1994 (DSHEA) dramatically changed the way dietary supplements are regulated in the United States. DSHEA created a new category of products defined as “dietary supplements,†and altered the way in which these products are regulated in an attempt to promote consumer access to dietary supplements. By weakening the FDA’s regulatory control of dietary supplements, DSHEA made it impossible for the FDA to insure the safety of dietary supplements sold in the United States. DSHEA allows most supplements to enter the market without first being tested for safety, and once on the market, DSHEA makes it very difficult for the FDA to remove potentially dangerous dietary supplements. The FDA’s inability to insure the safety of dietary supplements under DSHEA is exemplified by its failed efforts to place tighter restrictions on the sale of dietary supplements containing ephedra alkaloids (ephedra or ephedrine). Despite mounting evidence that supplements containing ephedra alkaloids may be responsible for serious injury and death, the well-funded and politically-connected ephedra industry has successfully fought off all FDA efforts aimed at imposing tighter regulations on ephedra supplements. Changes to existing law, including pre-market testing, mandatory reporting of adverse events, and accurate content labels are necessary if the FDA is to fulfill its goal of policing consumer safety

A Divergence-Free Upwind Code for Multidimensional Magnetohydrodynamic Flows

A description is given for preserving {\bmsy\nabla}\cdot{\vec B}=0 in a magnetohydrodynamic (MHD) code that employs the upwind, Total Variation Diminishing (TVD) scheme and the Strang-type operator splitting for multi-dimensionality. The method is based on the staggered mesh technique to constrain the transport of magnetic field: the magnetic field components are defined at grid interfaces with their advective fluxes on grid edges, while other quantities are defined at grid centers. The magnetic field at grid centers for the upwind step is calculated by interpolating the values from grid interfaces. The advective fluxes on grid edges for the magnetic field evolution are calculated from the upwind fluxes at grid interfaces. Then, the magnetic field can be maintained with {\bmsy\nabla}\cdot{\vec B}=0 exactly, if this is so initially, while the upwind scheme is used for the update of fluid quantities. The correctness of the code is demonstrated through tests comparing numerical solutions either with analytic solutions or with numerical solutions from the code using an explicit divergence-cleaning method. Also the robustness is shown through tests involving realistic astrophysical problems.Comment: 15 pages of text, 8 figures (in degraded gif format), to appear in The Astrophysical Journal (Dec. 10, 1998), original quality figures available via anonymous ftp at ftp://ftp.msi.umn.edu/pub/users/twj/mhddivb5.uu or ftp://canopus.chungnam.ac.kr/ryu/mhddivb5.u

Precessing Jets and Molecular Outflows: A 3-D Numerical Study

We present 3-D numerical hydrodynamical simulations of precessing supersonic heavy jets to explore how well they serve as a model for generating molecular outflows from Young Stellar Objects. The dynamics are studied with a number of high resolution simulations on a Cartesian grid (128x128x128 zones) using a high order finite difference method. A range of cone angles and precession rates were included in the study. Two higher resolution runs (256x256x256 zones) were made for comparison in order to confirm numerical convergence of global flow characteristics. Morphological, kinematical and dynamical characteristics of precessing jets are described and compared to important properties of straight jets and also to observations of YSOs. In order to examine the robustness of precessing jets as a mean to produce molecular outflows around Young Stellar Objects, ``synthetic observations'' of the momentum distributions of the simulated precessing jets are compared to observations of molecular outflows. It is found that precessing jets match better the morphology, highly forward driven momentum and momentum distributions along the long axis of molecular outflows than do wind-driven or straight jet-driven flow models.Comment: Accepted by ApJ, 31 pages, using aasms.sty, Also available in postscript with figures via a gzipped tar file at ftp://s1.msi.umn.edu/pub/afrank/3DJet/3DJet.tar.gz . For information contact [email protected]

The impending medical revolution in haemophilia care: one patient’s view

The history of haemophilia care has been fraught with extreme successes and epic failures. The development of plasma-derived concentrates made prophylactic treatment and home care possible, but the unintended consequences were devastating for a generation and only abated with the emergence of recombinant products. Now with the arrival of longer-acting factor concentrates and the potential offered by gene therapy, further improvements in medical and social outcomes are possible. But these new treatment approaches raise challenging ethical and moral issues that society must be prepared to confront

Nematic cells with defect-patterned alignment layers

Using Monte Carlo simulations of the Lebwohl--Lasher model we study the director ordering in a nematic cell where the top and bottom surfaces are patterned with a lattice of $\pm 1$ point topological defects of lattice spacing $a$. We find that the nematic order depends crucially on the ratio of the height of the cell $H$ to $a$. When $H/a \gtrsim 0.9$ the system is very well--ordered and the frustration induced by the lattice of defects is relieved by a network of half--integer defect lines which emerge from the point defects and hug the top and bottom surfaces of the cell. When $H/a \lesssim 0.9$ the system is disordered and the half--integer defect lines thread through the cell joining point defects on the top and bottom surfaces. We present a simple physical argument in terms of the length of the defect lines to explain these results. To facilitate eventual comparison with experimental systems we also simulate optical textures and study the switching behavior in the presence of an electric field