The Shape of Dark Matter Halos

Techniques for inferring the radial and geometric form of dark matter halos and the results they have produced to date are reviewed. Dark halos appear to extend to at least ~50 kpc with total enclosed masses that rise linearly with radius R. Whether this behavior can be extrapolated to distances as large as 200 kpc and beyond is controversial; results at this radius are model-dependent. Observationally, the geometrical form of the dark halo can be characterized by the equatorial axis ratio b/a (ovalness) and vertical-to-equatorial axis ratio c/a (flattening) of the total density. Different techniques consistently yield b/a > 0.7 (and thus b/a > 0.9 for the potential) at R~20 kpc, with more axisymmetric values, b/a >~ 0.8, being more likely. Results are less consistent for the vertical flattening, perhaps due to the difference in the spatial regions probed by different techniques or inappropriate assumptions. Techniques that probe furthest from the stellar plane z~15 kpc consistently implicate substantially flattened c/a = 0.5 +/- 0.2 dark halos. These axis ratios are in acceptable agreement with expectations from N-body simulations of cold dark matter mixed with ~10% dissipational gas.Comment: Invited Review to appear in Galaxy Dynamics, 1999, eds. D. Merritt, J.A. Sellwood and M. Valluri, ASP, LaTex using paspconf.sty, 3 figures in 5 postscript file

Planetary Microlensing: Present Status and Long-term Goals

Massive gravitational microlensing programs were begun about a decade ago as a means to search for compact baryonic dark matter in the Galaxy, but before the first events were detected the technique was also proposed as a means of detecting extra-solar planets in our Galaxy. Current microlensing planet searches, which have been underway for four years, are sensitive to jovian-mass planets orbiting a few to several AU from their parent Galactic stars. Within two years, sufficient data should be in hand to characterize or meaningfully constrain the frequency of massive planets in this range of parameter space, nicely complementing information about planets at smaller orbital radii now being provided by radial velocity searches. In principle, the technique could be pushed to smaller planetary masses, but only if a larger number of faint microlensed sources can be monitored with higher precision and temporal sampling. The VST on Paranal, with spectroscopic follow-up with the VLT, may be the ideal instrument for such an ambitious program.Comment: Invited Review at VLT Opening Symposium, Antofagasta, Chile, March 1999. To appear in the Springer-Verlag series ``ESO Astrophysics Symposia'

Another Flattened Dark Halo: Plar Ring Galaxy A0136-0801

Knowledge of the shape of dark matter halos is critical to our understanding of galaxy formation, dynamics, and of the nature of dark matter itself. Polar ring galaxies (PRGs) --- early-type galaxies defined by their outer rings of gas, dust and stars on orbits nearly perpendicular to those of the central host --- provide a rare probe of the vertical-to-radial axis ratio $(q_{\rho} = c/a)$ of dark halos. We present a Fabry-Perot velocity field for the H$\alpha$ gas in the kinematically-confirmed PRG \gal. By comparing ring orbits evolved in a generalized mass model to the observed ring velocity field and morphology of \gal, we conclude that $q_\rho \sim 0.5$ and rule out a spherical geometry.Comment: uuencoded gz-compressed file with figures include

WFIRST Ultra-Precise Astrometry II: Asteroseismology

WFIRST microlensing observations will return high-precision parallaxes, sigma(pi) < 0.3 microarcsec, for the roughly 1 million stars with H<14 in its 2.8 deg^2 field toward the Galactic bulge. Combined with its 40,000 epochs of high precision photometry (~0.7 mmag at H_vega=14 and ~0.1 mmag at H=8), this will yield a wealth of asteroseismic data of giant stars, primarily in the Galactic bulge but including a substantial fraction of disk stars at all Galactocentric radii interior to the Sun. For brighter stars, the astrometric data will yield an external check on the radii derived from the two asteroseismic parameters, and nu_max, while for the fainter ones, it will enable a mass measurement from the single measurable asteroseismic parameter nu_max. Simulations based on Kepler data indicate that WFIRST will be capable of detecting oscillations in stars from slightly less luminous than the red clump to the tip of the red giant branch, yielding roughly 1 million detections.Comment: 13 pages, 6 figures, submitted to JKA

The Sulzer Hip Replacement Recall Crisis: A Patient\u27s Perspective

This case discusses a product recall that resulted from a manufacturing defect and the degree to which the company distributed accurate and timely information to affected patients. More specifically, the case examines the crisis communication of Sulzer Orthopedics and its efforts to negotiate the interests of various stakeholders, while limiting liability. Written from the perspective of a patient, the case raises interesting questions regarding organizational duties related to product liability. It also provides valuable insights into how organizational communication may have both short- and long-term effects on its relationship with patients and physicians, among others

A postal survey to identify and describe nurse led clinics in genitourinary medicine services across England

Background: Nurses in genitourinary medicine (GUM) services are progressively extending their roles to conduct "comprehensive care" nurse led clinics. In such roles the nurse coordinates the first line, comprehensive care of patients presenting with sexual health conditions and issues. Objectives: To identify and describe comprehensive care nurse led clinics in GUM services across England. Methods: A postal questionnaire consisting of 17 closed response questions was sent to 209 GUM services across England. A second questionnaire was sent to non-responders to increase the response rate. Data were single entered and analysed using SPSS. Results: Of the 190 GUM clinic respondents (91% response rate), 44 (23%) reported providing some form of comprehensive care nurse led clinic, 90% of which were initiated since 1995. Key results show staff development featured as the main reason for initiating such services and there was general consistency in the aspects of care undertaken by these nurses. There was evidence of guideline development specific to nurse led care and some patient group direction use for supplying medication. The level of support from medical staff while nurse led clinics were being conducted varied between services. Few services have conducted any audit or research to monitor/evaluate nurse led care. There was little consistency in the clinical experience and educational prerequisites to undertake comprehensive care nurse led clinics. Continuing professional development opportunities also varied between services. Conclusions: The steady growth of comprehensive care nurse led clinics indicates that the skills of GUM nurses are being recognised. Nurses working in advanced practice roles now require courses and study days reflecting these changes in practice. Locally agreed practice guidelines can define nursing practice boundaries and ensure accountability, as will the development of patient group directions to supply medication. Monitoring and evaluation of nurse led clinics also require attention