The Detection of a Cooling Flow Elliptical Galaxy from OVI Emission

Cooling flow models for the hot gas in elliptical galaxies predict that gas is cooling at a rate of ~ 1 solar mass/yr, yet there is little evidence for this phenomenon beyond the X-ray waveband. If hot gas is cooling, it will pass through the 3x10^5 K regime and radiate in the OVI 1032,1038 ultraviolet lines, which can be detected with the Far Ultraviolet Spectroscopic Explorer (FUSE) and here we report on FUSE observations of the X-ray bright early-type galaxies NGC 1404 and NGC 4636. In NGC 1404, the OVI doublet is not detected, implying a cooling rate < 0.3 solar masses/yr, which is below the predicted values from the cooling flow model of 0.4-0.9 solar masses/yr. In NGC 4636, both OVI lines are clearly detected, indicating a cooling rate of 0.43 +/- 0.06 solar masses/yr, which falls within the range of values from the cooling flow prediction, 0.36-2.3 solar masses/yr and is closest to the model where the production of the cooled gas is distributed through the galaxy. The emission line widths, 44 +/- 15 km/s, are close to the Doppler broadening value (30 km/s), indicating that the flow is quiescent rather than turbulent, and that the flow velocity is < 30 km/s.Comment: to be published in ApJ Letters; 8 Latex pages with 2 embedded figure

Transient social-ecological stability: The effects of invasive species and ecosystem restoration on nutrient management compromise in lake erie

Together, lake ecosystems and local human activity form complex social-ecological systems (SESs) characterized by feedback loops and discontinuous change. Researchers in diverse fields have suggested that complex systems do not have single stable equilibria in the long term because of inevitable perturbation. During this study, we sought to address the general question of whether or not stable social-ecological equilibria exist in highly stressed and managed lacustrine systems. Using an integrated human-biophysical model, we investigated the impacts of a species invasion and ecosystem restoration on SES equilibrium, defined here as a compromise in phosphorus management among opposing stakeholders, in western Lake Erie. Our integrated model is composed of a calibrated ecological submodel representing Sandusky Bay, and a phosphorus management submodel that reflects the societal benefits and costs of phosphorus regulation. These two submodels together form a dynamic feedback loop that includes freshwater ecology, ecosystem services, and phosphorus management. We found that the invasion of dreissenid mussels decreased ecosystem resistance to eutrophication, necessitating increased phosphorus management to preserve ecosystem services and thus creating the potential for a shift in social-ecological equilibrium. Additionally, our results suggest that net benefits in the region following the invasion of dreissenids may never again reach the pre-invasion level if on-site phosphorus control is the sole management lever. Further demonstrating transient system stability, large-scale wetland restoration shifted points of management compromise to states characterized by less on-site phosphorus management and higher environmental quality, resulting in a significant increase in net benefits in the region. We conclude that lacustrine SESs are open and dynamic, and we recommend that future models of these systems emphasize site-specific perturbation over equilibrium, thereby aiding the development of management plans for building system resistance to undesirable change that are both flexible and sustainable in an unknowable future. © 2010 by the author(s)

A New Method for Searching for Free Fractional Charge Particles in Bulk Matter

We present a new experimental method for searching for free fractional charge in bulk matter; this new method derives from the traditional Millikan liquid drop method, but allows the use of much larger drops, 20 to 100 mm in diameter, compared to the traditional method that uses drops less than 15 mm in diameter. These larger drops provide the substantial advantage that it is then much easier to consistently generate drops containing liquid suspensions of powdered meteorites and other special minerals. These materials are of great importance in bulk searches for fractional charge particles that may have been produced in the early universe.Comment: 17 pages, 5 figures in a singl PDF file (created from WORD Doc.). Submitted to Review of Scientific Instrument

Primordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results

Upcoming precision measurements of the temperature anisotropy of the cosmic microwave background (CMB) at high multipoles will need to be complemented by a more complete understanding of recombination, which determines the damping of anisotropies on these scales. This is the third in a series of papers describing an accurate theory of HeI and HeII recombination. Here we describe the effect of Thomson scattering, the $^3$He isotope shift, the contribution of rare decays, collisional processes, and peculiar motion. These effects are found to be negligible: Thomson and $^3$He scattering modify the free electron fraction $x_e$ at the level of several $\times 10^{-4}$. The uncertainty in the $2^3P^o-1^1S$ rate is significant, and for conservative estimates gives uncertainties in $x_e$ of order $10^{-3}$. We describe several convergence tests for the atomic level code and its inputs, derive an overall $C_\ell$ error budget, and relate shifts in $x_e(z)$ to the changes in $C_\ell$, which are at the level of 0.5% at $\ell =3000$. Finally, we summarize the main corrections developed thus far. The remaining uncertainty from known effects is $\sim 0.3$ in $x_e$.Comment: 19 pages, 15 figures, to be submitted to PR

An implantable carotid sinus stimulator for drug-resistant hypertension: Surgical technique and short-term outcome from the multicenter phase II Rheos feasibility trial

BackgroundA large number of patients have hypertension that is resistant to currently available pharmacologic therapy. Electrical stimulation of the carotid sinus baroreflex system has been shown to produce significant chronic blood pressure decreases in animals. The phase II Rheos Feasibility Trial was performed to assess the response of patients with multidrug-resistant hypertension to such stimulation.MethodsThe system consists of an implantable pulse generator with bilateral perivascular carotid sinus leads. Implantation is performed bilaterally with patients under narcotic anesthesia (to preserve the reflex for assessment of optimal lead placement). Dose-response testing at 0 to 6 V is assessed before discharge and at monthly intervals thereafter; the device is activated after 1 month’s recovery time. This was a Food and Drug Administration–monitored phase II trial performed at five centers in the United States.ResultsTen patients with resistant hypertension (taking a median of six antihypertensive medications) underwent implantation. All 10 were successful, with no significant morbidity. The mean procedure time was 198 minutes. There were no adverse events attributable to the device. Predischarge dose-response testing revealed consistent (r = .88) reductions in systolic blood pressure of 41 mm Hg (mean fall is from 180-139 mm Hg), with a peak response at 4.8 V (P < .001) and without significant bradycardia or bothersome symptoms.ConclusionsA surgically implantable device for electrical stimulation of the carotid baroreflex system can be placed safely and produces a significant acute decrease in blood pressure without significant side effects

OVI in Elliptical Galaxies: Indicators of Cooling Flows

Early-type galaxies often contain a hot X-ray emitting interstellar medium (3-8E6 K) with an apparent radiative cooling time much less than a Hubble time. If unopposed by a heating mechanism, the gas will radiatively cool to temperatures <= 10E4 K at a rate proportional to L_X/T_X, typically 0.03-1 M_solar yr^-1. We can test if gas is cooling through the 3E5 K range by observing the OVI doublet, whose luminosity is proportional to the cooling rate. Here we report on a study of an unbiased sample of 24 galaxies, obtaining Far Ultraviolet Spectroscopic Explorer spectra to complement the X-ray data of ROSAT} and Chandra. The OVI line emission was detected in about 40% of the galaxies and at a luminosity level similar to the prediction from the cooling flow model. There is a correlation between Mdot_OVI and Mdot_X, although there is significant dispersion about the relationship, where the OVI is brighter or dimmer than expected by a factor of three or more. If the cooling flow picture is to be retained, this dispersion requires that cooling flows be time-dependent, as might occur by the activity of an AGN. However, of detected objects, those with the highest or lowest values of Mdot_OVI/Mdot_X are not systematically hot or cool, as one might predict from AGN heating.Comment: 49 pages, 26 figures, ApJ, in pres

Comparison of 3-Factor Prothrombin Complex Concentrate and Low-Dose Recombinant Factor VIIa for Warfarin Reversal

INTRODUCTION: Prothrombin complex concentrate (PCC) and recombinant Factor VIIa (rFVIIa) have been used for emergent reversal of warfarin anticoagulation. Few clinical studies have compared these agents in warfarin reversal. We compared warfarin reversal in patients who received either 3 factor PCC (PCC3) or low-dose rFVIIa (LDrFVIIa) for reversal of warfarin anticoagulation. METHODS: Data were collected from medical charts of patients who received at least one dose of PCC3 (20 units/kg) or LDrFVIIa (1000 or 1200 mcg) for emergent warfarin reversal from August 2007 to October 2011. The primary end-points were achievement of an INR 1.5 or less for efficacy and thromboembolic events for safety. RESULTS: Seventy-four PCC3 and 32 LDrFVIIa patients were analyzed. Baseline demographics, reason for warfarin reversal, and initial INR were equivalent. There was no difference in the use of vitamin K or fresh frozen plasma. More LDrFVIIa patients achieved an INR of 1.5 or less (71.9% vs. 33.8%, p =0.001). The follow-up INR was lower after LDrFVIIa (1.25 vs. 1.75, p < 0.05) and the percent change in INR was larger after LDrFVIIa (54.1% vs. 38.8%, p = 0.002). There was no difference in the number of thromboembolic events (2 LDrFVIIa vs. 5 PCC3, p = 1.00), mortality, length of hospital stay, or cost. CONCLUSIONS: Based on achieving a goal INR of 1.5 or less, LDrFVIIa was more likely than PCC3 to reverse warfarin anticoagulation. Thromboembolic events were equivalent in patients receiving PCC3 and LDrFVIIa

OVI Observations of Galaxy Clusters: Evidence for Modest Cooling Flows

A prediction of the galaxy cluster cooling flow model is that as gas cools from the ambient cluster temperature, emission lines are produced in gas at subsequently decreasing temperatures. Gas passing through 10^5.5 K emits in the lines of OVI 1032,1035, and here we report a FUSE study of these lines in three cooling flow clusters, Abell 426, Abell 1795, and AWM 7. No emission was detected from AWM 7, but OVI is detected from the centers of Abell 426 and Abell 1795, and possibly to the south of the center in Abell 1795, where X-ray and optical emission line filaments lie. In Abell 426, these line luminosities imply a cooling rate of 32+/-6 Msolar/yr within the central r = 6.2 kpc region, while for Abell 1795, the central cooling rate is 26+/-7 Msolar/yr (within r = 22 kpc), and about 42+/-9 Msolar/yr including the southern pointing. Including other studies, three of six clusters have OVI emission, and they also have star formation as well as emission lines from 1E4 K gas. These observations are generally consistent with the cooling flow model but at a rate closer to 30 Msolar/yr than originally suggested values of 100-1000 Msolar/yr.Comment: 17 pages, 6 figures, ApJ, in pres

The Structural Evolution of Substructure

We investigate the evolution of substructure in cold dark matter halos using N-body simulations of tidal stripping of substructure halos (subhalos) within a static host potential. We find that halos modeled following the Navarro, Frenk & White (NFW) mass profile lose mass continuously due to tides from the massive host, leading to the total disruption of satellite halos with small tidal radii. The structure of stripped NFW halos depends mainly on the fraction of mass lost, and can be expressed in terms of a simple correction to the original NFW profile. We apply these results to substructure in the Milky Way, and conclude that the dark matter halos surrounding its dwarf spheroidal (dSph) satellites have circular velocity curves that peak well beyond the luminous radius at velocities significantly higher than expected from the stellar velocity dispersion. Our modeling suggests that the true tidal radii of dSphs lie well beyond the putative tidal cutoff observed in the surface brightness profile, suggesting that the latter are not really tidal in origin but rather features in the light profile of limited dynamical relevance. For Draco, in particular, our modeling implies that its tidal radius is much larger than derived by Irwin & Hatzidimitriou (1995), lending support to the interpretation of recent Sloan survey data by Odenkirchen et al. (2001). Similarly, our model suggests that Carina's halo has a peak circular velocity of ~55 km/s, which may help explain how this small galaxy has managed to retain enough gas to undergo several bursts of star formation. Our results imply a close correspondence between the most massive subhalos expected in a CDM universe and the known satellites of the Milky Way, and suggest that only subhalos with peak circular velocities below 35 km/s lack readily detectable luminous counterparts.Comment: 28 pages, 14 figures; accepted for publication in the Astrophysical Journa