ROSAT Evidence for Intrinsic Oxygen Absorption in Cooling Flow Galaxies and Groups

Using spatially resolved, deprojected ROSAT PSPC spectra of 10 of the brightest cooling flow galaxies and groups with low Galactic column densities we have detected intrinsic absorption over energies ~0.4-0.8 keV in half of the sample. Since no intrinsic absorption is indicated for energies below ~0.4 keV, the most reasonable model for the absorber is collisionally ionized gas at temperatures T=10^{5-6} K with most of the absorption arising from ionized states of oxygen but with a significant contribution from carbon and nitrogen. The soft X-ray emission of this warm gas can explain the sub-Galactic column densities of cold gas inferred within the central regions of most of the systems. Attributing the absorption to ionized gas reconciles the large columns of cold H and He inferred from EINSTEIN and ASCA with the lack of such columns inferred from ROSAT. Within the central ~10-20 kpc, where the constraints are most secure, the estimated mass of the ionized absorber is consistent with most (perhaps all) of the matter deposited by a cooling flow over the lifetime of the flow. Since the warm absorber produces no significant H or He absorption the large absorber masses are consistent with the negligible atomic and molecular H inferred from HI and CO observations of cooling flows. It is also found that if T > ~2x10^5 K then the optical and UV emission implied by the warm gas does not violate published constraints. Finally, we discuss how the prediction of warm ionized gas as the product of mass drop-out in these and other cooling flows can be verified with new CHANDRA and XMM observations. (Abridged)Comment: 17 pages (5 figures), Accepted for publication in ApJ, expanded discussion of multiphase spectral models, theoretical implications of warm gas in cooling flows, and the statistical significance of the oxygen absorptio

The Extended Blue Continuum and Line Emission around the Central Radio Galaxy in Abell 2597

We present results from detailed imaging of the centrally dominant radio elliptical galaxy in the cooling flow cluster Abell 2597, using data obtained with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). This object is one of the archetypal "blue-lobed" cooling flow radio elliptical galaxies, also displaying a luminous emission-line nebula, a compact radio source, and a significant dust lane and evidence of molecular gas in its center. We show that the radio source is surrounded by a complex network of emission-line filaments, some of which display a close spatial association with the outer boundary of the radio lobes. We present a detailed analysis of the physical properties of ionized and neutral gas associated with the radio lobes, and show that their properties are strongly suggestive of direct interactions between the radio plasma and ambient gas. We resolve the blue continuum emission into a series of knots and clumps, and present evidence that these are most likely due to regions of recent star formation. We investigate several possible triggering mechanisms for the star formation, including direct interactions with the radio source, filaments condensing from the cooling flow, or the result of an interaction with a gas-rich galaxy, which may also have been responsible for fueling the active nucleus. We propose that the properties of the source are plausibly explained in terms of accretion of gas by the cD during an interaction with a gas-rich galaxy, which combined with the fact that this object is located at the center of a dense, high-pressure ICM can account for the high rates of star formation and the strong confinement of the radio source.Comment: Astrophysical Journal, in press, 34 pages, includes 6 PostScript figures. Latex format, uses aaspp4.sty and epsf.sty file

On the Internal Absorption of Galaxy Clusters

A study of the cores of galaxy clusters with the Einstein SSS indicated the presence of absorbing material corresponding to 1E+12 Msun of cold cluster gas, possibly resulting from cooling flows. Since this amount of cold gas is not confirmed by observations at other wavelengths, we examined whether this excess absorption is present in the ROSAT PSPC observations of 20 bright galaxy clusters. For 3/4 of the clusters, successful spectral fits were obtained with absorption due only to the Galaxy, and therefore no extra absorption is needed within the clusters, in disagreement with the results from the Einstein SSS data for some of the same clusters. For 1/4 of the clusters, none of our spectral fits was acceptable, suggesting a more complicated cluster medium than the two-temperature and cooling flow models considered here. However, even for these clusters, substantial excess absorption is not indicated.Comment: accepted by the Astrophysical Journa

Formation of Low Mass Stars in Elliptical Galaxy Cooling Flows

X-ray emission from hot (T = 10^7 K) interstellar gas in massive elliptical galaxies indicates that 10^{10} M_sun has cooled over a Hubble time, but optical and radio evidence for this cold gas is lacking. We provide detailed theoretical support for the hypothesis that this gas has formed into low luminosity stars. Within several kpc of the galactic center, interstellar gas first cools to T = 10^4 K where it is heated by stellar UV and emits the observed diffuse optical line emission. This cooling occurs at a large number (10^6) of isolated sites. After less than a solar mass of gas has accumulated (10^{-6} M_sun/yr) at a typical cooling site, a neutral (HI or H_2) core develops in the HII cloud where gas temperatures drop to T = 15 K and the ionization level (from thermal X-rays) is very low (x = 10^{-6}). We show that the maximum mass of cores that become gravitationally unstable is only about 2 M_sun. No star can exceed this mass. Fragmentation of collapsing cores produces a population of low mass stars with a bottom-heavy IMF and radial orbits. Gravitational collapse and ambipolar diffusion are rapid. The total mass of star-forming (dust-free) HI or H_2 cores in a typical bright elliptical is only 10^6 M_sun, below current observational thresholds.Comment: 23 pages in AASTEX LaTeX with 8 figures; accepted by Astrophysical Journa

Long-Term Survival after Gamma Knife Radiosurgery in a Case of Recurrent Glioblastoma Multiforme: A Case Report and Review of the Literature

The management of recurrent glioblastoma is highly challenging, and treatment outcomes remain uniformly poor. Glioblastoma is a highly infiltrative tumor, and complete surgical resection of all microscopic extensions cannot be achieved at the time of initial diagnosis, and hence local recurrence is observed in most patients. Gamma Knife radiosurgery has been used to treat these tumor recurrences for select cases and has been successful in prolonging the median survival by 8–12 months on average for select cases. We present the unique case of a 63-year-old male with multiple sequential recurrences of glioblastoma after initial standard treatment with surgery followed by concomitant external beam radiation therapy and chemotherapy (temozolomide). The patient was followed clinically as well as with surveillance MRI scans at every 2-3-month intervals. The patient underwent Gamma Knife radiosurgery three times for 3 separate tumor recurrences, and the patient survived for seven years following the initial diagnosis with this aggressive treatment. The median survival in patients with recurrent glioblastoma is usually 8–12 months after recurrence, and this unique case illustrates that aggressive local therapy can lead to long-term survivors in select situations. We advocate that each patient treatment at the time of recurrence should be tailored to each clinical situation and desire for quality of life and improved longevity

IFN-γ, IL-4 and IL-13 modulate responsiveness of human airway smooth muscle cells to IL-13

© 2008 Moynihan et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Telehealth interventions to support self-management of long-term conditions: a systematic meta-review of diabetes, heart failure, asthma, chronic obstructive pulmonary disease and cancer.

Background: Self-management support is one mechanism by which telehealth interventions have been proposed to facilitate management of long-term conditions. Objective: The objectives of this metareview were to (1) assess the impact of telehealth interventions to support self-management on disease control and health care utilization, and (2) identify components of telehealth support and their impact on disease control and the process of self-management. Our goal was to synthesise evidence for telehealth-supported self-management of diabetes (types 1 and 2), heart failure, asthma, chronic obstructive pulmonary disease (COPD) and cancer to identify components of effective self-management support. Methods: We performed a metareview (a systematic review of systematic reviews) of randomized controlled trials (RCTs) of telehealth interventions to support self-management in 6 exemplar long-term conditions. We searched 7 databases for reviews published from January 2000 to May 2016 and screened identified studies against eligibility criteria. We weighted reviews by quality (revised A Measurement Tool to Assess Systematic Reviews), size, and relevance. We then combined our results in a narrative synthesis and using harvest plots. Results: We included 53 systematic reviews, comprising 232 unique RCTs. Reviews concerned diabetes (type 1: n=6; type 2, n=11; mixed, n=19), heart failure (n=9), asthma (n=8), COPD (n=8), and cancer (n=3). Findings varied between and within disease areas. The highest-weighted reviews showed that blood glucose telemonitoring with feedback and some educational and lifestyle interventions improved glycemic control in type 2, but not type 1, diabetes, and that telemonitoring and telephone interventions reduced mortality and hospital admissions in heart failure, but these findings were not consistent in all reviews. Results for the other conditions were mixed, although no reviews showed evidence of harm. Analysis of the mediating role of self-management, and of components of successful interventions, was limited and inconclusive. More intensive and multifaceted interventions were associated with greater improvements in diabetes, heart failure, and asthma. Conclusions: While telehealth-mediated self-management was not consistently superior to usual care, none of the reviews reported any negative effects, suggesting that telehealth is a safe option for delivery of self-management support, particularly in conditions such as heart failure and type 2 diabetes, where the evidence base is more developed. Larger-scale trials of telehealth-supported self-management, based on explicit self-management theory, are needed before the extent to which telehealth technologies may be harnessed to support self-management can be established

Keeping the Board in the Dark: CEO Compensation and Entrenchment

We study a model in which a CEO can entrench himself by hiding information from the board that would allow the board to conclude that he should be replaced. Assuming that even diligent monitoring by the board cannot fully overcome the information asymmetry visà- vis the CEO, we ask if there is a role for CEO compensation to mitigate the inefficiency. Our analysis points to a novel argument for high-powered, non-linear CEO compensation such as bonus pay or stock options. By shifting the CEO’s compensation into states where the firm’s value is highest, a high-powered compensation scheme makes it as unattractive as possible for the CEO to entrench himself when he expects that the firm’s future value under his management and strategy is low. This, in turn, minimizes the severance pay needed to induce the CEO not to entrench himself, thereby minimizing the CEO’s informational rents. Amongst other things, our model suggests how deregulation and technological changes in the 1980s and 1990s might have contributed to the rise in CEO pay and turnover over the same period