Triggered massive-star formation on the borders of Galactic HII regions. II. Evidence for the collect and collapse process around RCW 79

We present SEST-SIMBA 1.2-mm continuum maps and ESO-NTT SOFI JHK images of the Galactic HII region RCW 79. The millimetre continuum data reveal the presence of massive fragments located in a dust emission ring surrounding the ionized gas. The two most massive fragments are diametrically opposite each other in the ring. The near-IR data, centred on the compact HII region located at the south-eastern border of RCW 79, show the presence of an IR-bright cluster containing massive stars along with young stellar objects with near-IR excesses. A bright near- and mid-IR source is detected towards maser emissions, 1.2 pc north-east of the compact HII region centre. Additional information, extracted from the Spitzer GLIMPSE survey, are used to discuss the nature of the bright IR sources observed towards RCW 79. Twelve luminous Class I sources are identified towards the most massive millimetre fragments. All these facts strongly indicate that the massive-star formation observed at the border of the HII region RCW 79 has been triggered by its expansion, most probably by the collect and collapse process.Comment: 14 pages, 15 figures. Accepted for publication in A&A. The images have been highly compressed for astro-ph. A version of this paper with higher-resolution figures is available at http://www.oamp.fr/matiere/rcw79.pd

Triggered massive-star formation on the borders of Galactic HII regions. III. Star formation at the periphery of Sh2-219

Context. Massive-star formation triggered by the expansion of HII regions. Aims. To understand if sequential star formation is taking place at the periphery of the HII region Sh2-219. Methods. We present 12CO(2-1) line observations of this region, obtained at the IRAM 30-m telescope (Pico Veleta, Spain). Results. In the optical, Sh2-219 is spherically symmetric around its exciting star; furthermore it is surrounded along three quarters of its periphery by a ring of atomic hydrogen. This spherical symmetry breaks down at infrared and millimetre wavelengths. A molecular cloud of about 2000\msol lies at the southwestern border of Sh2-219, in the HI gap. Two molecular condensations, elongated along the ionization front, probably result from the interaction between the expanding HII region and the molecular cloud. In this region of interaction there lies a cluster containing many highly reddened stars, as well as a massive star exciting an ultracompact HII region. More surprisingly, the brightest parts of the molecular cloud form a `chimney', perpendicular to the ionization front. This chimney is closed at its south-west extremity by H-alpha walls, thus forming a cavity. The whole structure is 7.5 pc long. A luminous H-alpha emission-line star, lying at one end of the chimney near the ionization front, may be responsible for this structure. Confrontation of the observations with models of HII region evolution shows that Sh2-219 is probably 10^5 yr old. The age and origin of the near-IR cluster observed on the border of Sh2-219 remain unknown.Comment: 11 pages, 10 figures. To be published in A&

Solid-Organ Transplantation in HIV-Infected Patients

Before the introduction of highly active antiretroviral therapy in the mid-1990s, transplantation centers were understandably reluctant to provide scarce solid organs for patients infected with the human immunodeficiency virus (HIV). However, because treated patients can now expect to live substantially longer than before, many will have end-stage organ disease long before they have life-threatening conditions related to HIV infection. It is therefore time for the transplantation community to readdress the safety, efficacy, and propriety of transplanting scarce organs in HIV-positive patients who need them. In this article, we provide ethical arguments for viewing transplantation in patients with HIV infection as analogous to transplantation in patients with other chronic illnesses. Accordingly, transplantation in HIV-positive patients should be initiated at major centers and should not be considered experimental. In addition, reimbursement for such procedures should be similar to that for transplantation in other patients, unless evidence accumulates that HIV-infected transplant recipients fare poorly

Iron oxidation at low temperature (260–500 C) in air and the effect of water vapor

The oxidation of iron has been studied at low temperatures (between 260 and 500 C) in dry air or air with 2 vol% H2O, in the framework of research on dry corrosion of nuclear waste containers during long-term interim storage. Pure iron is regarded as a model material for low-alloyed steel. Oxidation tests were performed in a thermobalance (up to 250 h) or in a laboratory furnace (up to 1000 h). The oxide scales formed were characterized using SEM-EDX, TEM, XRD, SIMS and EBSD techniques. The parabolic rate constants deduced from microbalance experiments were found to be in good agreement with the few existing values of the literature. The presence of water vapor in air was found to strongly influence the transitory stages of the kinetics. The entire structure of the oxide scale was composed of an internal duplex magnetite scale made of columnar grains and an external hematite scale made of equiaxed grains. 18O tracer experiments performed at 400 C allowed to propose a growth mechanism of the scale

Mortality Differences Between Traditional Medicare and Medicare Advantage: A Risk-Adjusted Assessment Using Claims Data.

Medicare Advantage (MA) has grown rapidly since the Affordable Care Act; nearly one-third of Medicare beneficiaries now choose MA. An assessment of the comparative value of the 2 options is confounded by an apparent selection bias favoring MA, as reflected in mortality differences. Previous assessments have been hampered by lack of access to claims diagnosis data for the MA population. An indirect comparison of mortality as an outcome variable was conducted by modeling mortality on a traditional fee-for-service (FFS) Medicare data set, applying the model to an MA data set, and then evaluating the ratio of actual-to-predicted mortality in the MA data set. The mortality model adjusted for clinical conditions and demographic factors. Model development considered the effect of potentially greater coding intensity in the MA population. Further analysis calculated ratios for subpopulations. Predicted, risk-adjusted mortality was lower in the MA population than in FFS Medicare. However, the ratio of actual-to-predicted mortality (0.80) suggested that the individuals in the MA data set were less likely to die than would be predicted had those individuals been enrolled in FFS Medicare. Differences between actual and predicted mortality were particularly pronounced in low income (dual eligibility), nonwhite race, high morbidity, and Health Maintenance Organization (HMO) subgroups. After controlling for baseline clinical risk as represented by claims diagnosis data, mortality differences favoring MA over FFS Medicare persisted, particularly in vulnerable subgroups and HMO plans. These findings suggest that differences in morbidity do not fully explain differences in mortality between the 2 programs

Virgin River multi-objective optimization: maximizing endangered fish habitat and minimizing costs

This paper discusses a comparative analysis of hypothetical operational scenarios by the use of dynamic temperature and fish habitat modelling in a multi-objective framework in the Virgin River Basin, Utah. Results were compared on the basis of quantified fish habitat, operational costs, and hydropower revenue. The modelling framework, the Virgin River Operation Optimization Model, is considered as a basin-level planning model. The optimization objectives were to minimize net river system operational cost of the Washington County Water Conservation District and maximize endangered fish habitat. Considerations included infrastructure alternatives to increase flow and cold water discharges as well as demand reductions. Given the nature of the problem, an optimization procedure was developed to approximate a Pareto front or trade-off surface for the two management objectives. This trade-off surface approximation is desired to help users compare the merits of any particular solution. The relative differences between alternatives elucidated sensitivities to the system responses along the approximated Pareto front. Limitations to the methods are discussed and recommendations for future work are provided

Diffuse Ionized Gas in the Dwarf Irregular Galaxy DDO 53

The spectral characteristics throughout the dwarf irregular galaxy DDO 53 are studied. The results are very similar to those for other irregular galaxies: high excitation and low values of the [SII]/Halpha ratio. The most likely ionization source is photon leakage from the classical HII regions, without any other source, although the interstellar medium of the galaxy is quite perturbed. Moreover, the physical conditions throughout the galaxy do not change very much because both the photon leakage percentage and the ionization temperature are very similar. In addition, the determined metal content for two HII regions indicates that DDO 53 is a low-metallicity galaxy.Comment: 32 pages, 9 figures, 7 tables. AJ, in pres