19 research outputs found
A Two-Phase Chemical Enrichment Model for the Milky Way Globular Cluster System
Many globular cluster systems have a distinct bimodal metallicity
distribution function (MDF) which has strikingly similar features in many large
galaxies of all types. By using the Milky Way cluster system as a typical
example, we show that bimodal MDFs can be very well matched with a double
``accreting-box'' chemical enrichment model in which both the halo (metal-poor)
and bulge (metal-rich) clusters form during an early phase of gas inflow
simultaneously with star formation. However, differences in effective yield
between the two phases are not enough by themselves to reproduce the observed
MDF shape: gas infall is required for both phases, and either the initial gas
or the infalling gas must have very different metallicities in the two separate
phases.Comment: 12 pages, 2 figures, accepted for publication in A
X-ray Point Sources in the Sombrero Galaxy: Supersoft sources, the globular cluster/LMXB connection, and an overview
We report on the population of point sources discovered during an 18.5 ksec
Chandra ACIS-S observation of the Sombrero Galaxy. We present the luminosity
function, the spectra of the 6 brightest sources, consider correlations with
globular clusters (GCs) and with planetary nebulae (PNe), and study the
galaxy's population of SSSs. We detected 122 sources, 22 of them are identified
as luminous supersoft X-ray sources (SSSs). There is an over density of SSSs
within 1.5 kpc of the nucleus, which is itself the brightest X-ray source. SSSs
are also found in the disk and halo, with 1 SSS in a globular cluster (GC).
Several sources in Sombrero's halo are good candidates for SSS models in which
the accretor is a nuclear-burning white dwarf. In total, 32 X-ray sources are
associated with GCs. The majority of sources with luminosity > 1e38 erg/s are
in GCs. These results for M104, an Sa galaxy, are similar to what has been
found for elliptical galaxies and for the late-type spiral M31. We find that
those optically bright GCs with X-ray sources house only the brightest X-ray
sources. We find that, in common with other galaxies, there appears to be a
positive connection between young (metal-rich) GCs and X-ray sources, but that
the brightest X-ray sources are equally likely to be in metal-poor GCs. We
propose a model which can explain the trends seen in the data sets from the
Sombrero and other galaxies. Thermal-time scale mass transfer can occur in some
of the the younger clusters in which the turn-off mass is slightly greater than
; multiplicity may play a role in some of the most massive
clusters; accretion from giant stars may be the dominant mechanism in some
older, less massive and less centrally concentrated clusters.Comment: 13 pages, 7 figures. ApJ submitte
Microbiological efficacy of early MRSA treatment in cystic fibrosis in a randomised controlled trial
OBJECTIVE: To evaluate microbiological effectiveness, that is, culture negativity of a non-blinded eradication protocol (Rx) compared with observation (Obs) in clinically stable cystic fibrosis participants with newly positive methicillin resistant Staphylococcusaureus (MRSA) cultures.
DESIGN: This non-blinded trial randomised participants ages 4-45 years with first or early (≤2 positive cultures within 3 years) MRSA-positive culture without MRSA-active antibiotics within 4 weeks 1:1 to Rx or Obs. The Rx protocol was: oral trimethoprim-sulfamethoxazole or if sulfa-allergic, minocycline plus oral rifampin; chlorhexidine mouthwash for 2 weeks; nasal mupirocin and chlorhexidine body wipes for 5 days and environmental decontamination for 21 days. The primary end point was MRSA culture status at day 28.
RESULTS: Between 1 April 2011 to September 2014, 45 participants (44% female, mean age 11.5 years) were randomised (24 Rx, 21 Obs). At day 28, 82% (n=18/22) of participants in the Rx arm compared with 26% (n=5/19) in the Obs arm were MRSA-negative. Adjusted for interim monitoring, this difference was 52% (95% CI 23% to 80%, p<0.001). Limiting analyses to participants who were MRSA-positive at the screening visit, 67% (8/12) in the Rx arm and 13% (2/15) in the Obs arm were MRSA-negative at day 28, adjusted difference: 49% (95% CI 22% to 71%, p<0.001). Fifty-four per cent in the Rx arm compared with 10% participants in the Obs arm remained MRSA-negative through day 84. Mild gastrointestinal side effects were higher in the Rx arm.
CONCLUSIONS: This MRSA eradication protocol for newly acquired MRSA demonstrated microbiological efficacy with a large treatment effect.
TRIAL REGISTRATION NUMBER: NCT01349192
On The Origin of the Blue Tilt in Extragalactic Globular Cluster Systems
Some early-type galaxies show a correlation between color and integrated
magnitude among the brighter metal-poor globular clusters (GCs). This
phenomenon, known as the blue tilt, implies a mass-metallicity relationship
among these clusters. In this paper we show that self-enrichment in GCs can
explain several aspects of the blue tilt, and discuss predictions of this
scenario.Comment: 25 pages, accepted to A
Stellar abundances and ages for metal-rich Milky Way globular clusters - Stellar parameters and elemental abundances for 9 HB stars in NGC6352
[ABRIDGED] Metal-rich globular clusters provide important tracers of the
formation of our Galaxy. Moreover, and not less important, they are very
important calibrators for the derivation of properties of extra-galactic
metal-rich stellar populations. Nonetheless, only a few of the metal-rich
globular clusters in the Milky Way have been studied using high-resolution
stellar spectra to derive elemental abundances. In this paper we present
elemental abundances for nine HB stars in the metal-rich globular cluster
NGC6352. The elemental abundances are based on high-resolution, high
signal-to-noise spectra obtained with VLT/UVES. The elemental abundances have
been derived using standard LTE calculations. We find that NGC6352 has [Fe/H]=
-0.55, is enhanced in the alpha-elements to about +0.2 dex for Ca, Si, and Ti
relative to Fe. For the iron-peak elements we find solar values. Based on the
spectroscopically derived stellar parameters we find that an E(B-V)=0.24 and
(m-M) roughly equal to 14.05 better fits the data than the nominal values. An
investigation of log(gf)-values for suitable FeI lines lead us to the
conclusion that the commonly used correction to the May et al.(1974) data
should not be employed. Note: only the postscript reproduces the finding chart
correctly.Comment: 24 pages (including on-line only table with all equivalent width
measurements), 12 figures, Accepted for publication in A&A. Note: only the
postscript reproduces the finding chart correctl
A comprehensive HST BVI catalogue of star clusters in five Hickson compact groups of galaxies
We present a photometric catalogue of star cluster candidates in Hickson compact groups (HCGs) 7, 31, 42, 59, and 92, based on observations with the Advanced Camera for Surveys and the Wide Field Camera 3 on the Hubble Space Telescope. The catalogue contains precise cluster positions (right ascension and declination), magnitudes, and colours in the BVI filters. The number of detected sources ranges from 2200 to 5600 per group, from which we construct the high-confidence sample by applying a number of criteria designed to reduce foreground and background contaminants. Furthermore, the high-confidence cluster candidates for each of the 16 galaxies in our sample are split into two subpopulations: one that may contain young star clusters and one that is dominated by globular older clusters. The ratio of young star cluster to globular cluster candidates varies from group to group, from equal numbers to the extreme of HCG 31 which has a ratio of 8 to 1, due to a recent starburst induced by interactions in the group. We find that the number of blue clusters with MV < −9 correlates well with the current star formation rate in an individual galaxy, while the number of globular cluster candidates with MV < −7.8 correlates well (though with large scatter) with the stellar mass. Analyses of the high-confidence sample presented in this paper show that star clusters can be successfully used to infer the gross star formation history of the host groups and therefore determine their placement in a proposed evolutionary sequence for compact galaxy groups
Improving the discomfort and satisfaction of colonoscopy by distraction with smartphones
Microbiological efficacy of early MRSA treatment in cystic fibrosis in a randomised controlled trial
http://deepblue.lib.umich.edu/bitstream/2027.42/192032/2/Microbiologic Efficacy of early MRSA treatment in cystic fibrosis in a randomized controlled trial.pdfPublished versionDescription of Microbiologic Efficacy of early MRSA treatment in cystic fibrosis in a randomized controlled trial.pdf : Published versio