58 research outputs found
The ultraviolet signature of massive stars in starburst galaxies
Studies in different spectral regimes of starburst galaxies clearly indicate the presence of hot, massive stars. However, only the UV spectral region can be used to directly identify the spectroscopic signature of these stars. The typical contributor to the integrated continuum at approximately 1400 A of a starburst is from the hot B stars. More massive stars are responsible for the majority to the UV lines which are broad photospheric absorption lines and wind emission or P Cygni profiles. We present a progress report of a study of the massive star population in starburst galaxies using the UV spectral region
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Lung Injury Prediction Score for the Emergency Department: First Step Towards Prevention in Patients at Risk
Background: Early identification of patients at risk of developing acute lung injury (ALI) is critical for potential preventive strategies. We aimed to derive and validate an acute lung injury prediction score (EDLIPS) in a multicenter sample of emergency department (ED) patients. Methods: We performed a subgroup analysis of 4,361 ED patients enrolled in the previously reported multicenter observational study. ED risk factors and conditions associated with subsequent ALI development were identified and included in the EDLIPS model. Scores were derived and validated using logistic regression analyses. The model was assessed with the area under the receiver-operating curve (AUC) and compared to the original LIPS model (derived from a population of elective high-risk surgical and ED patients) and the Acute Physiology and Chronic Health Evaluation (APACHE II) score. Results: The incidence of ALI was 7.0% (303/4361). EDLIPS discriminated patients who developed ALI from those who did not with an AUC of 0.78 (95% CI 0.75, 0.82), better than the APACHE II AUC 0.70 (p ≤ 0.001) and similar to the original LIPS score AUC 0.80 (p = 0.07). At an EDLIPS cutoff of 5 (range −0.5, 15) positive and negative likelihood ratios (95% CI) for ALI development were 2.74 (2.43, 3.07) and 0.39 (0.30, 0.49), respectively, with a sensitivity 0.72(0.64, 0.78), specificity 0.74 (0.72, 0.76), and positive and negative predictive value of 0.18 (0.15, 0.21) and 0.97 (0.96, 0.98). Conclusion: EDLIPS may help identify patients at risk for ALI development early in the course of their ED presentation. This novel model may detect at-risk patients for treatment optimization and identify potential patients for ALI prevention trials
Starburst99: Synthesis Models for Galaxies with Active Star Formation
Starburst99 is a comprehensive set of model predictions for
spectrophotometric and related properties of galaxies with active star
formation. The models are an improved and extended version of the data set
previously published by Leitherer & Heckman (1995). We have upgraded our code
by implementing the latest set of stellar evolution models of the Geneva group
and the model atmosphere grid compiled by Lejeune et al. (1997). Several
predictions which were not included in the previous publication are shown here
for the first time. The models are presented in a homogeneous way for five
metallicities between Z = 0.040 and 0.001 and three choices of the initial mass
function. The age coverage is 10^6 to 10^9 yr. We also show the spectral energy
distributions which are used to compute colors and other quantities. The full
data set is available for retrieval at
http://www.stsci.edu/science/starburst99/. This website allows users to run
specific models with non-standard parameters as well. We also make the source
code available to the community.Comment: 32 pages, LaTeX. All the Figures and the summary Table are located at
http://www.stsci.edu/science/starburst99/, ApJ accepte
Synthetic High-Resolution Line Spectra of Star-Forming Galaxies Below 1200A
We have generated a set of far-ultraviolet stellar libraries using spectra of
OB and Wolf-Rayet stars in the Galaxy and the Large and Small Magellanic Cloud.
The spectra were collected with the Far Ultraviolet Spectroscopic Explorer and
cover a wavelength range from 1003.1 to 1182.7A at a resolution of 0.127A. The
libraries extend from the earliest O- to late-O and early-B stars for the
Magellanic Cloud and Galactic libraries, respectively. Attention is paid to the
complex blending of stellar and interstellar lines, which can be significant,
especially in models using Galactic stars. The most severe contamination is due
to molecular hydrogen. Using a simple model for the H line strength, we
were able to remove the molecular hydrogen lines in a subset of Magellanic
Cloud stars. Variations of the photospheric and wind features of CIII 1176, OVI
1032, 1038, PV 1118, 1128, and SIV 1063, 1073, 1074 are discussed as a function
of temperature and luminosity class. The spectral libraries were implemented
into the LavalSB and Starburst99 packages and used to compute a standard set of
synthetic spectra of star-forming galaxies. Representative spectra are
presented for various initial mass functions and star formation histories. The
valid parameter space is confined to the youngest ages of less than 10 Myr for
an instantaneous burst, prior to the age when incompleteness of spectral types
in the libraries sets in. For a continuous burst at solar metallicity, the
parameter space is not limited. The suite of models is useful for interpreting
the restframe far-ultraviolet in local and high-redshift galaxies.Comment: 33 pages including 13 figures, accepted for publication in Ap
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Towards Prevention of Acute Lung Injury: Frequency and Outcomes of Emergency Department Patients At-Risk: A Multicenter Cohort Study
Background: Few emergency department (ED) evaluations on acute lung injury (ALI) have been carried out; hence, we sought to describe a cohort of hospitalized ED patients at risk for ALI development. Methods: Patients presenting to the ED with at least one predisposing condition to ALI were included in this study, a subgroup analysis of a multicenter observational cohort study (USCIITG-LIPS 1). Patients who met ALI criteria within 6 h of initial ED assessment, received end-of-life care, or were readmitted during the study period were excluded. Primary outcome was frequency of ALI development; secondary outcomes were ICU and hospital mortality. Results: Twenty-two hospitals enrolled 4,361 patients who were followed from the ED to hospital discharge. ALI developed in 303 (7.0 %) patients at a median onset of 2 days (IQR 2–5). Of the predisposing conditions, frequency of ALI development was highest in patients who had aortic surgery (43 %) and lowest in patients with pancreatitis (2.8 %). Compared to patients who did not develop ALI, those who did had higher ICU (24 % vs. 3.0 %, p < 0.001) and hospital (28 % vs. 4.6 %, p < 0.001) mortality, and longer hospital length of stay (16 vs. 5 days, p < 0.001). Among the 22 study sites, frequency of ALI development varied from less than 1 % to more than 12 % after adjustment for APACHE II. Conclusions: Seven percent of hospitalized ED patients with at least one predisposing condition developed ALI. The frequency of ALI development varied significantly according to predisposing conditions and across institutions. Further research is warranted to determine the factors contributing to ALI development
Trauma Simulation Training Increases Confidence Levels in Prehospital Personnel Performing Life-Saving Interventions in Trauma Patients
Introduction. Limited evidence is available on simulation training of prehospital care providers, specifically the use of tourniquets and needle decompression. This study focused on whether the confidence level of prehospital personnel performing these skills improved through simulation training. Methods. Prehospital personnel from Alachua County Fire Rescue were enrolled in the study over a 2-to 3-week period based on their availability. Two scenarios were presented to them: a motorcycle crash resulting in a leg amputation requiring a tourniquet and an intoxicated patient with a stab wound, who experienced tension pneumothorax requiring needle decompression. Crews were asked to rate their confidence levels before and after exposure to the scenarios. Timing of the simulation interventions was compared with actual scene times to determine applicability of simulation in measuring the efficiency of prehospital personnel. Results. Results were collected from 129 participants. Pre-and postexposure scores increased by a mean of 1.15 (SD 1.32; 95% CI, 0.88-1.42; < 0.001). Comparison of actual scene times with simulated scene times yielded a 1.39-fold difference (95% CI, 1.25-1.55) for Scenario 1 and 1.59 times longer for Scenario 2 (95% CI, 1.43-1.77). Conclusion. Simulation training improved prehospital care providers' confidence level in performing two life-saving procedures
Physical parameters of erupting Luminous Blue Variables: NGC 2363-V1 caught in the act
A quantitative study of the Luminous Blue Variable NGC 2363-V1 in the
Magellanic galaxy NGC 2366 (D = 3.44 Mpc) is presented, based on ultraviolet
and optical HST/STIS spectroscopy. Contemporary WFPC2 and WHT imaging reveals a
modest V-band brightness increase of ~ 0.2 mag per year between 1996 January
and 1997 November, reaching V=17.4 mag, corresponding to Mv=-10.4 mag.
Subsequently, V1 underwent a similar decrease in V-band brightness, together
with a UV brightening of 0.35 mag from 1997 November to 1999 November.
The optical spectrum of V1 is dominated by H emission lines, with Fe II, He I
and Na I also detected. In the ultraviolet, a forest of Fe absorption features
and numerous absorption lines typical of mid-B supergiants are observed. From a
spectral analysis with the non-LTE, line-blanketed code of Hillier & Miller
(1998), we derive stellar parameters of T*=11kK, R*=420Ro, log(L/Lo)=6.35
during 1997 November, and T*=13kK, R*=315Ro, log(L/Lo)=6.4 for 1999 July. The
wind properties of V1 are also exceptional, with Mdot ~ 4.4 x 10e-4 Mo/yr and
300 km/s, allowing for a clumped wind (filling factor = 0.3),
and assuming H/He ~ 4 by number.
The presence of Fe lines in the UV and optical spectrum of V1 permits an
estimate of the heavy elemental abundance of NGC 2363 from our spectral
synthesis. Although some deficiencies remain, allowance for charge exchange
reactions in our calculations supports a SMC-like metallicity, that has
previously been determined for NGC 2363 from nebular oxygen diagnostics.
Considering a variety of possible progenitor stars, V1 has definitely
undergone a giant eruption, with a substantial increase in stellar luminosity,
radius, and almost certainly mass-loss rate.Comment: 29 pages, 10 figures, Submitted to Ap
Portrait of Candida albicans Adherence Regulators
Cell-substrate adherence is a fundamental property of microorganisms that enables them to exist in biofilms. Our study focuses on adherence of the fungal pathogen Candida albicans to one substrate, silicone, that is relevant to device-associated infection. We conducted a mutant screen with a quantitative flow-cell assay to identify thirty transcription factors that are required for adherence. We then combined nanoString gene expression profiling with functional analysis to elucidate relationships among these transcription factors, with two major goals: to extend our understanding of transcription factors previously known to govern adherence or biofilm formation, and to gain insight into the many transcription factors we identified that were relatively uncharacterized, particularly in the context of adherence or cell surface biogenesis. With regard to the first goal, we have discovered a role for biofilm regulator Bcr1 in adherence, and found that biofilm regulator Ace2 is a major functional target of chromatin remodeling factor Snf5. In addition, Bcr1 and Ace2 share several target genes, pointing to a new connection between them. With regard to the second goal, our findings reveal existence of a large regulatory network that connects eleven adherence regulators, the zinc-response regulator Zap1, and approximately one quarter of the predicted cell surface protein genes in this organism. This limited yet sensitive glimpse of mutant gene expression changes had thus defined one of the broadest cell surface regulatory networks in C. albicans
People and their partners living with Parkinson's and other neurodegenerative diseases: systems' diseases that call for systems' approaches.
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