On the deuterium abundance and the importance of stellar mass loss in the interstellar and intergalactic medium

We quantify the gas-phase abundance of deuterium and fractional contribution of stellar mass loss to the gas in cosmological zoom-in simulations from the Feedback In Realistic Environments project. At low metallicity, our simulations confirm that the deuterium abundance is very close to the primordial value. The chemical evolution of the deuterium abundance that we derive here agrees quantitatively with analytical chemical evolution models. We furthermore find that the relation between the deuterium and oxygen abundance exhibits very little scatter. We compare our simulations to existing high-redshift observations in order to determine a primordial deuterium fraction of 2.549 +/- 0.033 x 10^-5 and stress that future observations at higher metallicity can also be used to constrain this value. At fixed metallicity, the deuterium fraction decreases slightly with decreasing redshift, due to the increased importance of mass loss from intermediate-mass stars. We find that the evolution of the average deuterium fraction in a galaxy correlates with its star formation history. Our simulations are consistent with observations of the Milky Way's interstellar medium: the deuterium fraction at the solar circle is 85-92 per cent of the primordial deuterium fraction. We use our simulations to make predictions for future observations. In particular, the deuterium abundance is lower at smaller galactocentric radii and in higher mass galaxies, showing that stellar mass loss is more important for fuelling star formation in these regimes (and can even dominate). Gas accreting onto galaxies has a deuterium fraction above that of the galaxies' interstellar medium, but below the primordial fraction, because it is a mix of gas accreting from the intergalactic medium and gas previously ejected or stripped from galaxies.Comment: Accepted for publication in MNRAS. Revised version: expanded discussion and added Figure 2 (residual dependence on iron abundance

Respiratory symptoms in preterm infants: burden of disease in the first year of life

OBJECTIVE: While respiratory symptoms in the first year of life are relatively well described for term infants, data for preterm infants are scarce. We aimed to describe the burden of respiratory disease in a group of preterm infants with and without bronchopulmonary dysplasia (BPD) and to assess the association of respiratory symptoms with perinatal, genetic and environmental risk factors. METHODS: Single centre birth cohort study: prospective recording of perinatal risk factors and retrospective assessment of respiratory symptoms during the first year of life by standardised questionnaires. MAIN OUTCOME MEASURES: Cough and wheeze (common symptoms), re-hospitalisation and need for inhalation therapy (severe outcomes). PATIENTS: 126 preterms (median gestational age 28.7 weeks; 78 with, 48 without BPD) hospitalised at the University Children's Hospital of Bern, Switzerland 1999-2006. RESULTS: Cough occurred in 80%, wheeze in 44%, re-hospitalisation in 25% and long term inhalation therapy in wheezers in 13% of the preterm infants. Using logistic regression, the main risk factor for common symptoms was frequent contact with other children. Severe outcomes were associated with maximal peak inspiratory pressure, arterial cord blood pH, APGAR- and CRIB-Score. CONCLUSIONS: Cough in preterm infants is as common as in term infants, whereas wheeze, inhalation therapy and re-hospitalisations occur more often. Severe outcomes are associated with perinatal risk factors. Preterm infants who did not qualify for BPD according to latest guidelines also showed a significant burden of respiratory disease in the first year of life

The impact of stellar feedback on hot gas in galaxy haloes: the Sunyaev–Zel'dovich effect and soft X-ray emission

The thermal Sunyaev–Zel'dovich (SZ) effect and soft X-ray emission are routinely observed around massive galaxies and in galaxy groups and clusters. We study these observational diagnostics of galaxy haloes for a suite of cosmological ‘zoom-in’ simulations from the ‘Feedback In Realistic Environments’ project, which spans a large range in halo mass (10^(10–13) M_⊙). We explore the effect of stellar feedback on the hot gas observables. The properties of our simulated groups, such as baryon fractions, SZ flux, and X-ray luminosities (LX), are broadly consistent with existing observations, even though feedback from active galactic nuclei is not included. We make predictions for future observations of lower mass objects for both SZ and diffuse X-ray measurements, finding that they are not just scaled-down versions of massive galaxies, but more strongly affected by galactic winds driven by star formation. Low-mass haloes (≲ 10^(11) M_⊙) retain a low fraction of their baryons, which results in a strong suppression of the SZ signal. Our simulations therefore predict a scaling with halo mass that is steeper than self-similar for haloes less massive than 10^(13) M_⊙. For halo masses ≲ 10^(12) M_⊙, LX is time variable and correlated primarily with the star formation rate (SFR). For these objects, the diffuse X-ray emission is powered mostly by galactic winds and the gas dominating the X-ray emission is flowing out with radial velocities close to the halo's circular velocity. For halo masses ≳ 10^(13) M_⊙, on the other hand, LX is much less variable and not correlated with the SFR, because the emission originates from the quasi-hydrostatic, virialized halo gas

Thymus Extracellular Matrix-Derived Scaffolds Support Graft-Resident Thymopoiesis and Long-Term In Vitro Culture of Adult Thymic Epithelial Cells

The thymus provides the physiological microenvironment critical for the development of T lymphocytes, the cells that orchestrate the adaptive immune system to generate an antigen-specific response. A diverse population of stroma cells provides surface-bound and soluble molecules that orchestrate the intrathymic maturation and selection of developing T cells. Forming an intricate 3D architecture, thymic epithelial cells (TEC) represent the most abundant and important constituent of the thymic stroma. Effective models for in and ex vivo use of adult TEC are still wanting, limiting the engineering of functional thymic organoids and the understanding of the development of a competent immune system. Here a 3D scaffold is developed based on decellularized thymic tissue capable of supporting in vitro and in vivo thymopoiesis by both fetal and adult TEC. For the first time, direct evidences of feasibility for sustained graft-resident T-cell development using adult TEC as input are provided. Moreover, the scaffold supports prolonged in vitro culture of adult TEC, with a retained expression of the master regulator Foxn1. The success of engineering a thymic scaffold that sustains adult TEC function provides unprecedented opportunities to investigate thymus development and physiology and to design and implement novel strategies for thymus replacement therapies

The Origins of the Circumgalactic Medium in the FIRE Simulations

We use a particle tracking analysis to study the origins of the circumgalactic medium (CGM), separating it into (1) accretion from the intergalactic medium (IGM), (2) wind from the central galaxy, and (3) gas ejected from other galaxies. Our sample consists of 21 FIRE-2 simulations, spanning the halo mass range log(Mh/Msun) ~ 10-12 , and we focus on z=0.25 and z=2. Owing to strong stellar feedback, only ~L* halos retain a baryon mass >~50% of their cosmic budget. Metals are more efficiently retained by halos, with a retention fraction >~50%. Across all masses and redshifts analyzed >~60% of the CGM mass originates as IGM accretion (some of which is associated with infalling halos). Overall, the second most important contribution is wind from the central galaxy, though gas ejected or stripped from satellites can contribute a comparable mass in ~L* halos. Gas can persist in the CGM for billions of years, resulting in well-mixed halo gas. Sight lines through the CGM are therefore likely to intersect gas of multiple origins. For low-redshift ~L* halos, cool gas (T<10^4.7 K) is distributed on average preferentially along the galaxy plane, however with strong halo-to-halo variability. The metallicity of IGM accretion is systematically lower than the metallicity of winds (typically by >~1 dex), although CGM and IGM metallicities depend significantly on the treatment of subgrid metal diffusion. Our results highlight the multiple physical mechanisms that contribute to the CGM and will inform observational efforts to develop a cohesive picture.Comment: 23 pages, 22 figures. Minor revisions from previous version. Online interactive visualizations available at zhafen.github.io/CGM-origins and zhafen.github.io/CGM-origins-pathline

A new scoring system in Cystic Fibrosis: statistical tools for database analysis – a preliminary report

<p>Abstract</p> <p>Background</p> <p>Cystic fibrosis is the most common fatal genetic disorder in the Caucasian population. Scoring systems for assessment of Cystic fibrosis disease severity have been used for almost 50 years, without being adapted to the milder phenotype of the disease in the 21^stcentury. The aim of this current project is to develop a new scoring system using a database and employing various statistical tools. This study protocol reports the development of the statistical tools in order to create such a scoring system.</p> <p>Methods</p> <p>The evaluation is based on the Cystic Fibrosis database from the cohort at the Royal Children's Hospital in Melbourne. Initially, unsupervised clustering of the all data records was performed using a range of clustering algorithms. In particular incremental clustering algorithms were used. The clusters obtained were characterised using rules from decision trees and the results examined by clinicians. In order to obtain a clearer definition of classes expert opinion of each individual's clinical severity was sought. After data preparation including expert-opinion of an individual's clinical severity on a 3 point-scale (mild, moderate and severe disease), two multivariate techniques were used throughout the analysis to establish a method that would have a better success in feature selection and model derivation: 'Canonical Analysis of Principal Coordinates' and 'Linear Discriminant Analysis'. A 3-step procedure was performed with (1) selection of features, (2) extracting 5 severity classes out of a 3 severity class as defined per expert-opinion and (3) establishment of calibration datasets.</p> <p>Results</p> <p>(1) Feature selection: CAP has a more effective "modelling" focus than DA.</p> <p>(2) Extraction of 5 severity classes: after variables were identified as important in discriminating contiguous CF severity groups on the 3-point scale as mild/moderate and moderate/severe, Discriminant Function (DF) was used to determine the new groups mild, intermediate moderate, moderate, intermediate severe and severe disease. (3) Generated confusion tables showed a misclassification rate of 19.1% for males and 16.5% for females, with a majority of misallocations into adjacent severity classes particularly for males.</p> <p>Conclusion</p> <p>Our preliminary data show that using CAP for detection of selection features and Linear DA to derive the actual model in a CF database might be helpful in developing a scoring system. However, there are several limitations, particularly more data entry points are needed to finalize a score and the statistical tools have further to be refined and validated, with re-running the statistical methods in the larger dataset.</p

Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab

We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass distribution is obtained that is consistent with W decay and inconsistent with the background prediction by 3.3 standard deviations. From this peak we measure the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet channel.Comment: 20 pages, 4 figures, submitted to PR