Tracing our Milky Way's nucleosynthetic past and present using stars and nebulae

Constraining Galactic chemical evolution (GCE) is critical for understanding the star formation and merger history of the Milky Way and has implications for several fields of astrophysics including exoplanet science and galaxy evolution more broadly. Stars are excellent tracers GCE because they serve as chemical "time capsules" with surface compositions that generally reflect the composition of their natal birth environment. Planetary nebulae are also excellent tracers of GCE because they chemically contain the complete nucleosynthetic output of their asymptotic giant branch (AGB) star progenitors which are important contributors to the Galactic reservoir of neutron-capture elements. This dissertation presents four projects that leverage the power of stars and planetary nebulae to place critical empirical constraints on GCE with particular focus on the neutron-capture elements and the Milky Way disk. Project 1 supports ongoing efforts to constrain AGB star nucleosynthesis by chemically characterizing eight Milky Way planetary nebulae with the Low Resolution Spectrograph 2 (LRS2) on the Hobby-Eberly telescope at McDonald Observatory. Project 2 explores the chemical similarity of stars born together, which directly impacts the chemical distribution of disk stars, by characterizing 18 newfound stellar associations using data from the third data release of the GALactic Archaeology with HERMES (GALAH) spectroscopic survey. Project 3 explores the chemical similarity of disk stars that are not born together, a measure of the chemical diversity of the disk, by measuring the so-called "chemical doppelganger rate" in the GALAH survey, the rate at which random, kinematically unassociated pairs of field stars appear as chemically similar as stars born together. Finally, Project 4 uses the Tull Coude Spectrograph on the 2.7m telescope at McDonald Observatory to unveil hidden chemical doppelgangers among APOGEE-identified chemically similar stars. Together, these works provide key empirical constraints on GCE and highlight the unique behavior of neutron-capture elements across Milky Way disk stars.Astronom

Chemical Doppelgangers in GALAH DR3: the Distinguishing Power of Neutron-Capture Elements Among Milky Way Disk Stars

The observed chemical diversity of Milky Way stars places important constraints on Galactic chemical evolution and the mixing processes that operate within the interstellar medium. Recent works have found that the chemical diversity of disk stars is low. For example, the APOGEE "chemical doppelganger rate," or the rate at which random pairs of field stars appear as chemically similar as stars born together, is high, and the chemical distributions of APOGEE stars in some Galactic populations are well-described by two-dimensional models. However, limited attention has been paid to the heavy elements (Z > 30) in this context. In this work, we probe the potential for neutron-capture elements to enhance the chemical diversity of stars by determining their effect on the chemical doppelganger rate. We measure the doppelganger rate in GALAH DR3, with abundances rederived using The Cannon, and find that considering the neutron-capture elements decreases the doppelganger rate from 2.2% to 0.4%, nearly a factor of 6, for stars with -0.1 < [Fe/H] < 0.1. While chemical similarity correlates with similarity in age and dynamics, including neutron-capture elements does not appear to select stars that are more similar in these characteristics. Our results highlight that the neutron-capture elements contain information that is distinct from that of the lighter elements and thus add at least one dimension to Milky Way abundance space. This work illustrates the importance of considering the neutron-capture elements when chemically characterizing stars and motivates ongoing work to improve their atomic data and measurements in spectroscopic surveys.Comment: 23 pages, 16 figures, 1 table. Submitted to AAS Journals, comments welcome. Associated catalog of high precision, Cannon-rederived abundances for GALAH giants to be made publicly available upon acceptance and available now upon request. See Walsen et al. 2023 for a complementary, high precision, Cannon-rederived abundance catalog for GALAH solar twin

ELemental abundances of Planets and brown dwarfs Imaged around Stars (ELPIS): I. Potential Metal Enrichment of the Exoplanet AF Lep b and a Novel Retrieval Approach for Cloudy Self-luminous Atmospheres

AF Lep A+b is a remarkable planetary system hosting a gas-giant planet that has the lowest dynamical mass among directly imaged exoplanets. We present an in-depth analysis of the atmospheric composition of the star and planet to probe the planet's formation pathway. Based on new high-resolution spectroscopy of AF Lep A, we measure a uniform set of stellar parameters and elemental abundances (e.g., [Fe/H] = $-0.27 \pm 0.31$ dex). The planet's dynamical mass ($2.8^{+0.6}_{-0.5}$ M$_{\rm Jup}$) and orbit are also refined using published radial velocities, relative astrometry, and absolute astrometry. We use petitRADTRANS to perform chemically-consistent atmospheric retrievals for AF Lep b. The radiative-convective equilibrium temperature profiles are incorporated as parameterized priors on the planet's thermal structure, leading to a robust characterization for cloudy self-luminous atmospheres. This novel approach is enabled by constraining the temperature-pressure profiles via the temperature gradient $(d\ln{T}/d\ln{P})$, a departure from previous studies that solely modeled the temperature. Through multiple retrievals performed on different portions of the $0.9-4.2$ $\mu$m spectrophotometry, along with different priors on the planet's mass and radius, we infer that AF Lep b likely possesses a metal-enriched atmosphere ([Fe/H] $> 1.0$ dex). AF Lep b's potential metal enrichment may be due to planetesimal accretion, giant impacts, and/or core erosion. The first process coincides with the debris disk in the system, which could be dynamically excited by AF Lep b and lead to planetesimal bombardment. Our analysis also determines $T_{\rm eff} \approx 800$ K, $\log{(g)} \approx 3.7$ dex, and the presence of silicate clouds and dis-equilibrium chemistry in the atmosphere. Straddling the L/T transition, AF Lep b is thus far the coldest exoplanet with suggested evidence of silicate clouds.Comment: AJ, in press. Main text: Pages 1-32, Figures 1-15, Tables 1-6. All figures and tables after References belong to the Appendix (Pages 32-58, Figures 16-20, Table 7). For supplementary materials, please refer to the Zenodo repository https://doi.org/10.5281/zenodo.826746

Screening for psychological and mental health difficulties in young people who offend: a systematic review and decision model

Background: There is policy interest in the screening and treatment of mental health problems in young people who offend, but the value of such screening is not yet known. Objectives: To assess the diagnostic test accuracy of screening measures for mental health problems in young people who offend; to evaluate the clinical effectiveness and cost-effectiveness of screening and treatment; to model estimates of cost; to assess the evidence base for screening against UK National Screening Committee criteria; and to identify future research priorities. Data sources: In total, 25 electronic databases including MEDLINE, PsycINFO, EMBASE and The Cochrane Library were searched from inception until April 2011. Reverse citation searches of included studies were undertaken and reference list of included studies were examined. Review methods: Two reviewers independently examined titles and abstracts and extracted data from included studies using a standardised form. The inclusion criteria for the review were (1) population – young offenders (aged 10–21 years); (2) intervention/instrument – screening instruments for mental health problems, implementation of a screening programme or a psychological or pharmacological intervention as part of a clinical trial; (3) comparator – for diagnostic test accuracy studies, any standardised diagnostic interview; for trials, any comparator; (4) outcomes – details of diagnostic test accuracy, mental health outcomes over the short or longer term or measurement of cost data; and (5) study design – for diagnostic test accuracy studies, any design; for screening programmes, randomised controlled trials or controlled trials; for clinical effectiveness studies, randomised controlled trials; for economic studies, economic evaluations of screening strategies or interventions. Results: Of 13,580 studies identified, nine, including eight independent samples, met the inclusion criteria for the diagnostic test accuracy and validity of screening measures review. Screening accuracy was typically modest. No studies examined the clinical effectiveness of screening, although 10 studies were identified that examined the clinical effectiveness of interventions for mental health problems. There were too few studies to make firm conclusions about the clinical effectiveness of treatments in this population. No studies met the inclusion criteria for the assessment of the cost-effectiveness of screening or treatment. An exemplar decision model was developed for depression, which identified a number of the likely key drivers of uncertainty, including the prevalence of unidentified mental health problems, the severity of mental health problems and their relationship to generic measures of outcome and the impact of treatment on recidivism. The information evaluated as part of the review was relevant to five of the UK National Screening Committee criteria. On the basis of the above results, none of the five criteria was met. Limitations: The conclusions of the review are based on limited evidence. Conclusions are tentative and the decision model should be treated as an exemplar. Conclusions: Evidence on the clinical effectiveness and cost-effectiveness of screening for mental health problems in young people who offend is currently lacking. Future research should consider feasibility trials of clinical interventions to establish important parameters ahead of conducting definitive trials. Future diagnostic studies should compare the diagnostic test accuracy of a range of screening instruments, including those recommended for use in the UK in this population. These studies should be designed to reduce the decision uncertainty identified by the exemplar decision model. Registration: This study is registered as PROSPERO CRD42011001466. Funding: The National Institute for Health Research Health Technology Assessment programme

The Th17/Treg Ratio, IL-1RA and sCD14 Levels in Primary HIV Infection Predict the T-cell Activation Set Point in the Absence of Systemic Microbial Translocation

International audienceImpairment of the intestinal barrier and subsequent microbial translocation (MT) may be involved in chronic immune activation, which plays a central role in HIV pathogenesis. Th17 cells are critical to prevent MT. The aim of the study was to investigate, in patients with primary HIV infection (PHI), the early relationship between the Th17/Treg ratio, monocyte activation and MT and their impact on the T-cell activation set point, which is known to predict disease progression. 27 patients with early PHI were included in a prospective longitudinal study and followed-up for 6 months. At baseline, the Th17/Treg ratio strongly negatively correlated with the proportion of activated CD8 T cells expressing CD38/HLA-DR or Ki-67. Also, the Th17/Treg ratio was negatively related to viral load and plasma levels of sCD14 and IL-1RA, two markers of monocyte activation. In untreated patients, the Th17/Treg ratio at baseline negatively correlated with CD8 T-cell activation at month 6 defining the T-cell activation set point (% HLA-DR + CD38 + and %Ki-67 +). Soluble CD14 and IL-1RA plasma levels also predicted the T-cell activation set point. Levels of I-FABP, a marker of mucosal damages, were similar to healthy controls at baseline but increased at month 6. No decrease in anti-endotoxin core antibody (EndoCAb) and no peptidoglycan were detected during PHI. In addition, 16S rDNA was only detected at low levels in 2 out 27 patients at baseline and in one additional patient at M6. Altogether, data support the hypothesis that T-cell and monocyte activation in PHI are not primarily driven by systemic MT but rather by viral replication. Moreover, the ''innate immune set point'' defined by the early levels of sCD14 and IL-1RA might be powerful early surrogate markers for disease progression and should be considered for use in clinical practice

Georges Perec artisan de la langue

Dans la remarquable fortune posthume que connaît l'œuvre de Georges Perec, aujourd'hui salué comme un « classique », il est frappant que l'approche linguistique de ses textes ait presque toujours été négligée par la critique malgré son orientation d'abord formaliste. De fait, une telle perspective semble interdite par le discours explicite de l'écrivain. Georges Perec, « homme de lettres » au sens où il a affaire « aux lettres de l'alphabet », notait en 1965 : « je n'ai jamais fait vraiment attention aux formes : je ne me suis jamais demandé pourquoi j'écrivais comme ça et pas autrement. » Ce volume prend le contrepied d'un tel discours en se donnant pour objet, au contraire, la langue de l'écrivain Perec. Il réunit donc des approches proprement linguistiques (lexique, ponctuation, énonciation, conséquences de contraintes « dures » comme le lipogramme...) et des réflexions stylistiques, à partir d'une interrogation fondamentale sur l'écriture « blanche ». Si le propos de ce livre n'est pas absolument sans précédents, il est cependant nouveau par beaucoup d'aspects – notamment par la présence, à la fin de l'article inaugural de Paulette Perec, d'une lettre inédite de Georges Perec, adressée en août 1959 à l'un de ses amis.pour Bernard Magn

Patients' characteristics.

<p>Data are expressed as median (IQR).</p>*<p>For one patient experiencing an intercurrent episode associated with high level of inflammation at M6, clinical data from M3 were used.</p>**<p>Twelve patients received ART between baseline and M6. Two patients were lost to follow-up.</p

Longitudinal follow-up of CD8 T-cell activation, CD4 cell counts and of plasma HIV-RNA levels in patients with primary HIV infection.

<p>At baseline (Panel A), frequencies of CD38⁺HLA-DR⁺ CD8 T cells were compared in patients that remained untreated during the 6-month follow-up (n = 13, Untreated) and in patients that have been subsequently treated before M6 (n = 12, Subsequently treated). CD8 T-cell activation was longitudinally assessed in untreated patients (n = 13) by measuring the frequency of CD38⁺HLA-DR⁺ cells (Panel B) and of Ki-67⁺ cells (Panel C) among CD8⁺ T cells at baseline, day 15 (D15), month 1 (M1), month 3 (M3) and month 6 (M6). Panel D illustrates the proportion of CD38⁺HLA-DR⁺ cells among CD8 T cells in untreated patients, in ART-treated patients at M6 and in healthy controls (n = 14). CD4 T cell counts (Panel E) and plasma HIV-1 RNA levels (Panel F) were plotted as a function of time during the 6 months of follow-up in treated (blue lines) and untreated (red lines) patients. Data are expressed as mean ± SEM. Wilcoxon rank tests were performed and p values are indicated between indicated time points for untreated patients (Panels B, C, E, F). Mann-Whitney tests were performed to compare groups of patients (Panels A and D).</p

The Th17/Treg ratio and monocyte activation markers at baseline predict the T-cell activation set point.

<p>Panels depict the relationships between the Th17/Treg ratio (Panel A), plasma levels of sCD14 (Panel B) or IL-1RA (C) at baseline and CD8 T cell activation at month 6. The T-cell activation set point was defined as the frequency of CD8 T cells co-expressing CD38 and HLA-DR or expressing Ki-67 at month 6. Spearman's rank correlation coefficients ‘R’ and corresponding p values are indicated on each panel.</p