X-Ray Spectroscopy of Stars

(abridged) Non-degenerate stars of essentially all spectral classes are soft X-ray sources. Low-mass stars on the cooler part of the main sequence and their pre-main sequence predecessors define the dominant stellar population in the galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense, of X-ray spectra from the solar corona. X-ray emission from cool stars is indeed ascribed to magnetically trapped hot gas analogous to the solar coronal plasma. Coronal structure, its thermal stratification and geometric extent can be interpreted based on various spectral diagnostics. New features have been identified in pre-main sequence stars; some of these may be related to accretion shocks on the stellar surface, fluorescence on circumstellar disks due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot stars clearly dominate the interaction with the galactic interstellar medium: they are the main sources of ionizing radiation, mechanical energy and chemical enrichment in galaxies. High-energy emission permits to probe some of the most important processes at work in these stars, and put constraints on their most peculiar feature: the stellar wind. Here, we review recent advances in our understanding of cool and hot stars through the study of X-ray spectra, in particular high-resolution spectra now available from XMM-Newton and Chandra. We address issues related to coronal structure, flares, the composition of coronal plasma, X-ray production in accretion streams and outflows, X-rays from single OB-type stars, massive binaries, magnetic hot objects and evolved WR stars.Comment: accepted for Astron. Astrophys. Rev., 98 journal pages, 30 figures (partly multiple); some corrections made after proof stag

Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median $z\sim 0.03$). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between $z\sim 0.6$ and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July

Distance to health services influences insecticide-treated net possession and use among six to 59 month-old children in Malawi

<p>Abstract</p> <p>Background</p> <p>Health ministries and providers are rapidly scaling up insecticide-treated nets (ITN) distribution to control malaria, yet possession and proper use typically remain below targeted levels. In Malawi, health facilities (HFs) are currently the principal points of ITN distribution, making it important to understand how access to these ITN sources affects ownership, possession, and use. The authors evaluated the association between proximity to HFs and ITN possession or use among Malawian children six to 59 months of age.</p> <p>Methods</p> <p>A household malaria survey undertaken in eight districts of Malawi during 2007 was used to characterize ITN possession and use. The location of each respondent's household was geocoded as was those of Ministry of Health (MoH) HFs and other health centres. Euclidean distance from each household to the nearest HF was calculated. Patterns of net possession and use were determined through descriptive methods. The authors then analysed the significance of distance and ITN possession/use through standard statistical tests, including logistic regression.</p> <p>Results</p> <p>Median distance to HFs was greater among households that did not possess ITNs and did not use an ITN the previous evening. Descriptive statistical methods confirmed a pattern of decreasing ITN possession and use with increasing distance from HFs. Logistic regression showed the same statistically significant association of distance to HFs, even when controlling for age and gender of the child, ratio of nets to children in household, community net possession and use, and household material wealth.</p> <p>Conclusions</p> <p>Strategies that exclusively distribute ITNs through HFs are likely to be less effective in increasing possession and use in communities that are more distant from those health services. Health providers should look towards community-based distribution services that take ITNs directly to community members to more effectively scale up ITN possession and regular use aimed at protecting children from malaria.</p

Contributors to organ damage in childhood lupus: Corticosteroid use and disease activity

\ua9 2024 The Author(s) 2024 Published by Oxford University Press on behalf of the British Society for Rheumatology.Objectives: Awareness of paediatric-specific predictors of damage in childhood lupus is needed to inform mitigation measures. The objective of this study was to ascertain how clinical and demographic variables correlate with damage accrual and identify predictors of damage. Methods: This analysis included UK JSLE Cohort Study participants. Univariable and multivariable Prentice-Williams-Peterson models investigated how demographic and clinical factors influenced the hazards of new damage. Analyses were performed across the entire cohort, in patients with minimal disease activity marked by a time-adjusted average SLEDAI-2K score (AMS) of ≤2, in patients with low activity (AMS of ≤4), patients with moderate-to-high activity (AMS of &gt;4) and patients with no CS use. Results: Within the entire cohort (n = 430), factors associated with damage included: any methylprednisolone [hazard ratio, HR 2.20 (CI 1.33-3.62)], time-adjusted mean Physician\u27s Global Assessment (PGA) [HR 2.87 (CI 1.48-5.56)] and AMS score [HR 1.13 (CI 1.03-1.24), all P &lt; 0.05]. Within the low activity subgroup, any methylprednisolone [HR 2.61 (CI 1.04-6.53)] and time-adjusted mean PGA [HR 3.41 (CI 1.52-7.76)] were associated with damage (both P &lt; 0.05). Within the moderate-to-high activity subgroup, any methylprednisolone [HR 2.29 (CI 1.31-4.00)], time-adjusted mean PGA [HR 2.66, (CI 1.20-5.87)] and AMS score [HR 1.15 (CI 1.03-1.29)] were predictive of damage (all P &lt; 0.05). Baseline organ damage was predictive of subsequent damage accrual in the minimal disease activity subgroup [HR 1.33 (CI 1.78-8.08)] and the no CSs subgroup [HR 3.64 (CI 1.83-7.24), both P &lt; 0.005]. Conclusion: Disease activity levels (AMS/PGA) and proxy indicators (methylprednisolone exposure, baseline damage) were found to be key predictors of damage accrual. This highlights the importance of practical strategies, such as treat-to-target, for reducing disease activity and long-term treatment toxicity

Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median $z\sim 0.03$). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between $z\sim 0.6$ and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July

Clinical and laboratory phenotypes in juvenile-onset Systemic Lupus Erythematosus across ethnicities in the UK.

Systemic lupus erythematosus (SLE) is a systemic autoimmune/inflammatory disease. Patients diagnosed with juvenile-onset SLE (jSLE), when compared to individuals with adult-onset SLE, develop more severe organ involvement, increased disease activity and greater tissue and organ damage. In adult-onset SLE, clinical characteristics, pathomechanisms, disease progression and outcomes do not only vary between individuals and age groups, but also ethnicities. However, in children and young people, the influence of ethnicity on disease onset, phenotype and outcome has not been investigated in detail. In this study, we investigated clinical and laboratory characteristics in pediatric SLE patients from different ethnic backgrounds (White Caucasian, Asian, Black African/Caribbean) accessing data from a national cohort of jSLE patients (the UK JSLE Cohort Study). Among jSLE patients in the UK, ethnicity affects both the disease's clinical course and outcomes. At diagnosis, Black African/Caribbean jSLE patients show more "classical" laboratory and clinical features when compared to White Caucasian or Asian patients. Black African/Caribbean jSLE patients exhibit more renal involvement and more frequently receive cyclophosphamide and rituximab. Studies targeting ethnicity-specific contributors to disease expression and phenotypes are necessary to improve our pathophysiological understanding, diagnosis and treatment of jSLE

Clinical and laboratory characteristics in juvenile-onset systemic lupus erythematosus across age groups

BACKGROUND Systemic lupus erythematous (SLE) is a systemic autoimmune/inflammatory condition. Approximately 15–20% of patients develop symptoms before their 18th birthday and are diagnosed with juvenile-onset SLE (JSLE). Gender distribution, clinical presentation, disease courses and outcomes vary significantly between JSLE patients and individuals with adult-onset SLE. This study aimed to identify age-specific clinical and/or serological patterns in JSLE patients enrolled to the UK JSLE Cohort Study. METHODS Patient records were accessed and grouped based on age at disease-onset: pre-pubertal (≤7 years), peri-pubertal (8–13 years) and adolescent (14–18 years). The presence of American College of Rheumatology (ACR) classification criteria, laboratory results, disease activity [British Isles Lupus Assessment Group (BILAG) and Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2 K) scores] and damage [Systemic Lupus International Collaborating Clinics (SLICC) damage index] were evaluated at diagnosis and last follow up. RESULTS A total of 418 JSLE patients were included in this study: 43 (10.3%) with pre-pubertal disease onset; 240 (57.4%) with peri-pubertal onset and 135 (32.3%) were diagnosed during adolescence. At diagnosis, adolescent JSLE patients presented with a higher number of ACR criteria when compared with pre-pubertal and peri-pubertal patients [pBILAG2004 scores: 9(4–20] vs. 7(3–13] vs. 7(3–14], respectively, p = 0.015] with increased activity in the following BILAG domains: mucocutaneous (p = 0.025), musculoskeletal (p = 0.029), renal (p = 0.027) and cardiorespiratory (p = 0.001). Furthermore, adolescent JSLE patients were more frequently ANA-positive (p = 0.034) and exhibited higher anti-dsDNA titres (p = 0.001). Pre-pubertal individuals less frequently presented with leukopenia (p = 0.002), thrombocytopenia (p = 0.004) or low complement (p = 0.002) when compared with other age groups. No differences were identified in disease activity (pBILAG2004 score), damage (SLICC damage index) and the number of ACR criteria fulfilled at last follow up. CONCLUSIONS Disease presentations and laboratory findings vary significantly between age groups within a national cohort of JSLE patients. Patients diagnosed during adolescence exhibit greater disease activity and “classic” autoantibody, immune cell and complement patterns when compared with younger patients. This supports the hypothesis that pathomechanisms may vary between patient age groups

Validation of childhood lupus specific targets: Ensuring accurate assessment of disease control in younger, lighter paediatric patients

\ua9 2025 The Author(s).Objectives: To validate novel childhood-onset systemic lupus erythematosus (cSLE) treat-To-Target targets including childhood lupus low disease activity state (cLLDAS), cSLE clinical remission on steroids (cCR) and cSLE clinical remission off steroids (cCR-0), as compared with adult-onset SLE (aSLE) targets. Methods: Attainment of the aforementioned cSLE-specific and aSLE-specific targets (LLDAS, DORIS 2021 Remission) was assessed at each visit in UK JSLE Cohort Study patients. Univariable and multivariable Prentice-Williams-Peterson (PWP) gap-Time models investigated the impact of target attainment on new damage and severe flare. Results: The cohort included 430 cSLE patients. Attainability was comparable between corresponding cSLE and aSLE targets. Achieving cLLDAS (hazard ratio [HR] 0.18 [95% CI: 0.14, 0.23]), cCR (HR 0.18 [0.13, 0.23]) and cCR-0 (HR 0.17 [0.13, 0.23]) reduced the risk of severe flare (all P &lt; 0.001). Risk of new damage was reduced in those reaching cLLDAS (HR 0.22 [0.11, 0.44]), cCR (HR 0.25 [0.13, 0.49]) and cCR-0 (HR 0.30 [0.15, 0.60]) (all P &lt; 0.001). Inappropriate attainment of LLDAS and DORIS remission occurred at 35 and 52 visits, respectively, in younger (median age 7.3 and 8.8 years, respectively) and lighter (median weight 26.8 and 37.1 kg, respectively) patients whilst on prednisolone doses that precluded cSLE target attainment (median 0.17 [IQR 0.16-0.24] and 0.13 [IQR 0.11-0.16] mg/kg/day, respectively). Conclusions: This study validates novel paediatric-specific targets, demonstrating that achieving cLLDAS, cCR and cCR-0 reduces risks of new damage and severe flare, which is comparable to aSLE targets. Using cSLE-specific targets prevents misclassification of disease activity in paediatric patients, enabling more accurate disease control assessments in younger, lighter patients