The design and performance of the Gaia photometric system

The European Gaia astrometry mission is due for launch in 2011. Gaia will rely on the proven principles of the ESA Hipparcos mission to create an all-sky survey of about one billion stars throughout our Galaxy and beyond, by observing all objects down to 20 mag. Through its massive measurement of stellar distances, motions and multicolour photometry, it will provide fundamental data necessary for unravelling the structure, formation and evolution of the Galaxy. This paper presents the design and performance of the broad- and medium-band set of photometric filters adopted as the baseline for Gaia. The 19 selected passbands (extending from the UV to the far-red), the criteria and the methodology on which this choice has been based are discussed in detail. We analyse the photometric capabilities for characterizing the luminosity, temperature, gravity and chemical composition of stars. We also discuss the automatic determination of these physical parameters for the large number of observations involved, for objects located throughout the entire Hertzsprung-Russell diagram. Finally, the capability of the photometric system (PS) to deal with the main Gaia science case is outline

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

A fine balance of synaptophysin levels underlies efficient retrieval of synaptobrevin II to synaptic vesicles

Synaptobrevin II (sybII) is a vesicular soluble NSF attachment protein receptor (SNARE) protein that is essential for neurotransmitter release, and thus its correct trafficking to synaptic vesicles (SVs) is critical to render them fusion competent. The SV protein synaptophysin binds to sybII and facilitates its retrieval to SVs during endocytosis. Synaptophysin and sybII are the two most abundant proteins on SVs, being present in a 1:2 ratio. Synaptophysin and sybII are proposed to form a large multimeric complex, and the copy number of the proteins in this complex is also in a 1:2 ratio. We investigated the importance of this ratio between these proteins for the localisation and trafficking of sybII in central neurons. SybII was overexpressed in mouse hippocampal neurons at either 1.6 or 2.15-2.35-fold over endogenous protein levels, in the absence or presence of varying levels of synaptophysin. In the absence of exogenous synaptophysin, exogenous sybII was dispersed along the axon, trapped on the plasma membrane and retrieved slowly during endocytosis. Co-expression of exogenous synaptophysin rescued all of these defects. Importantly, the expression of synaptophysin at nerve terminals in a 1:2 ratio with sybII was sufficient to fully rescue normal sybII trafficking. These results demonstrate that the balance between synaptophysin and sybII levels is critical for the correct targeting of sybII to SVs and suggests that small alterations in synaptophysin levels might affect the localisation of sybII and subsequent presynaptic performance

Overdiagnosis of Newborn Hyperbilirubinemia: A Natural Experiment in Quality Improvement Fundamentals.

UNLABELLED: Two hospitals noted increased newborn hyperbilirubinemia coinciding with an undisclosed total serum bilirubin (TSB) assay change. Clinicians rapidly applied quality improvement methodologies to ascertain increased jaundice evaluations, readmissions, and possible safety issues. METHODS: In January 2020, 2 hospitals (A and B) transitioned to a new method of measuring TSB using a new clinical chemistry analyzer (Siemens Atellica CH), which measured TSB by vanadate oxidase assay instead of the previous diazo assay. Five affiliated hospitals (C-G) continued to utilize the diazo assay. This natural experiment led to a comparison of data across the 7 hospitals. We analyzed: (1) TSB levels, (2) hospital hyperbilirubinemia readmissions, and (3) paired TSB measurements comparing the diazo assay and vanadate oxidase method. RESULTS: Compared to the 2019 baseline, Hospitals A and B had a significant increase in TSBs ≥17.0 mg/dl and TSBs ≥20 mg/dl in 2020; Hospitals C-G did not. Readmissions for phototherapy significantly increased in hospitals A and B in 2020 compared to 2019. Paired blood samples showed bias-elevated TSBs by vanadate assay compared to the diazo method. By 2021, the laboratory resumed processing TSB samples by diazo assay, and the frequency of elevated TSBs and hyperbilirubinemia readmissions returned to 2019 levels. CONCLUSIONS: Factitious TSB elevation related to an assay change significantly increased newborn hyperbilirubinemia evaluations and phototherapy readmissions. Imbedded quality improvement methodologies of careful structure, process, and outcomes review hastened resolution

The chronic lymphocytic leukemia comorbidity index (CLL-CI): a three-factor comorbidity model.

PURPOSE: Comorbid medical conditions define a subset of chronic lymphocytic leukemia (CLL) patients with poor outcomes. However, which comorbidities are most predictive remains understudied. EXPERIMENTAL DESIGN: We conducted a retrospective analysis from 10 academic centers to ascertain the relative importance of comorbidities assessed by the Cumulative Illness Rating Scale (CIRS). The influence of specific comorbidities on event-free survival (EFS) was assessed in this derivation dataset using random survival forests to construct a CLL-specific comorbidity index (CLL-CI). Cox models were then fit to this dataset and to a single-center, independent validation dataset. RESULTS: The derivation and validation sets comprised 570 patients (59% receiving Bruton tyrosine kinase inhibitor [BTKi]) and 167 patients (50% receiving BTKi), respectively. Of the 14 CIRS organ systems, three had a strong and stable influence on EFS: any vascular, moderate/severe endocrine, moderate/severe upper gastrointestinal comorbidity. These were combined to create the CLL-CI score, which was categorized into 3 risk groups. In the derivation dataset, the median EFS was 58, 33, and 20 months in the low, intermediate, and high risk groups, correspondingly. Two-year overall survival (OS) rates were 96%, 91%, and 82%. In the validation dataset, median EFS was 81, 40, and 23 months (two-year OS rates 97%/92%/88%), correspondingly. Adjusting for prognostic factors, CLL-CI was significantly associated with EFS in patients treated with either chemo-immunotherapy or with BTKi in each of our 2 datasets. CONCLUSIONS: The CLL-CI is a simplified, CLL-specific comorbidity index which can be easily applied in clinical practice and correlates with survival in CLL