Active galactic nuclei (AGNs) that show strong rest-frame optical/UV variability in their blue continuum and broad line emission are classified as changing-look AGN, or at higher luminosities, ...changing-look quasars (CLQs). These surprisingly large and sometimes rapid transitions challenge accepted models of quasar physics and duty cycles, offer several new avenues for study of quasar host galaxies, and open a wider interpretation of the cause of differences between broad and narrow-line AGN. To better characterize extreme quasar variability, we present follow-up spectroscopy as part of a comprehensive search for CLQs across the full Sloan Digital Sky Survey (SDSS) footprint using spectroscopically confirmed quasars from the SDSS DR7 catalog. Our primary selection requires large-amplitude ( mag, mag) variability over any of the available time baselines probed by the SDSS and Pan-STARRS 1 surveys. We employ photometry from the Catalina Sky Survey to verify variability behavior in CLQ candidates where available, and confirm CLQs using optical spectroscopy from the William Herschel, MMT, Magellan, and Palomar telescopes. For our adopted signal-to-noise ratio threshold on variability of broad Hβ emission, we find 17 new CLQs, yielding a confirmation rate of 20%. These candidates are at lower Eddington ratio relative to the overall quasar population, which supports a disk-wind model for the broad line region. Based on our sample, the CLQ fraction increases from 10% to roughly half as the continuum flux ratio between repeat spectra at 3420 increases from 1.5 to 6. We release a catalog of more than 200 highly variable candidates to facilitate future CLQ searches.
PURPOSE OF REVIEWPlacebo-controlled randomized trials have demonstrated the efficacy of clopidogrel in combination with aspirin across a broad range of clinical presentations. Recent trials have ...addressed several remaining issues regarding clopidogrel therapy.
RECENT FINDINGSThree randomized trials examined the role of platelet function testing (PFT) in clopidogrel-treated patients. The results do not support the use of PFT to adjust clopidogrel dose after percutaneous coronary intervention (PCI), particularly in patients with stable angina or ischemia, in whom event rates are low irrespective of on-treatment reactivity. Doses greater than clopidogrel 150 mg daily are required to sufficiently overcome high reactivity in CYP2C19 loss-of-function (LOF) allele carriers. Clopidogrel response variability also influences the time to platelet recovery after drug discontinuation, and a proof-of-principle study supports the concept of using PFT for surgical timing. Unlike its efficacy in the setting of acute coronary syndrome (ACS) and PCI, prasugrel was not superior to clopidogrel in medically treated patients recovering from ACS.
SUMMARYCurrent data do not support routine PFT to guide antiplatelet therapy in patients undergoing nonurgent PCI. The role of PFT to optimize therapy in ACS patients remains unaddressed, and further study is needed to confirm its promise in guiding surgical timing in patients who have discontinued therapy. Clopidogrel remains an important therapeutic option for patients presenting after an ACS who did not undergo initial revascularization.
An amine transaminase was engineered for the efficient production of a chiral precursor to sacubitril, (2R,4S)-5-(1,1′-biphenyl-4-yl)-4-amino-2-methylpentanoic acid, a key component in the ...blockbuster heart failure drug Entresto. Starting from an enzyme with trace activity and preference for the undesired diastereoisomer, 11 rounds of enzyme evolution were performed. The resultant variant, CDX-043, showed high productivity giving 90% conversion at 75 g/L substrate concentration with 1% enzyme loading with respect to the substrate in 24 h and without the use of an organic cosolvent. The product diastereomeric purity toward the desired (2R,4S)-stereoisomer was >99.9:0.1 d.r. This variant also exhibited high process robustness and could tolerate reaction temperatures up to 65 °C, isopropylamine concentrations of at least 2 M, and reaction times of at least 5 days. A structural analysis of the enzyme variants gave insight into how the mutations affected activity and selectivity. This enzyme variant allows for the efficient and cost-effective production of sacubitril at large scale.
ABSTRACT
We investigate the responsiveness of the 2798 Å Mg ii broad emission line in active galactic nuclei (AGNs) on time-scales of several years. Our study is based on a sample of extremely ...variable AGNs as well as a broad population sample. The observed response of the line in previous studies has been mixed. By focusing on extreme variability (|Δg| > 1), we find that Mg ii clearly does respond to the continuum. However, the degree of responsiveness varies strikingly from one object to another: We see cases of Mg ii changing by as much as the continuum, more than the continuum, or very little at all. In 74 per cent of the highly variable sample, the behaviour of Mg ii corresponds with that of H β, with 30 per cent of the objects showing large variations in both lines. We do not detect any change in the line width that would correspond to broad-line region ‘breathing’, in accordance with results from the literature. Some of the objects in our highly variable sample show a clear asymmetry in the Mg ii profile. This skewness can be both to the blue and the red of the line centre. Results from our broad population sample show that highly variable quasars have lower Eddington ratios. This result holds for the variability of the continuum, but the correlation is significantly reduced for the variability of the Mg ii line. For the first time, we present an overview of the value of the intrinsic Baldwin effect for Mg ii in a large sample.
Coffee consumption is a regular part of daily life throughout the world. Research into the effects of coffee on human health is ongoing, but a recent study suggests that coffee and caffeine ...consumption can reduce the risk of elevated alanine aminotransferase activity in individuals at high risk for liver disease. This review will analyze the results of that study in light of the current literature.
The eROSITA upper limits Tubín-Arenas, Dusán; Krumpe, Mirko; Lamer, Georg ...
Astronomy and astrophysics (Berlin),
02/2024, Letnik:
682
Journal Article
Recenzirano
Odprti dostop
Context
. The soft X-ray instrument eROSITA on board the Spectrum-Roentgen-Gamma (SRG) observatory has successfully completed four of the eight planned all-sky surveys, detecting almost one million ...X-ray sources during the first survey (eRASS1). The catalog of this survey will be released as part of the first eROSITA data release (DR1).
Aims
. Based on X-ray aperture photometry, we provide flux upper limits for eRASS1 in several energy bands. We cover galactic longitudes between 180° ≲
l
≲ 360° (eROSITA-DE). These data are crucial for studying the X-ray properties of variable and transient objects, as well as non-detected sources in the eROSITA all-sky survey data.
Methods
. We performed aperture photometry on every pixel of the SRG/eROSITA standard pipeline data products for all available sky tiles in the single detection band (0.2–2.3 keV). Simultaneously, we performed the same analysis in the three-band detection at soft (0.2–0.6 keV), medium (0.6–2.3 keV), and hard (2.3–5.0 keV) energy bands. Based on the combination of products for the individual bands, we are also able to provide aperture photometry products and flux upper limits for the 0.2–5.0 keV energy band. The upper limits were calculated based on a Bayesian approach that utilizes detected counts and background within the circular aperture.
Results
. The final data products consist of tables with the aperture photometry products (detected counts, background counts, and exposure time), a close-neighbor flag, and the upper flux limit based on an absorbed power-law spectral model (Γ = 2.0,
N
H
= 3 × 10
20
cm
−2
). The upper limits are calculated using the one-sided 3
σ
confidence interval (CL) of a normal distribution, representing CL = 99.87%. The aperture photometry products allow for an easy computation of upper limits at any other confidence interval and spectral model. These data are stored in a database with hierarchical indexes in order to offer a fast query option.
Conclusions
. We provide a detailed description of the process of retrieving SRG/eROSITA upper limits for a large set of input positions, as well as of the eROSITA data, the X-ray aperture photometry, the upper limit calculation, and the final data products. The eROSITA upper flux limits represent either the maximum flux of potential non-detections or the 3
σ
upper flux uncertainty of detected sources. We emphasize the importance of choosing the right spectral model that ought to match the spectral shape of the source of interest: the wrong spectral model can produce discrepancies of up to 30% in the final flux upper limit value. We also describe the architecture of the database and the web tool, which are designed to handle large queries on input positions.
The eROSITA upper limits Tubín-Arenas, Dusán; Krumpe, Mirko; Lamer, Georg ...
Astronomy and astrophysics (Berlin),
02/2024, Letnik:
682
Journal Article
Recenzirano
Odprti dostop
Context. The soft X-ray instrument eROSITA on board the Spectrum-Roentgen-Gamma (SRG) observatory has successfully completed four of the eight planned all-sky surveys, detecting almost one million ...X-ray sources during the first survey (eRASS1). The catalog of this survey will be released as part of the first eROSITA data release (DR1). Aims. Based on X-ray aperture photometry, we provide flux upper limits for eRASS1 in several energy bands. We cover galactic longitudes between 180° ≲ l ≲ 360° (eROSITA-DE). These data are crucial for studying the X-ray properties of variable and transient objects, as well as non-detected sources in the eROSITA all-sky survey data. Methods. We performed aperture photometry on every pixel of the SRG/eROSITA standard pipeline data products for all available sky tiles in the single detection band (0.2–2.3 keV). Simultaneously, we performed the same analysis in the three-band detection at soft (0.2–0.6 keV), medium (0.6–2.3 keV), and hard (2.3–5.0 keV) energy bands. Based on the combination of products for the individual bands, we are also able to provide aperture photometry products and flux upper limits for the 0.2–5.0 keV energy band. The upper limits were calculated based on a Bayesian approach that utilizes detected counts and background within the circular aperture. Results. The final data products consist of tables with the aperture photometry products (detected counts, background counts, and exposure time), a close-neighbor flag, and the upper flux limit based on an absorbed power-law spectral model (Γ = 2.0, NH = 3 × 1020 cm−2). The upper limits are calculated using the one-sided 3σ confidence interval (CL) of a normal distribution, representing CL = 99.87%. The aperture photometry products allow for an easy computation of upper limits at any other confidence interval and spectral model. These data are stored in a database with hierarchical indexes in order to offer a fast query option. Conclusions. We provide a detailed description of the process of retrieving SRG/eROSITA upper limits for a large set of input positions, as well as of the eROSITA data, the X-ray aperture photometry, the upper limit calculation, and the final data products. The eROSITA upper flux limits represent either the maximum flux of potential non-detections or the 3σ upper flux uncertainty of detected sources. We emphasize the importance of choosing the right spectral model that ought to match the spectral shape of the source of interest: the wrong spectral model can produce discrepancies of up to 30% in the final flux upper limit value. We also describe the architecture of the database and the web tool, which are designed to handle large queries on input positions.
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