We present a homogeneous catalog of 275 large (effective radius 5 3) ultra-diffuse galaxy (UDG) candidates lying within an 290 square degree region surrounding the Coma Cluster. The catalog results ...from our automated postprocessing of data from the Legacy Surveys, a three-band imaging survey covering 14,000 square degrees of the extragalactic sky. We describe a pipeline that identifies UDGs and provides their basic parameters. The survey is as complete in these large UDGs as previously published UDG surveys of the central region of the Coma Cluster. We conclude that the majority of our detections are at roughly the distance of the Coma Cluster, implying effective radii ≥2.5 kpc, and that our sample contains a significant number of analogs of DF44, where the effective radius exceeds 4 kpc, both within the cluster and in the surrounding field. The g − z color of our UDGs spans a large range, suggesting that even large UDGs may reflect a range of formation histories. A majority of the UDGs are consistent with being lower stellar mass analogs of red sequence galaxies, but we find both red and blue UDG candidates in the vicinity of the Coma Cluster and a relative overabundance of blue UDG candidates in the lower-density environments and the field. Our eventual processing of the full Legacy Surveys data will produce the largest, most homogeneous sample of large UDGs.
Metabotropic glutamate receptors (mGluRs) are mandatory dimers playing important roles in regulating CNS function. Although assumed to form exclusive homodimers, 16 possible heterodimeric mGluRs have ...been proposed but their existence in native cells remains elusive. Here, we set up two assays to specifically identify the pharmacological properties of rat mGlu heterodimers composed of mGlu2 and 4 subunits. We used either a heterodimer-specific conformational LRET-based biosensor or a system that guarantees the cell surface targeting of the heterodimer only. We identified mGlu2-4 specific pharmacological fingerprints that were also observed in a neuronal cell line and in lateral perforant path terminals naturally expressing mGlu2 and mGlu4. These results bring strong evidence for the existence of mGlu2-4 heterodimers in native cells. In addition to reporting a general approach to characterize heterodimeric mGluRs, our study opens new avenues to understanding the pathophysiological roles of mGlu heterodimers.
High-flux filtration membranes constructed through scalable and sustainable methods are desirable for energy-efficient separations. Often, these criteria are difficult to be reconciled with one ...another. Polymeric membranes can provide high flux but frequently involve organic solvents in processing steps. Solubility of many polymeric membranes in organic media also restricts their implementation in solvent filtration. In the present work, we report a simple and high-throughput aqueous processing approach for polyelectrolyte complex (PEC) membranes with controllable porosity and stability in various aqueous and organic environments. PECs are materials composed of oppositely charged polymer chains that can form solids in aqueous environments, yet which can be dissolved in very specific salt solutions capable of breaking the interpolymer ion pairs. By exploiting the salt-induced dissolution and subsequent reformation of the complex, nano- to microporous films are rapidly synthesized which resemble membranes obtained through conventional solvent-phase inversion techniques. PECs remain stable in organic solvents because of the low dielectric constant of the environment, which enhances electrostatic interactions, making them suitable for a wide range of water and solvent filtration applications. Here, we elucidate how the polymer-phase behavior can be manipulated to exercise morphological control, test membrane performance for water and solvent filtration, and quantify the mechanical stability of PECs in relevant conditions.
ABSTRACT We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10 4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy ( V = 24.8 mag arcsec−2), ...found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (Re(V) = 12″) and proximity (15′) to the well-known dwarf spheroidal galaxy And II. Its red color (V − I = 1.0), shallow Sérsic index (nV = 0.68), and the absence of detectable H emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6 m telescope (Vh = 5450 40 km s−1) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (∼78 Mpc), DGSAT I would have an Re ∼ 4.7 kpc and MV ∼ −16.3. Its properties resemble those of the ultra-diffuse galaxies (UDGs) recently discovered in the Coma cluster. DGSAT I is the first case of these rare UDGs found in this galaxy cluster. Unlike the UDGs associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.
The treatment of thrombosis in patients with antiphospholipid syndrome (APS) usually requires long-term anticoagulation with vitamin K antagonists. The effectiveness of direct oral anticoagulants ...(DOACs) in APS has not been fully addressed. The purpose of this research was to analyze the efficacy (thrombotic event–free time) and tolerability (bleeding events) of DOACs in patients with APS.
We performed a descriptive analysis of a systematic review of data from patients with APS treated with DOACs reported in the literature, via EMBASE, PubMed, and the European League Against Rheumatism and American College of Rheumatology congresses. After systematic review, a meta-analysis of data from clinical trials was performed.
A total of 728 patients, accounting for 731 courses of treatment with DOACs, were identified. The majority (48.3%) presented with triple anti-phospholipid antibody positivity. The prevalence of thrombosis during DOAC treatment was 13.9%. Analysis of risk factors for recurrent thrombosis suggested that a higher mean (SD) number of prior thrombotic events (1.80 0.87 vs 1.67 1.45; P = 0.012), history of combined arterial and venous thrombosis (27.3% vs 9.2% P < 0.0001; odds ratio OR = 3.72 95% CI, 1.91–7.25), previous treatment with LMWH (9.8% vs 1.1% P = 0.04; OR = 9.95 95% CI, 1.08–91.97), use of immunosuppressant treatment (41.7% vs 12.7% P = 0.03; OR = 4.9 95% CI, 1.21–19.76), and no reason to switch anticoagulant treatment other than patient's decision (32% vs 2.8% P = 0.001; OR = 16.24 95% CI, 3.16–83.52) were associated with a high risk for re-thrombosis. Meta-Analysis did not show statistically relevant difference in risk of thrombosis or bleeding comparing warfarin with DOACs.
The findings from this systematic literature review and meta-analysis suggest that patients treated with DOACs and having risk factors such as history of recurrent thrombosis, a history of combined arterial and venous thrombosis, or a need for immunosuppressant treatment, may have higer ratio of thrombotic recurrence. There are limited data to inform decisions on the use of DOACs in patients with APS with different or no risk factors.
Display omitted
Summary This survey gives an overview of Monte Carlo methodologies using surrogate models, for dealing with densities that are intractable, costly, and/or noisy. This type of problem can be found in ...numerous real‐world scenarios, including stochastic optimisation and reinforcement learning, where each evaluation of a density function may incur some computationally‐expensive or even physical (real‐world activity) cost, likely to give different results each time. The surrogate model does not incur this cost, but there are important trade‐offs and considerations involved in the choice and design of such methodologies. We classify the different methodologies into three main classes and describe specific instances of algorithms under a unified notation. A modular scheme that encompasses the considered methods is also presented. A range of application scenarios is discussed, with special attention to the likelihood‐free setting and reinforcement learning. Several numerical comparisons are also provided.
Abstract
This paper presents a theoretical investigation of the polarization and magnetic sensitivity of the near-ultraviolet (near-UV) solar spectral lines of Fe
ii
between 250 and 278 nm. In recent ...years, UV spectropolarimetry has become key to uncovering the magnetism of the upper layers of the solar chromosphere. The unprecedented data obtained by the CLASP2 suborbital space experiment across the Mg
ii
h and k lines around 280 nm are a clear example of the capabilities of near-UV spectropolarimetry for magnetic field diagnostics throughout the whole solar chromosphere. Recent works have pointed out the possible complementary diagnostic potential of the many Fe
ii
lines in the unexplored spectral region between 250 and 278 nm, but no quantitative analysis of the polarization and magnetic sensitivity of those spectral lines has been carried out yet. To study the polarization signals in these spectral lines, we create a comprehensive atomic model including all the atomic transitions resulting in strong spectral lines. We then study the magnetic sensitivity of the linear and circular polarization profiles in a semiempirical model representative of the quiet Sun. We present a selection of Fe
ii
spectral lines with significant linear and circular polarization signals and evaluate their diagnostic capabilities by studying their formation heights and magnetic sensitivity through the action of the Hanle and Zeeman effects. We conclude that when combined with the CLASP2 spectral region these Fe
ii
lines are of interest for the inference of magnetic fields throughout the solar chromosphere, up to near the base of the corona.
ABSTRACT We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using a low cost telephoto lens with a wide field of view to explore stellar substructure in the ...outskirts of the stellar disk of the LMC (<10° from the LMC center). These data have higher resolution than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in the northern periphery, with no comparable counterparts in the south. We compare these data to detailed simulations of the LMC disk outskirts, following interactions with its low mass companion, the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field. The simulations are used to assess the origin of the northern structures, including also the low density stellar arc recently identified in the Dark Energy Survey data by Mackey et al. at ∼15°. We conclude that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to constrain the LMC's interaction history with and impact parameter of the SMC. More generally, we find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for 1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are driven by dwarf-dwarf interactions.
Tracing satellite planes in the Sculptor group Martínez-Delgado, David; Makarov, Dmitry; Javanmardi, Behnam ...
Astronomy and astrophysics (Berlin),
08/2021, Letnik:
652
Journal Article
Recenzirano
Odprti dostop
Context.
In recent years, a new generation of large-scale imaging surveys have probed wide field regions for the first time around some nearby galaxies in an unprecedentedly low surface-brightness ...regime (∼28.0−29.0 mag arcsec
−2
). This provides the chance to discover very faint dwarf satellites by means of systematic visual inspection of these public deep images.
Aims.
In this paper, we report the first results of a systematic survey of faint dwarf spheroidal galaxies in the vicinity of the bright late-type spiral galaxy NGC 253 by means of a visual inspection of the images taken by the Dark Energy Survey.
Methods.
We performed a new NGC 253 satellite search using co-added image cutouts reprocessed in the DESI Legacy image surveys. We used
GALFIT
software to investigate the photometric and structural properties of three dwarf galaxies.
Results.
We report the discovery of three new dwarf galaxies in the vicinity of the brightest member of the Sculptor filament, the late-type spiral NGC 253, located at a distance of 3.7 Mpc towards Anti-Virgo. We name them Do II, Do III, and Do IV. Assuming they are companions of NGC 253, their total absolute
V
-magnitudes fall in the −7 to −9 mag range, which is typical for dwarf satellites in the local Universe. The central surface brightness tends to be extremely low for all three discovered dwarfs and falls roughly in the range of 25−26 mag arcsec
−2
in
g
-band. Using known data on distances and velocities of galaxies, we estimate the total virial mass of the NGC 253 group to be 8 × 10
11
M
⊙
, which gives a virial radius of
R
200
= 186 kpc and a turn-around radius of 706 kpc. We also discuss the possible existence of a spatially flattened and velocity-correlated satellite system around NGC 253. This large-scale structure is orientated almost edge-on to the line of sight. The possible plane of satellites is only 31 kpc thick with a minor-to-major axis ratio of 0.14. Four out of five galaxies with measured velocities follow a common velocity trend similar to those observed in the planes of satellites around the Andromeda and Centaurus A galaxies. However, the small number of galaxies with known velocities prevents us from reaching a definitive conclusion about the formation scenario of the structure and its possible relation to the surrounding cosmic web.
PDF
