The Einstein equivalence principle (EEP) has a central role in the understanding of gravity and space-time. In its weak form, or weak equivalence principle (WEP), it directly implies equivalence ...between inertial and gravitational mass. Verifying this principle in a regime where the relevant properties of the test body must be described by quantum theory has profound implications. Here we report on a novel WEP test for atoms: a Bragg atom interferometer in a gravity gradiometer configuration compares the free fall of rubidium atoms prepared in two hyperfine states and in their coherent superposition. The use of the superposition state allows testing genuine quantum aspects of EEP with no classical analogue, which have remained completely unexplored so far. In addition, we measure the Eötvös ratio of atoms in two hyperfine levels with relative uncertainty in the low 10
, improving previous results by almost two orders of magnitude.
Context.
Abundances of beryllium in metal-poor stars scale linearly with metallicity down to Fe/H ∼ −3.0. In the stars where Be has been detected at this extremely metal-poor regime, an increased ...abundance scatter has been previously reported in the literature. This scatter could indicate a flattening of the relation between Be abundances and metallicity.
Aims.
Our aim is to perform a new investigation of Be abundances in extremely metal-poor stars and try to clarify whether a Be abundance plateau exists. We revisited the Be abundances in a sample of nine dwarfs with metallicities close to Fe/H ∼ −3.0. Additionally, we analysed the Be lines in the spectra of stars BPS BS 16968-0061 and CD-33 1173 for the first time.
Methods.
We took advantage of
Gaia
DR2 parallaxes to refine values of the surface gravity of the stars. Updated values of surface gravity can have a significant impact on the determination of Be abundances. The other atmospheric parameters were computed using photometric and spectroscopic data. Abundances of Be were determined using spectrum synthesis and model atmospheres.
Results.
Some of the stars indeed suggest a flattening. Over about a 0.5 dex range in metallicity, between Fe/H ∼ −2.70 and −3.26, the Be abundances stay mostly constant at about log(Be/H) ∼ −13.2 dex. Nevertheless, for several stars, we could only place upper limits that are below that level. Most of the sample stars are consistent with having been formed at the progenitor of the so-called
Gaia
-Enceladus merger. Two out of the three stars likely formed in-situ are the ones that deviate the most from the linear relation.
Conclusions.
The mixed origin of these extremely metal-poor stars offers a clue to understanding the flattening. We suggest that our observations can be naturally understood as a consequence of the inhomogeneous star forming conditions in the early Galaxy. Without efficient mixing, the early interstellar medium would be characterised by a large scatter in Fe abundances at a given moment. Beryllium, on the other hand, because of its origins in cosmic-ray spallation, would have more homogeneous abundances (in a Galaxy-wide sense). We therefore suggest that the observed flattening of the Be-versus-metallicity relation reflects a stronger scatter in the Galactic Fe abundances at a given age.
We show the opportunity for tuning of the spectral position of the Mn4+ red emission in the series of double perovskites, Ba2LaNbO6:Mn4+, Ba2La(Nb0.8,Zr0.1,W0.1)O6:Mn4+, and Ba2La(Zr0.5,W0.5)O6:Mn4+ ...with increasing chemically induced symmetry disturbance. Such a disorder appeared attractive to engineering phosphors for pressure sensors or horticultural applications, for instance. The goal of the present research, not yet systematically addressed in the literature, was to unveil the correlation between chemically induced controlled crystal lattice distortion and the luminescence of Mn4+. For this purpose, the luminescence of these phosphors was methodically investigated at different pressures and temperatures. A pressure-induced redshift of photoluminescent lines with the rate of − 4 cm−1/kbar was found within the 0–230 kbar range, and the emission peak moved from 685 to 740 nm then. Furthermore, the cationic disorder allowed tuning of the Mn4+ luminescence making it useful for horticultural applications with a better fit between the emission wavelength and the strong chlorophyll absorption in the deep red part of the spectrum. The Mn4+ energy levels were computationally determined using the exchange charge model of the crystal-field theory which allowed for a deeper understanding of the experimental results. We found a correlation between the introduced disorder of the cationic subsystem and the energy of the Mn4+ emitting 2Eg level (R-line) as well as its intensity. This research brought a deeper understanding of the Mn4+-activated phosphors and, in turn, provides tips for a prudent search of materials for advanced practical uses.
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•The Ba2La(Nb1–2xZrxWx)O6:Mn (x = 0;x = 0.1;x = 0.5) isostructural phosphors are reported.•The influence of pressure and temperature on the luminescence of Mn4+ is presented.•Effects of chemically induced partial cation substitution are investigated.•Theoretical studies support the understanding of the experimental dependencies.•The findings provide tips for a deliberate design of phosphors for advanced uses.
ABSTRACT We present X-ray source catalogs for the 7 Ms exposure of the Chandra Deep Field-South (CDF-S), which covers a total area of 484.2 arcmin2. Utilizing wavdetect for initial source detection ...and ACIS Extract for photometric extraction and significance assessment, we create a main source catalog containing 1008 sources that are detected in up to three X-ray bands: 0.5-7.0 keV, 0.5-2.0 keV, and 2-7 keV. A supplementary source catalog is also provided, including 47 lower-significance sources that have bright ( ) near-infrared counterparts. We identify multiwavelength counterparts for 992 (98.4%) of the main-catalog sources, and we collect redshifts for 986 of these sources, including 653 spectroscopic redshifts and 333 photometric redshifts. Based on the X-ray and multiwavelength properties, we identify 711 active galactic nuclei (AGNs) from the main-catalog sources. Compared to the previous 4 Ms CDF-S catalogs, 291 of the main-catalog sources are new detections. We have achieved unprecedented X-ray sensitivity with average flux limits over the central 1 arcmin2 region of 1.9 × 10−17, 6.4 × 10−18, and 2.7 × 10−17 erg cm−2 s−1 in the three X-ray bands, respectively. We provide cumulative number-count measurements observing, for the first time, that normal galaxies start to dominate the X-ray source population at the faintest 0.5-2.0 keV flux levels. The highest X-ray source density reaches 50,500 deg−2, and 47% 4% of these sources are AGNs ( 23,900 deg−2).
Mixed LuxY1-xVO4 crystals, undoped and doped with Eu3+, were synthetized by the solid state reaction method. The crystal structure and phase composition were controlled by the X-ray diffraction ...(XRD), Raman analysis, and scanning electron microscope (SEM) measurements. The samples' crystallinity was improved by annealing. Nevertheless, the lattice distortion caused by the substitution of Y by Lu was detected. The lattice parameters derived from the XRD data are in good agreement with the calculated ones. It was found that the luminescence intensity increase in the annealed samples is related to the improvement of crystallinity of samples. According to the studies of X-ray excited luminescence at 300K the relative luminescence intensity increases for the samples with intermediate values of x. For the LuxY1-xVO4:Eu3+ the highest luminescence intensity was detected for x=0.7 and ascribed to the effect of decrease of the mean distance between the thermalized electrons and holes. For the undoped crystals the luminescence is partially quenched at 300K, however the sample with x=0.7 demonstrate highest intensity as well. The effect in the undoped samples is due to the increase of the temperature of luminescence quenching in samples with intermediate values of x.
Severe foot and ankle injuries are complex and challenging to treat, often requiring multiple operations to salvage the limb contributing to a prolonged healing period. There is some evidence to ...suggest that early amputation for some patients may result in better long-term outcomes than limb salvage. The challenge is to identify the regional injury burden for an individual that would suggest a better outcome with an amputation. The OUTLET study is a prospective, multicenter observational study comparing 18-month outcomes after limb salvage versus early amputation among patients aged 18-60 years with severe distal tibia, ankle, and foot injuries. This study aims to build upon the previous work of the Lower Extremity Assessment Project by identifying the injury and patient characteristics that help define a subgroup of salvage patients who will have better outcomes had they undergone a transtibial amputation.
Micronuclei (MN) form from missegregated chromatin that recruits its own nuclear envelope during mitotic exit and are a common consequence of chromosomal instability. MN are unstable due to errors in ...nuclear envelope organization and frequently rupture, leading to loss of compartmentalization, loss of nuclear functions, and major changes in genome stability and gene expression. However, recent work found that, even prior to rupture, nuclear processes can be severely defective in MN, which may contribute to rupture-associated defects and have lasting consequences for chromatin structure and function. In this review we discuss work that highlights nuclear function defects in intact MN, including their mechanisms and consequences, and how biases in chromosome missegregation into MN may affect the penetrance of these defects. Illuminating the nuclear environment of MN demonstrates that MN formation alone has major consequences for both the genome and cell and provides new insight into how nuclear content is regulated.
We exploit the 7 Ms Chandra observations in the Chandra Deep Field-South (CDF-S), the deepest X-ray survey to date, coupled with CANDELS/GOODS-S data, to measure the total X-ray emission arising from ...2076 galaxies at 3.5 ≤ z < 6.5. This aim is achieved by stacking the Chandra data at the positions of optically selected galaxies, reaching effective exposure times of ≥109s. We detect significant (>3.7σ) X-ray emission from massive galaxies at z ≈ 4. We also report the detection of massive galaxies at z ≈ 5 at a 99.7 per cent confidence level (2.7σ), the highest significance ever obtained for X-ray emission from galaxies at such high redshifts. No significant signal is detected from galaxies at even higher redshifts. The stacking results place constraints on the BHAD associated with the known high-redshift galaxy samples, as well as on the SFRD at high redshift, assuming a range of prescriptions for X-ray emission due to X- ray binaries. We find that the X-ray emission from our sample is likely dominated by processes related to star formation. Our results show that low-rate mass accretion on to SMBHs in individually X-ray-undetected galaxies is negligible, compared with the BHAD measured for samples of X-ray detected AGN, for cosmic SMBH mass assembly at high redshift. We also place, for the first time, constraints on the faint-end of the AGN X-ray luminosity function (logLX ∼ 42) at z > 4, with evidence for fairly flat slopes. The implications of all of these findings are discussed in the context of the evolution of the AGN population at high redshift.
Abstract
The ground-based gamma-ray observatory Very Energetic Radiation Imaging Telescope Array System (VERITAS,
https://veritas.sao.arizona.edu/
) is sensitive to photons of astrophysical origin ...with energies in the range between ≈85 GeV and ≈30 TeV. The instrument consists of four 12 m diameter imaging Cherenkov telescopes operating at the Fred Lawrence Whipple Observatory in southern Arizona. VERITAS started four-telescope operations in 2007 and collects about 1100 hr of good-weather data per year. The VERITAS collaboration has published over 100 journal articles since 2008 reporting on gamma-ray observations of a large variety of objects: Galactic sources like supernova remnants, pulsar wind nebulae, and binary systems; extragalactic sources like star-forming galaxies, dwarf-spheroidal galaxies, and highly variable active galactic nuclei. This note presents VTSCat: the catalog of high-level data products from all VERITAS publications.
Measuring the density and velocity of fluids is one of the important tasks in oil and petroleum industries. The article demonstrates the measurements of these parameters precisely for different ...fluids and various diameters of pipes by using radiotracer injection and Artificial Neural Network (ANN). The required data for training and testing the ANN model were obtained by the MCNPX code simulations. Before using the simulation results for training the ANN, simulation geometry was validated with an experimental setup. The experimental setup consists of two 2-inch NaI(Tl) detectors that are positioned in distance of 120 mm from each other and one 133Ba radioactive source as a tracer. It is shown that the estimated Mean Relative Error (MRE) of the density determination in presented system was less than 0.9%. The relative combined standard uncertainty of the fluid velocity measurement did not exceed 0.5%.
•A system was proposed to measure both density and velocity of fluids, simultaneously.•Dynamic condition was produced using combination of MATLAB and MCNPX code.•The simulation results were validated using experimental results.•MRE of the density determination was less than 0.9%.•Relative combined standard uncertainty of velocity measurement didn’t exceed 0.5%.
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