Along with the proliferation of high-end and performant mobile devices, we find that the inclusion of visually animated user interfaces are commonplace, but that research on their performance is ...scarce. Thus, for this study, eight mobile apps have been developed for scrutiny and assessment to report on the device hardware impact and penalties caused by transitions and animations, with an emphasis on apps generated using cross-platform development frameworks. The tasks we employ for animation performance measuring, are those of (i) a complex animation consisting of multiple elements, (ii) the opening sequence of a side menu navigation pattern, and (iii) a transition animation during in-app page navigation. We employ multiple performance profiling tools, and scrutinize metrics including frames per second (FPS), CPU usage, device memory usage and GPU memory usage, all to uncover the impact caused by executing transitions and animations. We uncover important differences in device hardware utilization during animations across the different cross-platform technologies employed. Additionally, Android and iOS are found to differ greatly in terms of memory consumption, CPU usage and rendered FPS, a discrepancy that is true for both the native and cross-platform apps. The findings we report are indeed factors contributing to the complexity of app development.
Developing applications targeting mobile devices is a complex task involving numerous options, technologies, and trade-offs, mostly due to the proliferation and fragmentation of devices and ...platforms. As a result of this, cross-platform app development has enjoyed the attention of practitioners and academia for the previous decade. Throughout this review, we assess the academic body of knowledge and report on the state of research on the field. We do so with a particular emphasis on core concepts, including those of user experience, device features, performance, and security. Our findings illustrate that the state of research demand for empirical verification of an array of unbacked claims, and that a particular focus on qualitative user-oriented research is essential. Through our outlined taxonomy and state of research overview, we identify research gaps and challenges, and provide numerous suggestions for further research.
Purveyors of fine halos Koch-Hansen, Andreas J; Camilla Juul Hansen; Lombardo, Linda ...
Astronomy and astrophysics (Berlin),
01/2021, Letnik:
645
Journal Article
Recenzirano
Odprti dostop
Globular clusters (GCs) are important donors to the build-up of the Milky Way (MW) stellar halo, having contributed at the ten percent level over the Galactic history. Stars that originated from the ...second generation of dissolved or dissolving clusters can be readily identified via distinct light-element signatures such as enhanced N and Na and simultaneously depleted C and O abundances. In this paper we present an extensive chemical abundance analysis of the halo star J110842, which was previously kinematically associated with the massive MW GC ω Centauri (ωCen), and we discuss viable scenarios from escape to encounter. Based on a high-resolution, high signal-to-noise spectrum of this star using the UVES spectrograph, we were able to measure 33 species of 31 elements across all nucleosynthetic channels. The star’s low metallicity of Fe II/H = −2.10 ± 0.02(stat.) ± 0.07(sys.) dex places it in the lower sixth percentile of ωCen’s metallicity distribution. We find that all of the heavier-element abundances, from α- and Fe-peak elements to neutron-capture elements are closely compatible with ωCen’s broad abundance distribution. However, given the major overlap of this object’s abundances with the bulk of all of the MW components, this does not allow for a clear-cut distinction of the star’s origin. In contrast, our measurements of an enhancement in CN and its position on the Na-strong locus of the Na-O anticorrelation render it conceivable that it originally formed as a second-generation GC star, lending support to a former association of this halo star with the massive GC ωCen.
Abstract
The interpretation of potentially new and already known stellar structures located at low latitudes is hindered by the presence of dense gas and dust, as observations toward these sight ...lines are limited. We have identified Apache Point Observatory Galaxy Evolution Experiment (APOGEE) stars belonging to the low-latitude globular clusters 2MASS-GC02 and Terzan 4, presenting the first chemical element abundances of stars residing in these poorly studied clusters. As expected, the signature of multiple populations coexisting in these metal-rich clusters is evident. We redetermine the radial velocity of 2MASS-GC02 to be −87 ± 7 km s
−1
, finding that this cluster’s heliocentric radial velocity is offset by more than 150 km s
−1
from the literature value. We investigate a potentially new low-latitude stellar structure and a kiloparsec-scale nuclear disk (or ring) that has been put forward to explain a high-velocity (
V
GSR
∼ 200 km s
−1
) peak reported in several Galactic bulge fields based on the APOGEE commissioning observations. New radial velocities of field stars at (
l
,
b
) = (−6°,0 °) are presented and combined with the APOGEE observations at negative longitudes to carry out this search. Unfortunately no prominent −200 km s
−1
peak at negative longitudes along the plane of the Milky Way are apparent, as predicted for the signature of a nuclear feature. The distances and Gaia EDR3 proper motions of the high-
V
GSR
stars do not support the current models of stars on bar-supporting orbits as an explanation of the +200 km s
−1
peak.
Abstract Aim Explore, understand and address issues that impact upon timely and adequate allocation of prehospital medical assistance and resources to out-of-hospital cardiac arrest (OHCA) patients. ...Methods Mixed-methods: design obtaining data for one year in three emergency medical communication centres (EMCC); Oslo-Akershus (OA), Vestfold-Telemark (VT) and Østfold (Ø). Data collection included quantitative data from analysis of dispatch logs, ambulance records and audio files. Qualitative data were collected through in-depth interviews and non-participant observations. Results OA-, VT- and Ø-EMCC responded to 1095 OHCAs and 579 of these calls were included for further analysis (333, 143 and 103, respectively). There were significant site differences in their recognition of OHCA (89, 94 and 78%, respectively, p < 0.001), provision of CPR instructions (83, 83 and 61%, respectively, p < 0.001), time from call answered to initial CPR instructions (1.4 min (1.2, 1.6), 1.1 min (0,9, 1.2) and 1.3 (1.2, 1.7) respectively, p = 0.002). The most frequent reason for delayed or failed recognition of OHCA was misinterpretation of agonal breathing. Interviews and observations revealed individual differences in protocol use, interrogation strategy and assessment of breathing. Use of protocol was only part of decision making, dispatchers trusted their own clinical experience and intuition, and used assumptions about the patient and the situation as part of decision making. Conclusion Agonal breathing continues to be the main barrier to recognition of cardiac arrest. Individual differences among dispatchers’ strategies can directly impact on performance, mainly due to the wide definition of cardiac arrest and lack of uniform tools for assessment of breathing.
ABSTRACT
We present photometric metallicity measurements for a sample of 2.6 million bulge red clump stars extracted from the Blanco DECam Bulge Survey (BDBS). Similar to previous studies, we find ...that the bulge exhibits a strong vertical metallicity gradient, and that at least two peaks in the metallicity distribution functions appear at b < −5°. We can discern a metal-poor (Fe/H ∼ −0.3) and metal-rich (Fe/H ∼ +0.2) abundance distribution that each show clear systematic trends with latitude, and may be best understood by changes in the bulge’s star formation/enrichment processes. Both groups exhibit asymmetric tails, and as a result we argue that the proximity of a star to either peak in Fe/H space is not necessarily an affirmation of group membership. The metal-poor peak shifts to lower Fe/H values at larger distances from the plane while the metal-rich tail truncates. Close to the plane, the metal-rich tail appears broader along the minor axis than in off-axis fields. We also posit that the bulge has two metal-poor populations – one that belongs to the metal-poor tail of the low latitude and predominantly metal-rich group, and another belonging to the metal-poor group that dominates in the outer bulge. We detect the X-shape structure in fields with |Z| > 0.7 kpc and for stars with Fe/H > −0.5. Stars with Fe/H < −0.5 may form a spheroidal or ‘thick bar’ distribution while those with Fe/H $\gtrsim$ −0.1 are strongly concentrated near the plane.
Abstract
We present wide-field, high resolution maps of the color excess for 14 globular clusters toward the Southern Galactic bulge. The maps were derived using Gaia EDR3 astrometry and stellar ...photometry from the Blanco DECam Bulge Survey, which is a deep, wide-field
ugriz
Y photometric survey of the southern Galactic bulge. Comparisons with WISE 12
μ
m images of thermal continuum emission demonstrate that the maps presented here trace interstellar extinction by dust down to 5″ scales. We use the reddening-corrected photometry of proper motion-selected cluster stars to build color–magnitude diagrams for the target globular clusters, which show residual broadening in excess of that expected from the photometric errors alone. This residual broadening is likely to be driven by star-to-star elemental abundance variations.
The noncovalent interactions between azides and oxygen‐containing moieties are investigated through a computational study based on experimental findings. The targeted synthesis of organic compounds ...with close intramolecular azide–oxygen contacts yielded six new representatives, for which X‐ray structures were determined. Two of those compounds were investigated with respect to their potential conformations in the gas phase and a possible significantly shorter azide–oxygen contact. Furthermore, a set of 44 high‐quality, gas‐phase computational model systems with intermolecular azide–pnictogen (N, P, As, Sb), –chalcogen (O, S, Se, Te), and –halogen (F, Cl, Br, I) contacts are compiled and investigated through semiempirical quantum mechanical methods, density functional approximations, and wave function theory. A local energy decomposition (LED) analysis is applied to study the nature of the noncovalent interaction. The special role of electrostatic and London dispersion interactions is discussed in detail. London dispersion is identified as a dominant factor of the azide–donor interaction with mean London dispersion energy‐interaction energy ratios of 1.3. Electrostatic contributions enhance the azide–donor coordination motif. The association energies range from −1.00 to −5.5 kcal mol−1.
The interactions that bind: The noncovalent interactions between azides and oxygen‐containing moieties are investigated through a computational study based on experimental findings. A set of 44 high‐quality, gas‐phase computational model systems with intermolecular azide–pnictogen, –chalcogen, and –halogen contacts are compiled and investigated through semiempirical quantum mechanical methods, density functional approximations, and wave function theory.
This review covers a family of atomistic, mostly quantum chemistry (QC) based semiempirical methods for the fast and reasonably accurate description of large molecules in gas and condensed phase. The ...theory is derived from a density functional (DFT) perturbation expansion of the electron density in fluctuation terms to various orders similar to the original density functional tight binding model. The term “eXtended” in their name (xTB) emphasizes the parameter availability for almost the entire periodic table of elements (Z ≤ 86) and improvements of the underlying theory regarding, for example, the atomic orbital basis set, the level of multipole approximation and the treatment of the important electrostatic and dispersion interactions. A common feature of most members is their consistent parameterization on accurate gas phase theoretical reference data for geometries, vibrational frequencies and noncovalent interactions, which are the primary properties of interest in typical applications to systems composed of up to a few thousand atoms. Further specialized versions were developed for the description of electronic spectra and corresponding response properties. Besides a provided common theoretical background with some important implementation details in the efficient and free xtb program, various benchmarks for structural and thermochemical properties including (transition‐)metal systems are discussed. The review is completed by recent extensions of the model to the force‐field (FF) level as well as its application to solids under periodic boundary conditions. The general applicability together with the excellent cost‐accuracy ratio and the high robustness make the xTB family of methods very attractive for various fields of computer‐aided chemical research.
This article is categorized under:
Electronic Structure Theory > Ab Initio Electronic Structure Methods
Electronic Structure Theory > Semiempirical Electronic Structure Methods
Software > Quantum Chemistry
The geometry, frequency, and noncovalent interaction parametrization of the extended tight binding Hamiltonian provides an essential tool for computational modeling, most prominently to explore the potential energy landscape in multilevel modeling workflows.
Abstract
We present photometric evidence for multiple stellar populations (MPs) in 14 globular clusters (GCs) toward the southern Galactic bulge. The photometric data come as part of the Blanco DECam ...Bulge Survey, which is a deep, wide-field near-UV-near-IR (
ugriz
Y) survey of the southern Galactic bulge. Here, we present the first systematic study of bulge GC multiple populations with deep photometry including the
u
band, which is a crucial indicator of the abundance of CNO-bearing molecules in stellar atmospheres. We identify cluster members using Gaia EDR3 proper motion measurements, and then isolate red giant branch stars using
r
versus
u
−
r
color–magnitude diagrams. We find evidence suggesting all 14 clusters host at least two populations, and NGC 6441, NGC 6626, and NGC 6656 appear to have at least three populations. Many of these clusters are not part of the Hubble Space Telescope (HST) surveys nor do they have comprehensive spectroscopic analyses so we are presenting the first evidence of MPs in several clusters. Not only do we find a strong anticorrelation between the fraction of first-generation stars and cluster absolute
V
magnitude, but the correlation coefficient and cluster-to-cluster scatter are similar to the results obtained from HST. Our ground-based data extend to much larger radial distances than similar HST observations, enabling a reliable estimate of the global fraction of first-generation stars in each cluster. This study demonstrates that ground-based
u
-band photometry as provided by DECam will prove powerful in the study of multiple populations in resolved GCs.
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