A class of hybrid compact star equations of state is investigated that joins by a Maxwell construction a low-density phase of hadronic matter, modeled by a relativistic mean-field approach with ...excluded nucleon volume, with a high-density phase of color superconducting two-flavor quark matter, described within a nonlocal covariant chiral quark model. It is found that the occurrence of a stable branch of hybrid compact stars requires a nonvanishing vector meson coupling in the quark model that exceeds a minimal value which depends on the presence of a diquark condensate. It is shown that these hybrid stars do not form a third family disconnected from the second family of ordinary neutron stars unless additional (de)confining effects are introduced with a density-dependent bag pressure. A suitably chosen density dependence of the vector meson coupling assures that at the same time the 2 M ⊙ maximum mass constraint is fulfilled on the hybrid star branch. A twofold interpolation method is realized which implements both the density dependence of a confining bag pressure at the onset of the hadron-to-quark matter transition and the stiffening of quark matter at higher densities by a density-dependent vector meson coupling. For three parametrizations of this class of hybrid equation of state the properties of corresponding compact star sequences are presented, including mass twins of neutron and hybrid stars at 2.00, 1.39 and 1.20 M ⊙ , respectively, and the hybrid compact star (third) families. The sensitivity of the hybrid equation of state and the corresponding compact star sequences to variations of the interpolation parameters at the 10% level is investigated and it is found that the feature of third family solutions for compact stars is robust against such a variation. This advanced description of hybrid star matter allows us to interpret GW170817 as a merger not only of two neutron stars but also of a neutron star with a hybrid star or of two hybrid stars.
Background
Oropharyngeal dysphagia (OD) is a prevalent poststroke condition with severe complications and increased mortality. Poststroke OD prevalence varies among studies and there is little ...evidence of its related risk factors and associated complications. Objective: to evaluate the prevalence of OD after stroke and the risk factors and associated complications.
Methods
We performed a prospective longitudinal study of stroke patients consecutively admitted to a general hospital. OD was diagnosed with the volume‐viscosity swallow test (V‐VST). Demographic, functional status and topographical and clinical variables of stroke were collected to assess risk factors for OD. We evaluated functional status, mortality, respiratory infections, and readmissions 3 and 12 months after stroke. A multivariate regression analysis determined associated risk factors for OD and for each outcome variable.
Key Results
We included 395 stroke patients with a 45.06% prevalence of OD on admission. OD was independently associated with age (OR = 1.05; CI = 1.02‐1.08), previous stroke (OR = 2.40; CI = 1.00‐5.79), severity using the National Institute of Health Stroke Scale (OR = 3.52; CI = 1.57‐7.87) and volume of the lesion (OR = 1.02; CI = 1.01‐1.03). OD after stroke was an independent risk factor for prolonged hospital stay (P = .049; β = 0.938) and institutionalization after discharge (OR = 0.47; CI = 0.24‐0.92); OD was an independent risk factor for poorer functional capacity (OR = 3.00; CI = 1.58‐5.68) and increased mortality (HR = 6.90; CI = 1.57‐30.34) 3 months after stroke.
Conclusions & Inferences
Poststroke OD is prevalent and associated with poor short and long term prognosis. Stroke severity and patient status before stroke were more relevant to OD than lesion location. Systematic screening programs and early OD management could significantly improve poststroke patient outcome.
Despite the high impact that OD has on stroke patient prognosis, poststroke dysphagia remains a neglected area of research. Our study had three main aims: to determine the prevalence of OD in acute stroke patients admitted to a general hospital; to establish socio‐demographic and clinical risk factors for poststroke OD, and to determine the impact of OD on the clinical outcome and 1‐year prognosis of the patient. We found a high prevalence (45.06%) of poststroke OD on admission. Older age, previous stroke diagnosis, severity of stroke according to NIHSS, and high stroke lesion volume were independent risk factors for OD development after a stroke. Moreover, we found that presenting OD after stroke was associated with high mortality rates during hospital stay and was an independent risk factor for prolonged length of hospital stay and institutionalization after hospital discharge; OD was also an independent risk factor for poorer functional capacity and increased risk of mortality 3 months after the stroke episode.
This paper analyzes the image of Israel, a country subject to continuous conflicts, and the effect of a political event on its image. A measurement model is examined before and after a specific ...international incident, the Mavi Marmara conflict between Turkey and Israel, in order to understand how this event influences the image that the Turks have of Israel, as well as their intention to visit the place. The results confirm that, when people have previous animosity towards a nation, the image of this country is formed mainly through its affective component and not through its cognitive one. The research concludes that a political conflict between two countries significantly damages the country image through the affective component and boosts the previously held animosity. The incident also increases the negative influence of the affective image on the overall country image and on the intention to visit the place.
•The affective image has a greater weight in forming the overall country image.•Political incidents damage the country image even if the prior image is negative.•Political incidents have a greater effect on the country's affective image.•The affective country image influences visitation intentions.•The perceived level of development of the country affects visitation intentions.
•Roadmap presented for hybrid photovoltaic thermal (PVT) collectors.•A novel indium tin oxide (ITO)-based transparent low-emissivity coating applied directly to a PV cell is presented.•Quantitative ...comparison of evacuated cavities, transparent low-emissivity coatings, and silicon heterojunction photovoltaic cells for improved performance.•Cost requirements for technologies along the roadmap are estimated and compared to today’s costs.
For hybrid photovoltaic-thermal collectors to become competitive with other types of solar energy converters, they must offer high performance at fluid outlet temperatures above 60 °C, as is required for space heating and domestic hot water provision, which together account for nearly 50% of heat demand. A roadmap is presented of the technological advances required to achieve this goal. Strategies for reducing convective, radiative and electrical losses at elevated temperature are discussed, and an experimental characterisation of a novel transparent low-emissivity coating for photovoltaic solar cells is presented. An experimentally-validated simulation formalism is used to project the performance of different combinations of loss-reduction strategies implemented together. Finally, a techno-economic analysis is performed to predict the price points at which the hybrid technologies along the roadmap become competitive with non-hybrid photovoltaic and solar thermal technologies. The most advanced hybrid technology along the roadmap employs an evacuated cavity, a transparent low-emissivity coating, and silicon heterojunction photovoltaic cells.
ABSTRACT
HiPERCAM is a portable, quintuple-beam optical imager that saw first light on the 10.4-m Gran Telescopio Canarias (GTC) in 2018. The instrument uses re-imaging optics and four dichroic ...beamsplitters to record $u_{\rm s}\, g_{\rm s}\, r_{\rm s}\, i_{\rm s}\, z_{\rm s}$ (320–1060 nm) images simultaneously on its five CCD cameras, each of 3.1-arcmin (diagonal) field of view. The detectors in HiPERCAM are frame-transfer devices cooled thermo-electrically to 183 K, thereby allowing both long-exposure, deep imaging of faint targets, as well as high-speed (over 1000 windowed frames per second) imaging of rapidly varying targets. A comparison-star pick-off system in the telescope focal plane increases the effective field of view to 6.7 arcmin for differential photometry. Combining HiPERCAM with the world’s largest optical telescope enables the detection of astronomical sources to gs ∼ 23 in 1 s and gs ∼ 28 in 1 h. In this paper, we describe the scientific motivation behind HiPERCAM, present its design, report on its measured performance, and outline some planned enhancements.
Abstract
The young massive OB association Cygnus OB2, in the Cygnus X complex, is the closest (∼1400 pc) star-forming region to the Sun hosting thousands of young low-mass stars and up to 1000 OB ...stars, among which are some of the most massive stars known in our Galaxy. This region holds great importance for several fields of modern astrophysics, such as the study of the physical properties of massive and young low-mass stars and the feedback provided by massive stars on star and planet formation processes. Cyg OB2 has been recently observed with Chandra/ACIS-I as part of the 1.08 Ms Chandra Cygnus OB2 Legacy Project. This survey detected 7924 X-ray sources in a square degree area centered on Cyg OB2. Since a proper classification and study of the observed X-ray sources also requires the analysis of their optical and infrared counterparts, we combined a large and deep set of optical and infrared catalogs available for this region with our new X-ray catalog. In this paper we describe the matching procedure and present the combined catalog containing 5703 sources. We also briefly discuss the nature of the X-ray sources with optical and infrared counterparts using their position in the color–magnitude and color–color diagrams.
A
bstract
From a gauge SU (2
,
2
|
2) model with broken supersymmetry, we construct an action for SU(2)
×
U (1) Yang-Mills theory coupled to gravity and matter in four dimensions. The connection ...components for AdS boosts and special conformal translations are auxiliary fields and their fixing reduces the theory to two distinct sectors: a vector-like gauge theory with general relativity and a chiral gauge theory where gravity drops out. We discuss some of the main classical features of the model such as the predicted tree level gauge couplings, cosmological constant value, mass-like terms and the Einstein equations.
A
bstract
In this work, we study (anti-)self duality conditions in unconventional conformal supersymmetry. We focus on a theory constructed in a Townsend-MacDowell-Mansouri form for an SU(2
,
2|
N
) ...gauge connection with matter fields in the adjoint representation. We find bosonic solutions that correspond to analytic gravitational instantons with nontrivial torsion. These configurations can be regarded as the torsional generalization of the Taub-NUT/Bolt-AdS and Eguchi-Hanson metric and they are (anti-)self-dual with respect to a generalized dual operator. We explore their global properties and show that they saturate a BPS bound.
.
We explore systematically a new class of two-phase equations of state (EoS) for hybrid stars that is characterized by three main features: 1) stiffening of the nuclear EoS at supersaturation ...densities due to quark exchange effects (Pauli blocking) between hadrons, modelled by an excluded volume correction; 2) stiffening of the quark matter EoS at high densities due to multiquark interactions; and 3) possibility for a strong first-order phase transition with an early onset and large density jump. The third feature results from a Maxwell construction for the possible transition from the nuclear to a quark matter phase and its properties depend on the two parameters used for 1) and 2), respectively. Varying these two parameters, one obtains a class of hybrid EoS that yields solutions of the Tolman-Oppenheimer-Volkoff (TOV) equations for sequences of hadronic and hybrid stars in the mass-radius diagram which cover the full range of patterns according to the Alford-Han-Prakash classification following which a hybrid star branch can be either absent, connected or disconnected with the hadronic one. The latter case often includes a tiny connected branch. The disconnected hybrid star branch, also called “third family”, corresponds to high-mass twin stars characterized by the same gravitational mass but different radii. We perform a Bayesian analysis and demonstrate that the observation of such a pair of high-mass twin stars would have a sufficient discriminating power to favor hybrid EoS with a strong first-order phase transition over alternative EoS.
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