4,234 research outputs found
Liquid-Vapor Equilibrium of Multicomponent Cryogenic Systems
Liquid-vapor and solid-vapor equilibria at low to moderate pressures and low temperatures are important in many solar system environments, including the surface and clouds of Titan, the clouds of Uranus and Neptune, and the surfaces of Mars and Triton. The familiar cases of ideal behavior are limiting cases of a general thermodynamic representation for the vapor pressure of each component in a homogeneous multicomponent system. The fundamental connections of laboratory measurements to thermodynamic models are through the Gibbs-Duhem relation and the Gibbs-Helmholtz relation. Using laboratory measurements of the total pressure, temperature, and compositions of the liquid and vapor phases at equilibrium, the values of these parameters can be determined. The resulting model for vapor-liquid equilibrium can then conveniently and accurately be used to calculate pressures, compositions, condensation altitudes, and their dependencies on changing climatic conditions. A specific system being investigated is CH4-C2H6-N2, at conditions relevant to Titan's surface and atmosphere. Discussed are: the modeling of existing data on CH4-N2, with applications to the composition of Titan's condensate clouds; some new measurements on the CH4-C2H6 binary, using a high-precision static/volumetric system, and on the C2H6-N2 binary, using the volumetric system and a sensitive cryogenic flow calorimeter; and describe a new cryogenic phase-equilibrium vessel with which we are beginning a detailed, systematic study of the three constituent binaries and the ternary CH4-C2H6-N2 system at temperatures ranging from 80 to 105 K and pressures from 0.1 to 7 bar
Inoculating an Infodemic: An Ecological Approach to Understanding Engagement With COVID-19 Online Information
As the global COVID-19 pandemic has been concurrently labelled an “infodemic,” researchers have sought to improve how the general public engages with information that is relevant, timely, and accurate. In this study, we provide an overview of the reasons why people engage and disengage with COVID-19 information. We use context-rich semi-structured interviews which invited participants to discuss online COVID-19-related content they encountered. This qualitative approach allows us to uncover subtle but important details of influences that drive online engagement. Participants both engaged and disengaged with content for individual and social reasons, with seven themes emerging connected to their engagement including actions in response to information, reasoning for engagement, content, motivating concerns, frequency of engagement with information, site of exposure, and given reason for not engaging. Many of these themes intersected and informed each other. Our findings suggest that researchers and public health communicators should approach engagement as an ecology of intersecting influences, both human and algorithmic, which change over time. This information could be potentially helpful to public health communicators who are trying to engage the public with the best information to keep them safe during the pandemic
The health belief model: How public health can address the misinformation crisis beyond COVID-19
Objectives:
This paper proposes an intervention into health misinformation that relies upon the health belief model as a means to bridge the risks associated with health misinformation and the impact on individual health, beyond the current recommendations for fact checking and information literacy.
Study design:
This is a short theoretical paper.
Methods:
N/A.
Results:
N/A.
Conclusions:
Misinformation researchers and public health practitioners and communicators can benefit using the infrastructures afforded by public health offices to mobilize the health belief model as a site for misinformation education
Variable Stars in the Globular Cluster M5. Application of the Image Subtraction Method
We present -band light curves of 61 variables from the core of the
globular cluster M5 obtained using a newly developed image subtraction method
(ISM). Four of these variables were previously unknown. Only 26 variables were
found in the same field using photometry obtained with DoPHOT software. Fourier
parameters of the ISM light curves have relative errors up to 20 times smaller
than parameters measured from DoPHOT photometry. We conclude that the new
method is very promising for searching for variable stars in the cores of the
globular clusters and gives very accurate relative photometry with quality
comparable to photometry obtained by HST. We also show that the variable V104
is not an eclipsing star as has been suggested, but is an RRc star showing
non-radial pulsations.Comment: submitted to MNRAS, 9 pages, 4 figure
Mass distributions of stars and cores in young groups and clusters
We investigate the relation of the stellar initial mass function (IMF) and
the dense core mass function (CMF), using stellar masses and positions in 14
well-studied young groups. Initial column density maps are computed by
replacing each star with a model initial core having the same star formation
efficiency (SFE). For each group the SFE, core model, and observational
resolution are varied to produce a realistic range of initial maps. A
clumpfinding algorithm parses each initial map into derived cores, derived core
masses, and a derived CMF. The main result is that projected blending of
initial cores causes derived cores to be too few and too massive. The number of
derived cores is fewer than the number of initial cores by a mean factor 1.4 in
sparse groups and 5 in crowded groups. The mass at the peak of the derived CMF
exceeds the mass at the peak of the initial CMF by a mean factor 1.0 in sparse
groups and 12.1 in crowded groups. These results imply that in crowded young
groups and clusters, the mass distribution of observed cores may not reliably
predict the mass distribution of protostars which will form in those cores.Comment: 48 pages, 17 figures, accepted for publication in Astrophysical
Journa
Variation in the Diagnosis and Management of Appendicitis at Canadian Pediatric Hospitals
Objectives The objective was to characterize the variations in practice in the diagnosis and management of children admitted to hospitals from Canadian pediatric emergency departments (EDs) with suspected appendicitis, specifically the timing of surgical intervention, ED investigations, and management strategies. Methods Twelve sites participated in this retrospective health record review. Children aged 3 to 17 years admitted to the hospital with suspected appendicitis were eligible. Site-specific demographics, investigations, and interventions performed were recorded and compared. Factors associated with after-hours surgery were determined using generalized estimating equations logistic regression. Results Of the 619 children meeting eligibility criteria, surgical intervention was performed in 547 (88%). After-hours surgery occurred in 76 of the 547 children, with significant variation across sites (13.9%, 95% confidence interval = 7.1% to 21.6%, p \u3c 0.001). The overall perforation rate was 17.4% (95 of 547), and the negative appendectomy rate was 6.8% (37 of 547), varying across sites (p = 0.004 and p = 0.036, respectively). Use of inflammatory markers (p \u3c 0.001), blood cultures (p \u3c 0.001), ultrasound (p = 0.001), and computed tomography (p = 0.001) also varied by site. ED administration of narcotic analgesia and antibiotics varied across sites (p \u3c 0.001 and p = 0.001, respectively), as did the type of surgical approach (p \u3c 0.001). After-hours triage had a significant inverse association with after-hours surgery (p = 0.014). Conclusions Across Canadian pediatric EDs, there exists significant variation in the diagnosis and management of children with suspected appendicitis. These results indicate that the best diagnostic and management strategies remain unclear and support the need for future prospective, multicenter studies to identify strategies associated with optimal patient outcomes
Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2 and SrNi2P2
We have performed low-temperature specific heat and thermal conductivity
measurements on the Ni-pnictide superconductors BaNiAs
(=0.7 K and SrNiP (=1.4 K). The temperature
dependences and of the two compounds are similar to the
results of a number of s-wave superconductors. Furthermore, the concave field
responses of the residual for BaNiAs rules out the presence of
nodes on the Fermi surfaces. We postulate that fully gapped superconductivity
could be universal for Ni-pnictide superconductors. Specific heat data on
BaLaNiAs shows a mild suppression of and
relative to BaNiAs.Comment: 5 pages, 3 figures, to be published in J. Phys.: Conf. Se
Investigation of the Neutron Form Factors by Inclusive Quasi-Elastic Scattering of Polarized Electrons off Polarized He: A Theoretical Overview
The theory of quasi-elastic inclusive scattering of polarized leptons off
polarized He is critically reviewed and the origin of different expressions
for the polarized nuclear response function appearing in the literature is
explained. The sensitivity of the longitudinal asymmetry upon the neutron form
factors is thoroughly investigated and the role played by the polarization
angle for minimizing the proton contribution is illustrated.Comment: Phys. Rev C in press; 9 figs. (available upon request
Spectrophotometric Distances to Galactic H\,{\sc{ii}} Regions
We present a near infrared study of the stellar content of 35 H\,{\sc{ii}}
regions in the Galactic plane. In this work, we have used the near infrared
domain , and band color images to visually inspect the
sample. Also, color-color and color-magnitude diagrams were used to indicate
ionizing star candidates, as well as, the presence of young stellar objects
such as classical TTauri Stars (CTTS) and massive young stellar objects
(MYSOs). We have obtained {\it Spitzer} IRAC images for each region to help
further characterize them. {\it Spitzer} and near infrared morphology to place
each cluster in an evolutionary phase of development. {\it Spitzer} photometry
was also used to classify the MYSOs. Comparison of the main sequence in
color-magnitude diagrams to each observed cluster was used to infer whether or
not the cluster kinematic distance is consistent with brightnesses of the
stellar sources. We find qualitative agreement for a dozen of the regions, but
about half the regions have near infrared photometry that suggests they may be
closer than the kinematic distance. A significant fraction of these already
have spectrophotometric parallaxes which support smaller distances. These
discrepancies between kinematic and spectrophotometric distances are not due to
the spectrophotometric methodologies, since independent non-kinematic
measurements are in agreement with the spectrophotometric results. For
instance, trigonometric parallaxes of star-forming regions were collected from
the literature and show the same effect of smaller distances when compared to
the kinematic results. In our sample of H\,{\sc{ii}} regions, most of the
clusters are evident in the near infrared images. Finally, it is possible to
distinguish among qualitative evolutionary stages for these objects.Comment: 59 pages, 146 figures and 4 tables. MNRAS accepte
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