2,317 research outputs found
Distance to U Pegasi by the DDE Algorithm
A distance is found for the W UMa type binary U Pegasi, with a newly modified
version of the Wilson-Devinney program (W-D) that makes use of the direct
distance estimation (DDE) algorithm. The reported distance of d = 123.6pc is an
average based on solutions for B and V data and a primary star temperature of
5800K. Standardized light curves (not differential), radial velocities, and a
spectroscopic primary star temperature are input to the pro- gram. Differential
corrections were performed for each light curve band along with the velocities
for two primary temperatures that span 100K. Log10d is a model parameter like
many others that are adjustable in W-D. The eclipsing binary distance agrees
with the Hipparcos parallax distance and is more precise.Comment: 2 pages, 1 table, International Conference: Binaries - Key to
Comprehension of the Universe, Brno, Czech Republic June 8-12, 200
The V471 Tauri System: A Multi-datatype Probe
V471 Tauri, a white dwarf--red dwarf eclipsing binary in the Hyades, is well
known for stimulating development of common envelope theory, whereby novae and
other cataclysmic variables form from much wider binaries by catastrophic orbit
shrinkage. Our evaluation of a recent imaging search that reported negative
results for a much postulated third body shows that the object could have
escaped detection or may have actually been seen. The balance of evidence
continues to favor a brown dwarf companion about 12 AU from the eclipsing
binary. A recently developed algorithm finds unified solutions from three
datatypes. New radial velocities (RVs) of the red dwarf and BV RCIC light
curves are solved simultaneously along with white dwarf and red dwarf RVs from
the literature, uvby data, the MOST mission light curve, and 40 years of
eclipse timings. Precision-based weighting is the key to proper information
balance among the various datasets. Timewise variation of modeled starspots
allows unified solution of multiple data eras. Light curve amplitudes strongly
suggest decreasing spottedness from 1976 to about 1980, followed by
approximately constant spot coverage from 1981 to 2005. An explanation is
proposed for lack of noticeable variation in 1981 light curves, in terms of
competition between spot and tidal variations. Photometric spectroscopic
distance is estimated. The red dwarf mass comes out larger than normal for a
K2V star, and even larger than adopted in several structure and evolution
papers. An identified cause for this result is that much improved red dwarf RVs
curves now exist
Your Place in Space: Classroom Experiment on Spatial Location Theory
The authors detail an urban economics experiment that is easily run in the classroom. The experiment has a flexible design that allows the instructor to explore how congestion, zoning, public transportation, and taxation levels determine the bid-rent function. Heterogeneous agents in the experiment compete for land use utilizing a simple auction mechanism. Using the data that is collected, a bid-rent function is derived, and the experimental treatment is altered over the course of three sessions to uncover core concepts in urban economics. Moreover, this provides a tangible experience that can be used to help undergraduates relate to urban issues such as the steep rent gradient found around many larger colleges and universities.
A BVRcIc Survey of W Ursae Majoris Binaries
We report on a BVRcIc survey of field W Ursae Majoris binary stars and
present accurate colors for 606 systems that have been observed on at least
three photometric nights from a robotic observatory in southern Arizona.
Comparison with earlier photometry for a subset of the systems shows good
agreement. We investigate two independent methods of determining the
interstellar reddening, although both have limitations that can render them
less effective than desired. A subset of 101 systems shows good agreement
between the two reddening methods.Comment: 10 pages, 6 figures, accepted for publication in A
Your Place in Space: Classroom Experiment on Spatial Location Theory
The authors detail an urban economics experiment that is easily run in the classroom. The experiment has a flexible design that allows the instructor to explore how congestion, zoning, public transportation, and taxation levels determine the bid-rent function. Heterogeneous agents in the experiment compete for land use utilizing a simple auction mechanism. Using the data that is collected, a bid-rent function is derived, and the experimental treatment is altered over the course of three sessions to uncover core concepts in urban economics. Moreover, this provides a tangible experience that can be used to help undergraduates relate to urban issues such as the steep rent gradient found around many larger colleges and universities
Longitudinal evaluation of myocardial function in preterm infants with respiratory distress syndrome
Aim
Preterm births and respiratory distress syndrome (RDS) are associated with pulmonary vascular disease and altered myocardial function. We serially assessed up to 1 year of age the effects of RDS on global and regional myocardial function of preterm infants, compared to preterm and term controls using conventional echocardiography parameters, tissue Doppler velocities and deformation analysis.
Methods and results
A total of 120 infants (30 preterm [PT] with RDS, 30 PT controls without RDS, and 60 term controls) underwent conventional and tissue Doppler echocardiography within 72 hours of birth, at corrected term age for the preterm infants, at 1 month corrected, and at 1 year corrected age. At birth, compared to preterm and term controls, the PT‐RDS group had decreased right ventricular (RV) long‐axis function, systolic velocity, peak systolic strain, shorter pulmonary arterial acceleration time (PAAT), and lower ratio of PAAT to RV ejection time (PAAT:RVET). Preterm infants had left ventricular (LV) diastolic dysfunction at birth (lower early diastolic myocardial velocity, mitral E velocity, and mitral E:A ratio), and reduced long‐axis systolic velocities and shortening. Differences between groups disappeared by 1 month corrected age, except PAAT:RVET which remained lower in the PT‐RDS group. At 1 year, RV function was normal in PT‐RDS apart from systolic strain rate, and LV function was normal apart from lower stroke volume and shortening, relative to body weight.
Conclusion
PT‐RDS had lower left and right ventricular systolic and diastolic function at birth which improved over time, suggesting postnatal maturation of cardiac function and resolution of lung disease
The kagom\'e metals RbTiBi and CsTiBi
The kagom\'e metals RbTiBi and CsTiBi were synthesized both
as polycrystalline powders by heating the elements an argon atmosphere and as
single crystals grown using a self-flux method. The compounds crystallize in
the hexagonal crystal system isotypically to KVSb (P6/mmm, Z = 1,
CsTi3Bi5: a = 5.7873(1) {\AA}, c = 9.2062(1) {\AA}; RbTi3Bi5: a = 5.773(1)
{\AA}, c = 9.065(1) {\AA}). Titanium atoms form a kagom\'e net with bismuth
atoms in the hexagons as well as above and below the triangles. The alkali
metal atoms are coordinated by 12 bismuth atoms and form AlB-like slabs
between the kagom\'e layers. Magnetic susceptibility measurements with
CsTiBi and RbTiBi single crystals reveal Pauli-paramagnetism
and traces of superconductivity caused by CsBi/RbBi impurities.
Magnetotransport measurements reveal conventional Fermi liquid behavior and
quantum oscillations indicative of a single dominant orbit at low temperature.
DFT calculations show the characteristic metallic kagom\'e band structure
similar to that of CsVSb with reduced band filling. A symmetry analysis
of the band structure does not reveal an obvious and unique signature of a
nontrivial topology.Comment: 20 pages, 5 Figures, submitte
Mental Well-being during Stages of COVID-19 Lockdown among pregnant women and new mothers
Acknowledgments The authors would like to thank the funders for their financial support and research assistant Sinead Shahrzad for data management. Funding This work was supported by TRYGfonden [grant number 125227] and the quality and continuing education committee for general practice in the Capital Region [grant number 19035774].Peer reviewedPublisher PD
Multislice computed tomography/contrast-enhanced ultrasound image fusion as a tool for evaluating unclear renal cysts
Ultrasonography is a generally accepted imaging technique for diagnosing and monitoring cystic renal lesions. The widely used Bosniak classification (I-IV) categorizes renal cystic lesions into five distinctive groups according to ultrasonography and computed tomography (CT) image criteria. For solid renal lesions, determination of vascularity is discriminatory for malignancy in most instances. In indeterminate cases, contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging/CT-ultrasound image fusion are able to detect and characterize difficult pathologies, with superior performance to either technique alone. In contrast to multislice CT (MS-CT), ultrasound image fusion is a real-time imaging technique that can be used in combination with other cross-sectional imaging modalities. This technical note describes state-of-the-art image fusion of CEUS and MS-CT to detect and characterize unclear renal pathologies
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