2,372 research outputs found
Astrometric-spectroscopic determination of the absolute masses of the HgMn binary star Phi Herculis
The Mercury-Manganese star Phi Her is a well known spectroscopic binary that
has been the subject of a recent study by Zavala et al. (2006), in which they
resolved the companion using long-baseline interferometry. The total mass of
the binary is now fairly well established, but the combination of the
spectroscopy with the astrometry has not resulted in individual masses
consistent with the spectral types of the components. The motion of the center
of light of Phi Her was clearly detected by the Hipparcos satellite. Here we
make use of the Hipparcos intermediate data (`abscissa residuals') and show
that by combining them in an optimal fashion with the interferometry the
individual masses can be obtained reliably using only astrometry. We re-examine
and then incorporate existing radial-velocity measurements into the orbital
solution, obtaining improved masses of 3.05 +/- 0.24 M_Sun and 1.614 +/- 0.066
M_Sun that are consistent with the theoretical mass-luminosity relation from
recent stellar evolution models. These mass determinations provide important
information for the understanding of the nature of this peculiar class of
stars.Comment: Total of 18 pages including figures and tables, in emulateapj format.
To appear in The Astronomical Journal, June 2007 issu
Buffalo National River Ecosystems - Part II
The priorities were established for the Buffalo National River Ecosystem Studies through meetings and correspondence with Mr. Roland Wauer and other personnel of the Office of Natural Sciences, Southwest Region of the National Park Service. These priorities were set forth in the appendix of contract no. CX 700050443 dated May 21, 1975
Evidence of clonal budding in a radial cluster of Paraconularia crustula (White) (Pennsylvanian: ?Cnidaria)
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73153/1/j.1502-3931.1992.tb01645.x.pd
The laboratory telerobotic manipulator program
New opportunities for the application of telerobotic systems to enhance human intelligence and dexterity in the hazardous environment of space are presented by the NASA Space Station Program. Because of the need for significant increases in extravehicular activity and the potential increase in hazards associated with space programs, emphasis is being heightened on telerobotic systems research and development. The Laboratory Telerobotic Manipulator (LTM) program is performed to develop and demonstrate ground-based telerobotic manipulator system hardware for research and demonstrations aimed at future NASA applications. The LTM incorporates traction drives, modularity, redundant kinematics, and state-of-the-art hierarchical control techniques to form a basis for merging the diverse technological domains of robust, high-dexterity teleoperations and autonomous robotic operation into common hardware to further NASA's research
Pattern selection as a nonlinear eigenvalue problem
A unique pattern selection in the absolutely unstable regime of driven,
nonlinear, open-flow systems is reviewed. It has recently been found in
numerical simulations of propagating vortex structures occuring in
Taylor-Couette and Rayleigh-Benard systems subject to an externally imposed
through-flow. Unlike the stationary patterns in systems without through-flow
the spatiotemporal structures of propagating vortices are independent of
parameter history, initial conditions, and system length. They do, however,
depend on the boundary conditions in addition to the driving rate and the
through-flow rate. Our analysis of the Ginzburg-Landau amplitude equation
elucidates how the pattern selection can be described by a nonlinear eigenvalue
problem with the frequency being the eigenvalue. Approaching the border between
absolute and convective instability the eigenvalue problem becomes effectively
linear and the selection mechanism approaches that of linear front propagation.
PACS: 47.54.+r,47.20.Ky,47.32.-y,47.20.FtComment: 18 pages in Postsript format including 5 figures, to appear in:
Lecture Notes in Physics, "Nonlinear Physics of Complex Sytems -- Current
Status and Future Trends", Eds. J. Parisi, S. C. Mueller, and W. Zimmermann
(Springer, Berlin, 1996
Final Report: Buffalo National River Ecosystems
The objective of this study was to sample the Buffalo River on a seasonal basis for a year, in order to determine whether any potential water quality problems existed
Isomer shift and magnetic moment of the long-lived 1/2 isomer in Zn: signature of shape coexistence near Ni
Collinear laser spectroscopy has been performed on the Zn
isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred
milliseconds half-life was confirmed, and the nuclear spins and moments of the
ground and isomeric states in Zn as well as the isomer shift were
measured. From the observed hyperfine structures, spins and
are firmly assigned to the ground and isomeric states. The magnetic moment
(Zn) = 1.1866(10) , confirms the spin-parity
with a shell-model configuration, in excellent
agreement with the prediction from large scale shell-model theories. The
magnetic moment (Zn) = 1.0180(12) supports a
positive parity for the isomer, with a wave function dominated by a 2h-1p
neutron excitation across the shell gap. The large isomer shift
reveals an increase of the intruder isomer mean square charge radius with
respect to that of the ground state:
= +0.204(6) fm, providing first evidence of shape coexistence.Comment: 5 pages, 4 figures, 1 table, Accepeted by Phys. Rev. Lett. (2016
Projected t-SNE for batch correction
Motivation: Low-dimensional representations of high-dimensional data are routinely employed in biomedical research to visualize, interpret and communicate results from different pipelines. In this article, we propose a novel procedure to directly estimate t-SNE embeddings that are not driven by batch effects. Without correction, interesting structure in the data can be obscured by batch effects. The proposed algorithm can therefore significantly aid visualization of high-dimensional data. Results: The proposed methods are based on linear algebra and constrained optimization, leading to efficient algorithms and fast computation in many high-dimensional settings. Results on artificial single-cell transcription profiling data show that the proposed procedure successfully removes multiple batch effects from t-SNE embeddings, while retaining fundamental information on cell types. When applied to single-cell gene expression data to investigate mouse medulloblastoma, the proposed method successfully removes batches related with mice identifiers and the date of the experiment, while preserving clusters of oligodendrocytes, astrocytes, and endothelial cells and microglia, which are expected to lie in the stroma within or adjacent to the tumours. Contact: [email protected]
Preliminary Reconnaissance Water Quality Survey of the Buffalo National River
In accordance with Contract No. CX 700030105, dated 12 February 1973, the University of Arkansas , Water Resources Resear ch Center is submitting a Preliminary Reconnaissance Water Quality Survey of the Buffalo National River. The Water Resources Research Center of Arkansas has supplied the necessary personnel and facil ities to perform a preliminary reconnaissance survey of the Buffalo National River of Arkansas with special emphasis placed on the establishment of both permanent and temporary benchmarks for water quality sampling. Preliminary water quality samples have been collected to make those chemical, physical, and biological analyses as defined by Mr . Roland H. Wauer and other Park Service personnel on 3 May 1973
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