1,331 research outputs found
The USNO-B Catalog
USNO-B is an all-sky catalog that presents positions, proper motions,
magnitudes in various optical passbands, and star/galaxy estimators for
1,042,618,261 objects derived from 3,643,201,733 separate observations. The
data were obtained from scans of 7,435 Schmidt plates taken for the various sky
surveys during the last 50 years. USNO-B1.0 is believed to provide all-sky
coverage, completeness down to V = 21, 0.2 arcsecond astrometric accuracy at
J2000, 0.3 magnitude photometric accuracy in up to five colors, and 85%
accuracy for distinguishing stars from non-stellar objects. A brief discussion
of various issues is given here, but the actual data are available from
http://www.nofs.navy.mil and other sites.Comment: Accepted by Astronomical Journa
Trigonometric Parallaxes of Central Stars of Planetary Nebulae
Trigonometric parallaxes of 16 nearby planetary nebulae are presented,
including reduced errors for seven objects with previous initial results and
results for six new objects. The median error in the parallax is 0.42 mas, and
twelve nebulae have parallax errors less than 20 percent. The parallax for
PHL932 is found here to be smaller than was measured by Hipparcos, and this
peculiar object is discussed. Comparisons are made with other distance
estimates. The distances determined from these parallaxes tend to be
intermediate between some short distance estimates and other long estimates;
they are somewhat smaller than estimated from spectra of the central stars.
Proper motions and tangential velocities are presented. No astrometric
perturbations from unresolved close companions are detected.Comment: 24 pages, includes 4 figures. Accepted for A
Strong Water Absorption in the Dayside Emission Spectrum of the Planet HD 189733b
Recent observations of the extrasolar planet HD 189733b did not reveal the
presence of water in the emission spectrum of the planet. Yet models of such
'Hot Jupiter' planets predict an abundance of atmospheric water vapour.
Validating and constraining these models is crucial for understanding the
physics and chemistry of planetary atmospheres in extreme environments.
Indications of the presence of water in the atmosphere of HD 189733b have
recently been found in transmission spectra, where the planet's atmosphere
selectively absorbs the light of the parent star, and in broadband photometry.
Here we report on the detection of strong water absorption in a high
signal-to-noise, mid-infrared emission spectrum of the planet itself. We find
both a strong downturn in the flux ratio below 10 microns and discrete spectral
features that are characteristic of strong absorption by water vapour. The
differences between these and previous observations are significant and admit
the possibility that predicted planetary-scale dynamical weather structures
might alter the emission spectrum over time. Models that match the observed
spectrum and the broadband photometry suggest that heat distribution from the
dayside to the night side is weak. Reconciling this with the high night side
temperature will require a better understanding of atmospheric circulation or
possible additional energy sources.Comment: 11 pages, 1 figure, published in Natur
Extraversion and the Rewarding Effects of Alcohol in a Social Context
The personality trait of extraversion has been linked to problematic drinking patterns. Researchers have long hypothesized that such associations are attributable to increased alcohol-reward sensitivity among extraverted individuals, and surveys suggest that individuals high in extraversion gain greater mood enhancement from alcohol than those low in extraversion. Surprisingly, however, alcohol administration studies have not found individuals high in extraversion to experience enhanced mood following alcohol consumption. Of note, prior studies have examined extraverted participants-individuals who selfidentify as being highly social-consuming alcohol in isolation. In the present research, we used a group drinking paradigm to examine whether individuals high in extraversion gained greater reward from alcohol than did those low in extraversion and, further, whether a particular social mechanism (partners' Duchenne smiling) might underlie alcohol reward sensitivity among extraverted individuals. Social drinkers (n Ď 720) consumed a moderate dose of alcohol, placebo, or control beverage in groups of 3 over the course of 36 min. This social interaction was video-recorded, and Duchenne smiling was coded using the Facial Action Coding System. Results indicated that participants high in extraversion reported significantly more mood enhancement from alcohol than did those low in extraversion. Further, mediated moderation analyses focusing on Duchenne smiling of group members indicated that social processes fully and uniquely accounted for alcohol reward-sensitivity among individuals high in extraversion. Results provide initial experimental evidence that individuals high in extraversion experience increased mood-enhancement from alcohol and further highlight the importance of considering social processes in the etiology of alcohol use disorder
Hairy Black Holes in String Theory
Solutions of bosonic string theory are constructed which correspond to
four-dimensional black holes with axionic quantum hair. The basic building
blocks are the renormalization group flows of the CP1 model with a theta term
and the SU(1,1)/U(1) WZW coset conformal field theory. However the solutions
are also found to have negative energy excitations, and are accordingly
expected to decay to the vacuum.Comment: 14 pages (References added
Application Inflation for Internal Medicine Applicants in the Match: Drivers, Consequences, and Potential Solutions
Electrocorticogram as the Basis for a Direct Brain Interface: Opportunities for Improved Detection Accuracy
A direct brain interface (DBI) based on the detection of event-related potentials (ERPs) in human electrocorticogram (ECoG) is under development. Accurate detection has been demonstrated with this approach (near 100% on a few channels) using a single-channel cross-correlation template matching (CCTM) method. Several opportunities for improved detection accuracy have been identified. Detection using a multiple-channel CCTM method and a variety of detection methods that take advantage of the simultaneous occurrence of ERPs and event-related desynchronization/synchronization (ERD/ERS) have been demonstrated to offer potential for improved detection accuracy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85993/1/Fessler183.pd
The Use of Microgravity Simulators for Space Research
The spaceflight environment is known to influence biological processes ranging from stimulation of cellular metabolism to possible impacts on cellular damage repair, suppression of immune functions, and bone loss in astronauts. Microgravity is one of the most significant stress factors experienced by living organisms during spaceflight, and therefore, understanding cellular responses to altered gravity at the physiological and molecular level is critical for expanding our knowledge of life in space. Since opportunities to conduct experiments in space are scarce, various microgravity simulators and analogues have been widely used in space biology ground studies. Even though simulated microgravity conditions have produced some, but not all of the biological effects observed in the true microgravity environment, they provide test beds that are effective, affordable, and readily available to facilitate microgravity research. A Micro-g Simulator Center is being developed at Kennedy Space Center (KSC) to offer a variety of microgravity simulators and platforms for Space Biology investigators. Assistance will be provided by both KSC and external experts in molecular biology, microgravity simulation, and engineering. Comparisons between the physical differences in microgravity simulators, examples of experiments using the simulators, and scientific questions regarding the use of microgravity simulators will be discussed
Hardware Validation Test of the Advanced Plant Habitat
An automated plant growth facility for conducting plant research supporting space biology and food production project on the International Space Station (ISS)
- …