2,996 research outputs found
Rapid Terrain Generation for GeoVisualization, Simulation, Mission Rehearsal, & Operations
Geospecific 3D terrain representation (aka reality modeling) is revolutionizing geovisualization, simulation, and engineering practices around the world. In tandem with the rapid growth in unmanned aerial systems (UAS) and small satellites, reality modeling advancements now allow geospatial intelligence (GEOINT) practitioners to generate three-dimensional models from a decentralized collection of digital images to meet mission needs in both urban and rural environments. Scalable mesh models deliver enhanced, real-world visualization for engineers, geospatial teams, combatant, and combat support organizations. In this, reality modeling provides a detailed understanding of the physical environment, and models allow installation engineers and GEOINT practitioners to quickly generate updated, high-precision 3D reality meshes to provide real-world digital context for the decision-making process
Videomicroscopy as a tool for investigation of the microcirculation in the newborn
The perinatal period remains a time of significant risk of death or disability. Increasing evidence suggests that this depends on microcirculatory behavior. Sidestream dark-field orthogonal polarized light videomicroscopy (OPS) has emerged as a useful assessment of adult microcirculation but the values derived are not delineated for the newborn. We aimed to define these parameters in well term newborn infants. Demographic details were collected prospectively on 42 healthy term neonates (n = 20 females, n = 22 males). OPS videomicroscopy (Microscan) was used to view ear conch skin microcirculation at 6, 24, and 72 h of age. Stored video was analyzed by a masked observer using proprietary software. There were no significant differences between the sexes for any structural parameters at any time point. There was a significant increase over time in small vessel perfusion in female infants only (P = 0.009). A number of 6- and 72-h measurements were significantly correlated, but differed from the 24-h values. These observations confirm the utility of the ear conch for neonatal microvascular videomicroscopy. They provide a baseline for studies into the use of OPS videomicroscopy in infants. The changes observed are comparable with previous studies of term infants using these and other microvascular techniques. It is recommended that studies for examining the mature neonatal microvascular structure be delayed until 72 h of life, but studies of the physiology of cardiovascular transition should include the 24-h time point after delivery
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Genetic structure and diversity of a rare woodland bat, Myotis bechsteinii: comparison of continental Europe and Britain
The Bechstein’s bat (Myotis bechsteinii) is a rare sedentary bat considered to be highly reliant on the presence of ancient woodland. Understanding the genetic connectivity and population structure of such elusive mammals is important for assessing their conservation status. In this study, we report the genetic diversity and structure of M. bechsteinii across Britain and Europe. Assessments were made using 14 microsatellite markers and a 747 bp region of the mitochondrial cytochrome b gene. Nuclear DNA (microsatellites) showed high levels of genetic diversity and little inbreeding across the species range, though genetic diversity was slightly lower in Britain than in mainland Europe. Bayesian and spatial PCA analysis showed a clear separation between the British and European sites. Within Europe, the Italian population south of the Alps was isolated from the other sites. In Britain, there was genetic structuring between the northern and southern part of the geographical range. Despite there being little genetic divergence in mitochondrial DNA (mtDNA) sequences throughout most of Europe, the mtDNA patterns in Britain confirmed this separation of northern and southern populations. Such genetic structuring within Britain—in the absence of any obvious physical barriers—suggests that other factors such as land-use may limit gene-flow
The Exemplar T8 Subdwarf Companion of Wolf 1130
We have discovered a wide separation (188.5") T8 subdwarf companion to the
sdM1.5+WD binary Wolf 1130. Companionship of WISE J200520.38+542433.9 is
verified through common proper motion over a ~3 year baseline. Wolf 1130 is
located 15.83 +/- 0.96 parsecs from the Sun, placing the brown dwarf at a
projected separation of ~3000 AU. Near-infrared colors and medium resolution
(R~2000-4000) spectroscopy establish the uniqueness of this system as a
high-gravity, low-metallicity benchmark. Although there are a number of
low-metallicity T dwarfs in the literature, WISE J200520.38+542433.9 has the
most extreme inferred metallicity to date with [Fe/H] = -0.64 +/- 0.17 based on
Wolf 1130. Model comparisons to this exemplar late-type subdwarf support it
having an old age, a low metallicity, and a small radius. However, the
spectroscopic peculiarities of WISE J200520.38+542433.9 underscore the
importance of developing the low-metallicity parameter space of the most
current atmospheric models.Comment: Accepted to ApJ on 05 September 2013; 33 pages in preprint format, 8
figures, 3 table
A T8.5 Brown Dwarf Member of the Xi Ursae Majoris System
The Wide-field Infrared Survey Explorer has revealed a T8.5 brown dwarf (WISE
J111838.70+312537.9) that exhibits common proper motion with a
solar-neighborhood (8 pc) quadruple star system - Xi Ursae Majoris. The angular
separation is 8.5 arc-min, and the projected physical separation is about 4000
AU. The sub-solar metallicity and low chromospheric activity of Xi UMa A argue
that the system has an age of at least 2 Gyr. The infrared luminosity and color
of the brown dwarf suggests the mass of this companion ranges between 14 and 38
Jupiter masses for system ages of 2 and 8 Gyr respectively.Comment: AJ in press, 12 pages LaTeX with 6 figures. More astrometric data and
a laser guide star adaptive optics image adde
The AllWISE Motion Survey, Part 2
We use the AllWISE Data Release to continue our search for WISE-detected
motions. In this paper, we publish another 27,846 motion objects, bringing the
total number to 48,000 when objects found during our original AllWISE motion
survey are included. We use this list, along with the lists of confirmed
WISE-based motion objects from the recent papers by Luhman and by Schneider et
al. and candidate motion objects from the recent paper by Gagne et al. to
search for widely separated, common-proper-motion systems. We identify 1,039
such candidate systems. All 48,000 objects are further analyzed using
color-color and color-mag plots to provide possible characterizations prior to
spectroscopic follow-up. We present spectra of 172 of these, supplemented with
new spectra of 23 comparison objects from the literature, and provide
classifications and physical interpretations of interesting sources. Highlights
include: (1) the identification of three G/K dwarfs that can be used as
standard candles to study clumpiness and grain size in nearby molecular clouds
because these objects are currently moving behind the clouds, (2) the
confirmation/discovery of several M, L, and T dwarfs and one white dwarf whose
spectrophotometric distance estimates place them 5-20 pc from the Sun, (3) the
suggestion that the Na 'D' line be used as a diagnostic tool for interpreting
and classifying metal-poor late-M and L dwarfs, (4) the recognition of a triple
system including a carbon dwarf and late-M subdwarf, for which model fits of
the late-M subdwarf (giving [Fe/H] ~ -1.0) provide a measured metallicity for
the carbon star, and (5) a possible 24-pc-distant K5 dwarf + peculiar red L5
system with an apparent physical separation of 0.1 pc.Comment: 62 pages with 80 figures, accepted for publication in The
Astrophysical Journal Supplement Series, 23 Mar 2016; second version fixes a
few small typos and corrects the footnotes for Table
A Study of the Diverse T Dwarf Population Revealed by WISE
We report the discovery of 87 new T dwarfs uncovered with the Wide-field
Infrared Survey Explorer (WISE) and three brown dwarfs with extremely red
near-infrared colors that exhibit characteristics of both L and T dwarfs. Two
of the new T dwarfs are likely binaries with L7+/-1 primaries and mid-type T
secondaries. In addition, our follow-up program has confirmed 10 previously
identified T dwarfs and four photometrically-selected L and T dwarf candidates
in the literature. This sample, along with the previous WISE discoveries,
triples the number of known brown dwarfs with spectral types later than T5.
Using the WISE All-Sky Source Catalog we present updated color-color and
color-type diagrams for all the WISE-discovered T and Y dwarfs. Near-infrared
spectra of the new discoveries are presented, along with spectral
classifications. To accommodate later T dwarfs we have modified the integrated
flux method of determining spectral indices to instead use the median flux.
Furthermore, a newly defined J-narrow index differentiates the early-type Y
dwarfs from late-type T dwarfs based on the J-band continuum slope. The K/J
indices for this expanded sample show that 32% of late-type T dwarfs have
suppressed K-band flux and are blue relative to the spectral standards, while
only 11% are redder than the standards. Comparison of the Y/J and K/J index to
models suggests diverse atmospheric conditions and supports the possible
re-emergence of clouds after the L/T transition. We also discuss peculiar brown
dwarfs and candidates that were found not to be substellar, including two Young
Stellar Objects and two Active Galactic Nuclei. The coolest WISE-discovered
brown dwarfs are the closest of their type and will remain the only sample of
their kind for many years to come.Comment: Accepted to ApJS on 15 January 2013; 99 pages in preprint format, 30
figures, 12 table
The First ALLWISE Proper Motion Discovery: WISEA J070720.50+170532.7
While quality checking a new motion-aware co-addition of all 12.5 months of Wide-field Infrared Survey Explorer (WISE) data, we found that the source WISE J070720.48+170533.0 moved 0".9 in six months. Backtracking this motion allowed us to identify this source as 2MASS J07071961+1705464, with several entries in the USNO B catalog. An astrometric fit to these archival data gives a proper motion of μ = 1793 ± 2 mas yr^(–1) and a parallax of ω = 35 ± 42 mas. Photometry from WISE, 2MASS, and the POSS can be fit reasonably well by a blackbody with T = 3658 K and an angular radius of 4.36 × 10^(–11) radians. No clear evidence of H_2 collision-induced absorption is seen in the near-infrared. An optical spectrum shows broad deep CaH bands at 638 and 690 nm, broad deep Na D at 598.2 nm, and weak or absent TiO, indicating that this source is an ultra-subdwarf M star with a radial velocity v_(rad) ≈ –21 ± 18 km s^(–1) relative to the Sun. Given its apparent magnitude, the distance is about 39 ± 9 pc and the tangential velocity is probably ≈330 km s^(–1), but a more precise parallax is needed to be certain
Y Dwarf Trigonometric Parallaxes from the Spitzer Space Telescope
Y dwarfs provide a unique opportunity to study free-floating objects with masses <30 M_(Jup) and atmospheric temperatures approaching those of known Jupiter-like exoplanets. Obtaining distances to these objects is an essential step toward characterizing their absolute physical properties. Using Spitzer's Infrared Array Camera (IRAC) [4.5] images taken over baselines of ~2–7 years, we measure astrometric distances for 22 late-T and early Y dwarfs, including updated parallaxes for 18 objects and new parallax measurements for 4 objects. These parallaxes will make it possible to explore the physical parameter space occupied by the coldest brown dwarfs. We also present the discovery of six new late-T dwarfs, updated spectra of two T dwarfs, and the reclassification of a new Y dwarf, WISE J033605.04−014351.0, based on Keck/NIRSPEC J-band spectroscopy. Assuming that effective temperatures are inversely proportional to absolute magnitude, we examine trends in the evolution of the spectral energy distributions of brown dwarfs with decreasing effective temperature. Surprisingly, the Y dwarf class encompasses a large range in absolute magnitude in the near- to mid-infrared photometric bandpasses, demonstrating a larger range of effective temperatures than previously assumed. This sample will be ideal for obtaining mid-infrared spectra with the James Webb Space Telescope because their known distances will make it easier to measure absolute physical properties
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