996 research outputs found
Iatrogenic Claudication from a Vascular Closure Device after Cardiac Catheterization
We report a case of iatrogenic claudication as a result of a misplaced percutaneous arterial closure device (PACD) used to obtain hemostasis after cardiac catheterization. The patient presented one week after his procedure with complaints suggestive of right lower extremity claudication. Computed tomographic angiography demonstrated a near total occlusion of the right common femoral artery from a PACD implemented during the cardiac catheterization. The use of PACD’s to obtain rapid hemostasis is estimated to occur in half of all cardiac catheterizations. Ischemic complications as a result of these devices must be considered when evaluating post procedural patients with extremity complaints
The five-minute oscillations: What's left to be done
Current observational methods for studying these oscillations at large horizontal wavenumbers are discussed in detail and several two dimensional power spectra obtained with a CID camera on the main spectrograph of the McMath telescope at Kitt Peak National Observatory are described. The best-resolved observations of the p-mode obtained at chromospheric elevations are also presented. Recent progress in studies of the p-modes at low wavenumbers with full-disk velocity detection schemes is summarized. These full-disk observations of radial and low-degree non-radial modes were shown to place severe constraints on the theoretical calculation of solar interior structure. Progress in making fully-consistent solar models which fit both the high- and low-wave number observations is described. Finally, the observational and theoretical improvements that are necessary for further progress in solar seismology are summarized
Atmospheric Models for Mars Aerocapture
level Mars atmospheric model. Applications include systems design, performance analysis, and operations planning for aerobraking, entry descent and landing, and aerocapture. Typical Mars aerocapture periapsis altitudes (for systems with rigid- aeroshell heat shields) are about 50 km. This altitude is above the 0-40 km height range covered by Mars Global Surveyor Thermal Emission Spectrometer (TES) nadir observations. Recently, TES limb sounding data have been made available, spanning more than two Mars years (more than 200,000 data profiles) with altitude coverage up to about 60 km, well within the height range of interest for aerocapture. Results are presented comparing Mars-GRAM atmospheric density with densities from TES nadir and limb sounding observations. A new Mars-GRAM feature is described which allows individual TES nadir or limb profiles to be extracted from the large TES databases, and to be used as an optional replacement for standard Mars-GRAM background (climatology) conditions. For Monte-Carlo applications such as aerocapture guidance and control studies, Mars-GRAM perturbations are available using these TES profile background conditions
Helioseismic detection of deep meridional flow
Steady meridional flow makes no first-order perturbation to the frequencies
of helioseismic normal modes. It does, however, Doppler shift the local
wavenumber, thereby distorting the eigenfunctions. For high-degree modes, whose
peaks in a power spectrum are blended into continuous ridges, the effect of the
distortion is to shift the locations of those ridges. From this blended
superposition of modes, one can isolate oppositely directed wave components
with the same local horizontal wavenumber and measure a frequency difference
which can be safely used to infer the subsurface background flow. But such a
procedure fails for the components of the more-deeply-penetrating low-degree
modes that are not blended into ridges. Instead, one must analyze the spatial
distortions explicitly. With a simple toy model, we illustrate one method by
which that might be accomplished by measuring the spatial variation of the
oscillation phase. We estimate that by this procedure it might be possible to
infer meridional flow deep in the solar convection zone.Comment: 23 pages, 9 color figures, submitted to the Astrophysical Journa
Mars Aerocapture and Validation of Mars-GRAM with TES Data
Mars Global Reference Atmospheric Model (Mars-GRAM) is a widely-used engineering- level Mars atmospheric model. Applications include systems design, performance analysis, and operations planning for aerobraking, entry descent and landing, and aerocapture. Typical Mars aerocapture periapsis altitudes (for systems with rigid-aeroshell heat shields) are about 50 km. This altitude is above the 0-40 km height range covered by Mars Global Surveyor Thermal Emission Spectrometer (TES) nadir observations. Recently, TES limb sounding data have been made available, spanning more than two Mars years (more than 200,000 data profiles) with altitude coverage up to about 60 km, well within the height range of interest for aerocapture. Results are presented comparing Mars-GRAM atmospheric density with densities from TES nadir and limb sounding observations. A new Mars-GRAM feature is described which allows individual TES nadir or limb profiles to be extracted from the large TES databases, and to be used as an optional replacement for standard Mars-GRAM background (climatology) conditions. For Monte-Carlo applications such as aerocapture guidance and control studies, Mars-GRAM perturbations are available using these TES profile background conditions
GLOBAL REFERENCE ATMOSPHERIC MODELS FOR AEROASSIST APPLICATIONS
Aeroassist is a broad category of advanced transportation technology encompassing aerocapture, aerobraking, aeroentry, precision landing, hazard detection and avoidance, and aerogravity assist. The eight destinations in the Solar System with sufficient atmosphere to enable aeroassist technology are Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Saturn's moon Titan. Engineering-level atmospheric models for five of these targets - Earth, Mars, Titan, Neptune, and Venus - have been developed at NASA's Marshall Space Flight Center. These models are useful as tools in mission planning and systems analysis studies associated with aeroassist applications. The series of models is collectively named the Global Reference Atmospheric Model or GRAM series. An important capability of all the models in the GRAM series is their ability to simulate quasi-random perturbations for Monte Carlo analysis in developing guidance, navigation and control algorithms, for aerothermal design, and for other applications sensitive to atmospheric variability. Recent example applications are discussed
Oscillations in β Ursae Minoris
Aims. From observations of the K4III star β UMi we attempt to determine whether oscillations or any other form of variability is present.
Methods. A high-quality photometric time series of ≈1000 days in length obtained from the SMEI instrument on the Coriolis satellite is analysed. Various statistical tests were performed to determine the significance of features seen in the power density spectrum of the light curve.
Results. Two oscillations with frequencies 2.44 and 2.92 μHz have been identified. We interpret these oscillations as consecutive overtones of an acoustic spectrum, implying a large frequency spacing of 0.48 μHz. Using derived asteroseismic parameters in combination with known astrophysical parameters, we estimate the mass of β UMi to be 1.3 ± 0.3 M. Peaks of the oscillations in the
power density spectrum show width, implying that modes are stochastically excited and damped by convection. The mode lifetime is estimated at 18 ± 9 days
Complex Transitions Between C3 and C4 Photosynthesis During the Evolution of Paniceae: A Phylogenetic Case Study Emphasizing the Position of Steinchisma Hians (Poaceae), A C3-C4 Intermediate
A two-tiered, nested molecular phylogenetic study of panicoid grasses to explore character state transitions
between the C3 and C4 adaptive syndromes is presented. A broad survey of 92 panicoid species was sampled
for the grass-specific insert sequence in the chloroplast RNA polymerase locus (rpoC2), combining published
and unpublished sequences. This portion of the study also included an intensive phylogenetic investigation of
one clade of seven species that included Steinchisma hians, which is notable for exhibiting intermediacy between
the C3 and C4 photosynthetic types. Both rpoC2 data and previously published sequences of the F subunit of
an NADH-dependent dehydrogenase were analyzed together for this small group. A rigorous phylogenetic
investigation of S. hians and 13 other species of Panicoideae included in the broad survey was then performed
with sequences of both rpoC2 and the externally transcribed spacer region of the nuclear ribosomal repeat.
These 14 species were selected to maximize representation among photosynthetic subtypes. Combined analysis
resolved single origins of two photosynthetic subtypes. A reversion of C4 to C3 photosynthesis during the
evolution of the lineage that includes S. hians is identified. These and other recent results indicate that repeated
reversions from C4 to C3 have occurred. The C3 species Panicum laxum has a strongly supported sister group
relationship to S. hians (C3-C4). The most parsimonious interpretation is that S. hians represents an incipient
reversal from C3 to C4 photosynthesis, beginning with the capacity to compartmentalize photorespiratory
metabolism in the bundle sheath tissue
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Preliminary evaluation of Am/Cm melter feed preparation process upset recovery flowsheets
This document summarizes the results from the development of flowsheets to recover from credible processing errors specified in TTR 99-MNSS/SE-006. The proposed flowsheets were developed in laboratory scale equipment and will be utilized with minor modifications for full scale demonstrations in the Am/Cm Pilot Facility
Phylogenetically Widespread Multiple Paternity in New World Natricine Snakes
We used microsatellite DNA markers to identify the extent to which multiple paternity within litters occurs
among species of New World natricine snakes. We selected seven species to represent the three major clades of
Natricinae and all three subclades of the gartersnake clade. Microsatellite DNA genotyping of dams and litters confirmed
multiple paternity within litters of six species, including Thamnophis radix, T. sauritus, Storeria dekayi, S.
occipitomaculata, Nerodia rhombifer, and Regina septemvittata. Multiple paternity was not evident in one litter of nine
Thamnophis melanogaster. Together with published data documenting multiple paternity in T. bulteri, T. elegans, T.
sirtalis, and N. sipedon, these results confirm the phylogenetically widespread occurrence of multiple paternity among
New World natricines, emphasizing the need to consider phylogenetic (historical) explanations when analyzing snake
mating systems
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