202 research outputs found
Ares I-X Best Estimated Trajectory Analysis and Results
The Ares I-X trajectory reconstruction produced best estimated trajectories of the flight test vehicle ascent through stage separation, and of the first and upper stage entries after separation. The trajectory reconstruction process combines on-board, ground-based, and atmospheric measurements to produce the trajectory estimates. The Ares I-X vehicle had a number of on-board and ground based sensors that were available, including inertial measurement units, radar, air-data, and weather balloons. However, due to problems with calibrations and/or data, not all of the sensor data were used. The trajectory estimate was generated using an Iterative Extended Kalman Filter algorithm, which is an industry standard processing algorithm for filtering and estimation applications. This paper describes the methodology and results of the trajectory reconstruction process, including flight data preprocessing and input uncertainties, trajectory estimation algorithms, output transformations, and comparisons with preflight predictions
Ares I-X Best Estimated Trajectory and Comparison with Pre-Flight Predictions
The Ares I-X trajectory reconstruction produced best estimated trajectories of the flight test vehicle ascent through stage separation, and of the first and upper stage entries after separation. The trajectory reconstruction process combines on-board, ground-based, and atmospheric measurements to produce the trajectory estimates. The Ares I-X vehicle had a number of on-board and ground based sensors that were available, including inertial measurement units, radar, air- data, and weather balloons. However, due to problems with calibrations and/or data, not all of the sensor data were used. The trajectory estimate was generated using an Iterative Extended Kalman Filter algorithm, which is an industry standard processing algorithm for filtering and estimation applications. This paper describes the methodology and results of the trajectory reconstruction process, including flight data preprocessing and input uncertainties, trajectory estimation algorithms, output transformations, and comparisons with preflight predictions
Contemplating Synergistic Algorithms for the NASA ACE Mission
ACE is a proposed Tier 2 NASA Decadal Survey mission that will focus on clouds, aerosols, and precipitation as well as ocean ecosystems. The primary objective of the clouds component of this mission is to advance our ability to predict changes to the Earth's hydrological cycle and energy balance in response to climate forcings by generating observational constraints on future science questions, especially those associated with the effects of aerosol on clouds and precipitation. ACE will continue and extend the measurement heritage that began with the A-Train and that will continue through Earthcare. ACE planning efforts have identified several data streams that can contribute significantly to characterizing the properties of clouds and precipitation and the physical processes that force these properties. These include dual frequency Doppler radar, high spectral resolution lidar, polarimetric visible imagers, passive microwave and submillimeter wave radiometry. While all these data streams are technologically feasible, their total cost is substantial and likely prohibitive. It is, therefore, necessary to critically evaluate their contributions to the ACE science goals. We have begun developing algorithms to explore this trade space. Specifically, we will describe our early exploratory algorithms that take as input the set of potential ACE-like data streams and evaluate critically to what extent each data stream influences the error in a specific cloud quantity retrieval
Temperature Dependent Conformational Transitions and Hydrogen Bond Dynamics of the Elastin-Like Octapeptide GVG(VPGVG): a Molecular Dynamics Study
A joint experimental / theoretical investigation of the elastin-like
octapeptide GVG(VPGVG) was carried out. In this paper a comprehensive molecular
dynamics study of the temperature dependent folding and unfolding of the
octapeptide is presented. The current study, as well as its experimental
counterpart find that this peptide undergoes an "inverse temperature
transition", ITT, leading to a folding at about 310-330 K. In addition, an
unfolding transition is identified at unusually high temperatures approaching
the boiling point of water. Due to the small size of the system two broad
temperature regimes are found: the "ITT regime" (at about 280-320 K) and the
"unfolding regime" at about T > 330 K, where the peptide has a maximum
probability of being folded at approximately 330 K. A detailed molecular
picture involving a thermodynamic order parameter, or reaction coordinate, for
this process is presented along with a time-correlation function analysis of
the hydrogen bond dynamics within the peptide as well as between the peptide
and solvating water molecules. Correlation with experimental evidence and
ramifications on the properties of elastin are discussed.Comment: 15 pages, 1 table, 8 figure
Type IIb Supernova SN 2011dh: Spectra and Photometry from the Ultraviolet to the Near-Infrared
We report spectroscopic and photometric observations of the Type IIb SN
2011dh obtained between 4 and 34 days after the estimated date of explosion
(May 31.5 UT). The data cover a wide wavelength range from 2,000 Angstroms in
the UV to 2.4 microns in the NIR. Optical spectra provide line profiles and
velocity measurements of HI, HeI, CaII and FeII that trace the composition and
kinematics of the SN. NIR spectra show that helium is present in the atmosphere
as early as 11 days after the explosion. A UV spectrum obtained with the STIS
reveals that the UV flux for SN 2011dh is low compared to other SN IIb. The HI
and HeI velocities in SN 2011dh are separated by about 4,000 km/s at all
phases. We estimate that the H-shell of SN 2011dh is about 8 times less massive
than the shell of SN 1993J and about 3 times more massive than the shell of SN
2008ax. Light curves (LC) for twelve passbands are presented. The maximum
bolometric luminosity of erg s occurred
about 22 days after the explosion. NIR emission provides more than 30% of the
total bolometric flux at the beginning of our observations and increases to
nearly 50% of the total by day 34. The UV produces 16% of the total flux on day
4, 5% on day 9 and 1% on day 34. We compare the bolometric light curves of SN
2011dh, SN 2008ax and SN 1993J. The LC are very different for the first twelve
days after the explosions but all three SN IIb display similar peak
luminosities, times of peak, decline rates and colors after maximum. This
suggests that the progenitors of these SN IIb may have had similar compositions
and masses but they exploded inside hydrogen shells that that have a wide range
of masses. The detailed observations presented here will help evaluate
theoretical models for this supernova and lead to a better understanding of SN
IIb.Comment: 23 pages, 14 figures, 9 tables, accepted by Ap
Variants in Doublecortin- and Calmodulin Kinase Like 1, a Gene Up-Regulated by BDNF, Are Associated with Memory and General Cognitive Abilities
Human memory and general cognitive abilities are complex functions of high heritability and wide variability in the population. The brain-derived neurotrophic factor (BDNF) plays an important role in mammalian memory formation.Based on the identification of genes markedly up-regulated during BDNF-induced synaptic consolidation in the hippocampus, we selected genetic variants that were tested in three independent samples, from Norway and Scotland, of adult individuals examined for cognitive abilities. In all samples, we show that markers in the doublecortin- and calmodulin kinase like 1 (DCLK1) gene, are significantly associated with general cognition (IQ scores) and verbal memory function, resisting multiple testing. DCLK1 is a complex gene with multiple transcripts which vary in expression and function. We show that the short variants are all up-regulated after BDNF treatment in the rat hippocampus, and that they are expressed in the adult human brain (mostly in cortices and hippocampus). We demonstrate that several of the associated variants are located in potential alternative promoter- and cis-regulatory elements of the gene and that they affect BDNF-mediated expression of short DCLK1 transcripts in a reporter system.These data present DCLK1 as a functionally pertinent gene involved in human memory and cognitive functions
PTF10fqs: A Luminous Red Nova in the Spiral Galaxy Messier 99
The Palomar Transient Factory (PTF) is systematically charting the optical
transient and variable sky. A primary science driver of PTF is building a
complete inventory of transients in the local Universe (distance less than 200
Mpc). Here, we report the discovery of PTF10fqs, a transient in the luminosity
"gap" between novae and supernovae. Located on a spiral arm of Messier 99, PTF
10fqs has a peak luminosity of Mr = -12.3, red color (g-r = 1.0) and is slowly
evolving (decayed by 1 mag in 68 days). It has a spectrum dominated by
intermediate-width H (930 km/s) and narrow calcium emission lines. The
explosion signature (the light curve and spectra) is overall similar to thatof
M85OT2006-1, SN2008S, and NGC300OT. The origin of these events is shrouded in
mystery and controversy (and in some cases, in dust). PTF10fqs shows some
evidence of a broad feature (around 8600A) that may suggest very large
velocities (10,000 km/s) in this explosion. Ongoing surveys can be expected to
find a few such events per year. Sensitive spectroscopy, infrared monitoring
and statistics (e.g. disk versus bulge) will eventually make it possible for
astronomers to unravel the nature of these mysterious explosions.Comment: 12 pages, 12 figures, Replaced with published versio
Anticholinergic Drugs in Late Life: Adverse Effects on Cognition but not on Progress to Dementia
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