475 research outputs found
Multi-sensor Testing for Automated Rendezvous and Docking
During the past two years, many sensors have been tested in an open-loop fashion in the Marshall Space Flight Center (MSFC) Flight Robotics Laboratory (FRL) to both determine their suitability for use in Automated Rendezvous and Docking (AR&D) systems and to ensure the test facility is prepared for future multi-sensor testing. The primary focus of this work was in support of the CEV AR&D system, because the AR&D sensor technology area was identified as one of the top risks in the program. In 2006, four different sensors were tested individually or in a pair in the MSFC FRL. In 2007, four sensors, two each of two different types, were tested simultaneously. In each set of tests, the target was moved through a series of pre-planned trajectories while the sensor tracked it. In addition, a laser tracker "truth" sensor also measured the target motion. The tests demonstrated the functionality of testing four sensors simultaneously as well as the capabilities (both good and bad) of all of the different sensors tested. This paper outlines the test setup and conditions, briefly describes the facility, summarizes the earlier results of the individual sensor tests, and describes in some detail the results of the four-sensor testing. Post-test analysis includes data fusion by minimum variance estimation and sequential Kalman filtering. This Sensor Technology Project work was funded by NASA's Exploration Technology Development Program
Case History – Monitored Settlement of 32m Thick Compacted Fill
An abandoned brickyard, about 32 m deep, was filled with soil from numerous excavations in the Metro Toronto area with the ultimate intent of development for residential purposes. Compaction and environmental control of the fill was carried out and drainage wells installed to keep the water table low in order to hasten the rate of settlement. The fill generally was placed at approximately 85 percent saturation. A magnetic settlement system was installed as the fill was placed and the differential settlement recorded during fill placement and about 4 years after completion. The rate of settlement response was rapid but proceeded more slowly as the fill became compressed close to the saturated state
Magnetic penetration depth in electron-doped cuprates - evidence for gap nodes
The in-plane penetration depth \lambda(T) is measured in electron-doped
single crystals Nd1.85Ce0.15CuO4-x (NCCO) and Pr1.85Ce0.15CuO4-x (PCCO) using a
11 MHz LC resonator. In NCCO, \lambda(T) exhibits a minimum at 3.8 K and a
pronounced upturn down to 0.4 K due to the paramagnetic contribution of Nd3+
ions. The London penetration depth contribution is linear in T. The
paramagnetic contribution is absent in PCCO, where \lambda(T)~T^2 at low
temperatures. Our results indicate the presence of nodes in the superconducting
gap, i.e., non s-wave symmetry of the order parameter in electron-doped
cuprates.Comment: 2 pages Acrobat-3 optimized PDF. To be presented at M2S-HTSC-V
Multispecies reconstructions uncover widespread conservation, and lineage-specific elaborations in eukaryotic mRNA metabolism.
The degree of conservation and evolution of cytoplasmic mRNA metabolism pathways across the eukaryotes remains incompletely resolved. In this study, we describe a comprehensive genome and transcriptome-wide analysis of proteins involved in mRNA maturation, translation, and mRNA decay across representative organisms from the six eukaryotic super-groups. We demonstrate that eukaryotes share common pathways for mRNA metabolism that were almost certainly present in the last eukaryotic common ancestor, and show for the first time a correlation between intron density and a selective absence of some Exon Junction Complex (EJC) components in eukaryotes. In addition, we identify pathways that have diversified in individual lineages, with a specific focus on the unique gene gains and losses in members of the Excavata and SAR groups that contribute to their unique gene expression pathways compared to other organisms
Computational Study of the Rovibrational Spectrum of COâ‚‚-CSâ‚‚
A new intermolecular potential energy surface, rovibrational transition frequencies, and line strengths are computed for CO2-CS2. the potential is made by fitting energies obtained from explicitly correlated coupled-cluster calculations using an interpolating moving least squares method. the rovibrational Schrödinger equation is solved with a symmetry-adapted Lanczos algorithm and an uncoupled product basis set. All four intermolecular coordinates are included in the calculation. in agreement with previous experiments, the global minimum of the potential energy surface (PES) is cross shaped. the PES also has slipped-parallel minima. Rovibrational wavefunctions are localized in the cross minima and the slipped-parallel minima. Vibrational parent analysis was used to assign vibrational labels to rovibrational states. Tunneling occurs between the two cross minima. Because more than one symmetry operation interconverts the two wells, the symmetry (-oo) of the upper component of the tunneling doublet is different from the symmetry (-ee) of the tunneling coordinate. This unusual situation is due to the multidimensional nature of the double well tunneling. For the cross ground vibrational state, calculated rotational constants differ from their experimental counterparts by less than 0.0001 cm-1. Most rovibrational states were found to be incompatible with the standard effective rotational Hamiltonian often used to fit spectra. This appears to be due to coupling between internal and overall rotation of the dimer. a simple 2D model accounting for internal rotation was used for two cross-shaped fundamentals to obtain good fits
Calculated Vibrational States of Ozone up to Dissociation
A new accurate global potential energy surface for the ground electronic state of ozone [R. Dawes et al., J. Chem. Phys. 139, 201103 (2013)] was published fairly recently. The topography near dissociation differs significantly from previous surfaces, without spurious submerged reefs and corresponding van der Waals wells. This has enabled significantly improved descriptions of scattering processes, capturing the negative temperature dependence and large kinetic isotope effects in exchange reaction rates. The exchange reactivity was found to depend on the character of near-threshold resonances and their overlap with reactant and product wavefunctions, which in turn are sensitive to the potential. Here we present global three-well calculations of all bound vibrational states of three isotopic combinations of ozone (48O3, 16O218O, 16O217O) for J = 0 and J = 1 with a focus on the character and density of highly excited states and discuss their impact on the ozone isotopic anomaly. The calculations were done using a parallel symmetry-adapted Lanczos method with the RV3 code. Some comparisons were made with results obtained with the improved relaxation method implemented in the Heidelberg multi-configuration time-dependent Hartree code
Computational Study of the Ro-Vibrational Spectrum of CO-COâ‚‚
An accurate ab initio ground-state intermolecular potential energy surface (PES) was determined for the CO-CO2 van der Waals dimer. The Lanczos algorithm was used to compute rovibrational energies on this PES. For both the C-in and O-in T-shaped isomers, the fundamental transition frequencies agree well with previous experimental results. We confirm that the in-plane states previously observed are geared states. In addition, we have computed and assigned many other vibrational states. The rotational constants we determine from J = 1 energy levels agree well with their experimental counterparts. Planar and out-of-plane cuts of some of the wavefunctions we compute are quite different, indicating strong coupling between the bend and torsional modes. Because the stable isomers are T-shaped, vibration along the out-of-plane coordinates is very floppy. In CO-CO2, when the molecule is out-of-plane, interconversion of the isomers is possible, but the barrier height is higher than the in-plane geared barrier height
List of Tasmanian Hepaticae
List of sixty Tasmanian Hepaticae
collected by R. A. Bastow, Esq., F.L.S., near Hobart, at Mt Wellington, Mount Nelson, Proctors Road, Huon Road, Jonathans Track, St. Crispin’s Well, and Wellington Falls,
Tasmania, 1885-6 ; and catalogued by B. Carrington, M.D., E.E.S.E.,
and W. H. Pearson, from Eccles, England
Infrared spectrum and intermolecular potential energy surface of the CO-O2 dimer
Only a few weakly-bound complexes containing the O2 molecule have been
characterized by high resolution spectroscopy, no doubt due to the
complications added by the oxygen molecule's unpaired electron spin. Here we
report an extensive infrared spectrum of CO-O2, observed in the CO fundamental
band region using a tunable quantum cascade laser to probe a pulsed supersonic
jet expansion. The rotational energy level pattern derived from the spectrum
consists of stacks of levels characterized by the total angular momentum, J,
and its projection on the intermolecular axis, K. Five such stacks are observed
in the ground vibrational state, and ten in the excited state (v(CO) = 1). They
are divided into two groups, with no observed transitions between groups. The
groups correspond to different projections of the O2 electron spin, and
correlate with the two lowest rotational states of O2, (N, J) = (1, 0) and (1,
2). The rotational constant of the lowest K = 0 stack implies an effective
intermolecular separation of 3.82 Angstroms, but this should be interpreted
with caution since it ignores possible effects of electron spin. A new
high-level 4-dimensional potential energy surface is developed for CO-O2, and
rotational energy levels are calculated for this surface, ignoring electron
spin. By comparing calculated and observed levels, it is possible to assign
detailed quantum labels to the observed level stacks.Comment: 35 pages and 8 figure
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