23,425 research outputs found
Characterization of the near-Earth Asteroid 2002NY40
In August 2002, the near-Earth asteroid 2002 NY40, made its closest approach
to the Earth. This provided an opportunity to study a near-Earth asteroid with
a variety of instruments. Several of the telescopes at the Maui Space
Surveillance System were trained at the asteroid and collected adaptive optics
images, photometry and spectroscopy. Analysis of the imagery reveals the
asteroid is triangular shaped with significant self-shadowing. The photometry
reveals a 20-hour period and the spectroscopy shows that the asteroid is a
Q-type
Comparative analysis of knowledge representation and reasoning requirements across a range of life sciences textbooks.
BackgroundUsing knowledge representation for biomedical projects is now commonplace. In previous work, we represented the knowledge found in a college-level biology textbook in a fashion useful for answering questions. We showed that embedding the knowledge representation and question-answering abilities in an electronic textbook helped to engage student interest and improve learning. A natural question that arises from this success, and this paper's primary focus, is whether a similar approach is applicable across a range of life science textbooks. To answer that question, we considered four different textbooks, ranging from a below-introductory college biology text to an advanced, graduate-level neuroscience textbook. For these textbooks, we investigated the following questions: (1) To what extent is knowledge shared between the different textbooks? (2) To what extent can the same upper ontology be used to represent the knowledge found in different textbooks? (3) To what extent can the questions of interest for a range of textbooks be answered by using the same reasoning mechanisms?ResultsOur existing modeling and reasoning methods apply especially well both to a textbook that is comparable in level to the text studied in our previous work (i.e., an introductory-level text) and to a textbook at a lower level, suggesting potential for a high degree of portability. Even for the overlapping knowledge found across the textbooks, the level of detail covered in each textbook was different, which requires that the representations must be customized for each textbook. We also found that for advanced textbooks, representing models and scientific reasoning processes was particularly important.ConclusionsWith some additional work, our representation methodology would be applicable to a range of textbooks. The requirements for knowledge representation are common across textbooks, suggesting that a shared semantic infrastructure for the life sciences is feasible. Because our representation overlaps heavily with those already being used for biomedical ontologies, this work suggests a natural pathway to include such representations as part of the life sciences curriculum at different grade levels
Spatio-angular Minimum-variance Tomographic Controller for Multi-Object Adaptive Optics systems
Multi-object astronomical adaptive-optics (MOAO) is now a mature wide-field
observation mode to enlarge the adaptive-optics-corrected field in a few
specific locations over tens of arc-minutes.
The work-scope provided by open-loop tomography and pupil conjugation is
amenable to a spatio-angular Linear-Quadratic Gaussian (SA-LQG) formulation
aiming to provide enhanced correction across the field with improved
performance over static reconstruction methods and less stringent computational
complexity scaling laws.
Starting from our previous work [1], we use stochastic time-progression
models coupled to approximate sparse measurement operators to outline a
suitable SA-LQG formulation capable of delivering near optimal correction.
Under the spatio-angular framework the wave-fronts are never explicitly
estimated in the volume,providing considerable computational savings on
10m-class telescopes and beyond.
We find that for Raven, a 10m-class MOAO system with two science channels,
the SA-LQG improves the limiting magnitude by two stellar magnitudes when both
Strehl-ratio and Ensquared-energy are used as figures of merit. The
sky-coverage is therefore improved by a factor of 5.Comment: 30 pages, 7 figures, submitted to Applied Optic
Object-oriented Matlab adaptive optics toolbox
Object-Oriented Matlab Adaptive Optics (OOMAO) is a Matlab toolbox dedicated to Adaptive Optics (AO) systems. OOMAO is based on a small set of classes representing the source, atmosphere, telescope, wavefront sensor, Deformable Mirror (DM) and an imager of an AO system. This simple set of classes allows simulating Natural Guide Star (NGS) and Laser Guide Star (LGS) Single Conjugate AO (SCAO) and tomography AO systems on telescopes up to the size of the Extremely Large Telescopes (ELT). The discrete phase screens that make the atmosphere model can be of infinite size, useful for modeling system performance on large time scales. OOMAO comes with its own parametric influence function model to emulate different types of DMs. The cone effect, altitude thickness and intensity profile of LGSs are also reproduced. Both modal and zonal modeling approach are implemented. OOMAO has also an extensive library of theoretical expressions to evaluate the statistical properties of turbulence wavefronts. The main design characteristics of the OOMAO toolbox are object-oriented modularity, vectorized code and transparent parallel computing. OOMAO has been used to simulate and to design the Multi-Object AO prototype Raven at the Subaru telescope and the Laser Tomography AO system of the Giant Magellan Telescope. In this paper, a Laser Tomography AO system on an ELT is simulated with OOMAO. In the first part, we set-up the class parameters and we link the instantiated objects to create the source optical path. Then we build the tomographic reconstructor and write the script for the pseudo-open-loop controller
FLASH redshift survey - I. Observations and Catalogue
The FLAIR Shapley-Hydra (FLASH) redshift survey catalogue consists of 4613
galaxies brighter than \bJ = 16.7 (corrected for Galactic extinction) over a
605 sq. degree region of sky in the general direction of the Local Group
motion. The survey region is an approximately 60\degr \times 10\degr strip
spanning the sky from the Shapley Supercluster to the Hydra cluster, and
contains 3141 galaxies with measured redshifts. Designed to explore the effect
of the galaxy concentrations in this direction (in particular the Supergalactic
plane and the Shapley Supercluster) upon the Local Group motion, the 68%
completeness allows us to sample the large-scale structure better than similar
sparsely-sampled surveys. The survey region does not overlap with the areas
covered by ongoing wide-angle (Sloan or 2dF) complete redshift surveys. In this
paper, the first in a series, we describe the observation and data reduction
procedures, the analysis for the redshift errors and survey completeness, and
present the survey data.Comment: 12 pages, 12 figures, mn.sty, submitted to MNRA
Normativity all the way down: from normative realism to pannormism
In this paper, I provide an argument for pannormism, the view according to which there are normative properties all the way down. In particular, I argue for what I call the trickling down principle, which says that if there is a metaphysically basic normative property, then, if whatever instantiates it has a ground, that ground instantiates it as well
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