Image improvement from a sodium-layer laser guide star adaptive optics system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Max, C. E., LLNL

1997-06-01

A sodium-layer laser guide star beacon with high-order adaptive optics at Lick Observatory produced a factor of 2.4 intensity increase and a factor of 2 decrease in full width at half maximum for an astronomical point source, compared with image motion compensation alone. Image full widths at half maximum were identical for laser and natural guide stars (0.3 arc seconds). The Strehl ratio with the laser guide star was 65% of that with a natural guide star. This technique should allow ground-based telescopes to attain the diffraction limit, by correcting for atmospheric distortions.

Simulations of vortices in a star-shaped plate with an artificial pin

NASA Astrophysics Data System (ADS)

Miyoshi, Hiroki; Ito, Atsuki; Dang, Vu The; Thanh Huy, Ho; Hayashi, Masahiko; Kato, Masaru; Ishida, Takekazu

2017-07-01

Although a triangular vortex lattice is stable in a bulk type-II superconductor, exotic vortex configurations are expected to appear in a small superconducting plate. Theoretical calculations on vortex structures in a star-shaped superconducting plate have been given in our preceding work. In this work, we extended our theoretical studies to the case of having an artificial pin. We performed the Ginzburg-Landau (GL) calculations systematically to compare with the pin-free case by using the finite element method. We found that a vortex tends to accommodate preferentially in an aritificial pin in the star-shaped plate. We found a systematic evolution of vortex structure with increaseing magnetic field. We compare our theoretical calculations with vortices in a star-shaped Mo80Ge20 plate with an artificial pin and without an artificial pin obtained by a scanning SQUID microscope. We reconstructed the vortex image on the sample surface by using the inverse Biot-Savart law and the Fourier transformation.

Initial results from the Lick Observatory Laser Guide Star Adaptive Optics System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olivier, S.S.; An, J.; Avicola, K.

1995-11-08

A prototype adaptive optics system has been installed and tested on the 3 m Shane telescope at Lick Observatory. The adaptive optics system performance, using bright natural guide stars, is consistent with expectations based on theory. A sodium-layer laser guide star system has also been installed and tested on the Shane telescope. Operating at 15 W, the laser system produces a 9th magnitude guide star with seeing-limited size at 589 nm. Using the laser guide star, the adaptive optics system has reduced the wavefront phase variance on scales above 50 cm by a factor of 4. These results represent themore » first continuous wavefront phase correction using a sodium-layer laser guide star. Assuming tip-tilt is removed using a natural guide star, the measured control loop performance should produce images with a Strehl ratio of 0.4 at 2.2 {mu}m in 1 arc second seeing. Additional calibration procedures must be implemented in order to achieve these results with the prototype Lick adaptive optics system.« less

First results of a polychromatic artificial sodium star for the correction of tilt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedman, H.; Foy, R..; Tallon, M.

1996-03-06

This paper presents the first results of a joint experiment carried out at Lawrence Livermore National Laboratory during January, 1996. Laser and optical systems were tested to provide a polychromatic artificial sodium star for the correction of tilt. This paper presents the results of that experiment.

ARGOS - the Laser Star Adaptive Optics for LBT

NASA Astrophysics Data System (ADS)

Rabien, S.; Barl, L.; Beckmann, U.; Blümchen, T.; Bonaglia, M.; Borelli, J. L.; Brynnel, J.; Busoni, L.; Carbonaro, L.; Conot, C.; Davies, R.; Deysenroth, M.; Durney, O.; Elberich, M.; Esposito, S.; Gasho, V.; Gässler, W.; Gemperlein, H.; Genzel, R.; Green, R.; Haug, M.; Lloyd Hart, M.; Hubbard, P.; Kanneganti, S.; Kulas, M.; Noenickx, J.; Peter, D.; Quirrenbach, A.; Rademacher, M.; Rix, H. W.; Salinari, P.; Schwab, C.; Storm, J.; Strüder, L.; Thiel, M.; Weigelt, G.; Ziegleder, J.; Orban de Xivry, G.

2011-09-01

We will present the design and status of ARGOS - the Laser Guide Star adaptive optics facility for the Large Binocular Telescope. By projecting a constellation of multiple laser guide stars above each of the 8.4m primary mirrors of the LBT, ARGOS in its ground layer mode will enable a wide field adaptive optics correction for multi object spectroscopy. ARGOS implements high power pulsed green lasers and makes use of Rayleigh scattering for the guide star creation. The geometric relations of this setup in guide star height vs. primary diameter are quite comparable to an ELT with sodium guide stars. The use of LBT's adaptive secondary mirror, gated wavefront sensors, a prime focus calibration system and the laser constellation shows several aspects that may be used as pathfinding technology for the planned ELTs. In already planned upgrade steps with a hybrid Sodium-Rayleigh combination ARGOS will enable MCAO and MOAO implementations at LBT allowing unique astronomical observations.

UKIRT fast guide system improvements

NASA Astrophysics Data System (ADS)

Balius, Al; Rees, Nicholas P.

1997-09-01

The United Kingdom Infra-Red Telescope (UKIRT) has recently undergone the first major upgrade program since its construction. One part of the upgrade program was an adaptive tip-tilt secondary mirror closed with a CCD system collectively called the fast guide system. The installation of the new secondary and associated systems was carried out in the first half of 1996. Initial testing of the fast guide system has shown great improvement in guide accuracy. The initial installation included a fixed integration time CCD. In the first part of 1997 an integration time controller based on computed guide star luminosity was implemented in the fast guide system. Also, a Kalman type estimator was installed in the image tracking loop based on a dynamic model and knowledge of the statistical properties of the guide star position error measurement as a function of computed guide star magnitude and CCD integration time. The new configuration was tested in terms of improved guide performance nd graceful degradation when tracking faint guide stars. This paper describes the modified fast guide system configuration and reports the results of performance tests.

Bringing the Visible Universe into Focus with Robo-AO

PubMed Central

Baranec, Christoph; Riddle, Reed; Law, Nicholas M.; Ramaprakash, A.N.; Tendulkar, Shriharsh P.; Bui, Khanh; Burse, Mahesh P.; Chordia, Pravin; Das, Hillol K.; Davis, Jack T.C.; Dekany, Richard G.; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Morton, Timothy D.; Ofek, Eran O.; Punnadi, Sujit

2013-01-01

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes - even telescopes with four times the diameter of HST - appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images. The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled1. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system2,3 employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope. PMID:23426078

Bringing the visible universe into focus with Robo-AO.

PubMed

Baranec, Christoph; Riddle, Reed; Law, Nicholas M; Ramaprakash, A N; Tendulkar, Shriharsh P; Bui, Khanh; Burse, Mahesh P; Chordia, Pravin; Das, Hillol K; Davis, Jack T C; Dekany, Richard G; Kasliwal, Mansi M; Kulkarni, Shrinivas R; Morton, Timothy D; Ofek, Eran O; Punnadi, Sujit

2013-02-12

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes--even telescopes with four times the diameter of HST--appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images. The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system, employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope.

3D artificial bones for bone repair prepared by computed tomography-guided fused deposition modeling for bone repair.

PubMed

Xu, Ning; Ye, Xiaojian; Wei, Daixu; Zhong, Jian; Chen, Yuyun; Xu, Guohua; He, Dannong

2014-09-10

The medical community has expressed significant interest in the development of new types of artificial bones that mimic natural bones. In this study, computed tomography (CT)-guided fused deposition modeling (FDM) was employed to fabricate polycaprolactone (PCL)/hydroxyapatite (HA) and PCL 3D artificial bones to mimic natural goat femurs. The in vitro mechanical properties, in vitro cell biocompatibility, and in vivo performance of the artificial bones in a long load-bearing goat femur bone segmental defect model were studied. All of the results indicate that CT-guided FDM is a simple, convenient, relatively low-cost method that is suitable for fabricating natural bonelike artificial bones. Moreover, PCL/HA 3D artificial bones prepared by CT-guided FDM have more close mechanics to natural bone, good in vitro cell biocompatibility, biodegradation ability, and appropriate in vivo new bone formation ability. Therefore, PCL/HA 3D artificial bones could be potentially be of use in the treatment of patients with clinical bone defects.

Four generations of sodium guide star lasers for adaptive optics in astronomy and space situational awareness

NASA Astrophysics Data System (ADS)

d'Orgeville, Céline; Fetzer, Gregory J.

2016-07-01

This paper recalls the history of sodium guide star laser systems used in astronomy and space situational awareness adaptive optics, analyzing the impact that sodium laser technology evolution has had on routine telescope operations. While it would not be practical to describe every single sodium guide star laser system developed to date, it is possible to characterize their evolution in broad technology terms. The first generation of sodium lasers used dye laser technology to create the first sodium laser guide stars in Hawaii, California, and Spain in the late 1980s and 1990s. These experimental systems were turned into the first laser guide star facilities to equip mediumto- large diameter adaptive optics telescopes, opening a new era of Laser Guide Star Adaptive Optics (LGS AO)-enabled diffraction-limited imaging from the ground. Although they produced exciting scientific results, these laser guide star facilities were large, power-hungry and messy. In the USA, a second-generation of sodium lasers was developed in the 2000s that used cleaner, yet still large and complex, solid-state laser technology. These are the systems in routine operation at the 8 to 10m-class astronomical telescopes and 4m-class satellite imaging facilities today. Meanwhile in Europe, a third generation of sodium lasers was being developed using inherently compact and efficient fiber laser technology, and resulting in the only commercially available sodium guide star laser system to date. Fiber-based sodium lasers are being or will soon be deployed at three astronomical telescopes and two space surveillance stations. These highly promising systems are still relatively large to install on telescopes and they remain significantly expensive to procure and maintain. We are thus proposing to develop a fourth generation of sodium lasers: based on semiconductor technology, these lasers could provide a definitive solution to the problem of sodium LGS AO laser sources for all astronomy and space situational awareness applications.

From Dye Laser Factory to Portable Semiconductor Laser: Four Generations of Sodium Guide Star Lasers for Adaptive Optics in Astronomy and Space Situational Awareness

NASA Astrophysics Data System (ADS)

d'Orgeville, C.; Fetzer, G.

This presentation recalls the history of sodium guide star laser systems used in astronomy and space situational awareness adaptive optics, analysing the impact that sodium laser technology evolution has had on routine telescope operations. While it would not be practical to describe every single sodium guide star laser system developed to date, it is possible to characterize their evolution in broad technology terms. The first generation of sodium lasers used dye laser technology to create the first sodium laser guide stars in Hawaii, California, and Spain in the late 1980's and 1990's. These experimental systems were turned into the first laser guide star facilities to equip medium-to-large diameter adaptive optics telescopes, opening a new era of LGS AO-enabled diffraction-limited imaging from the ground. Although they produced exciting scientific results, these laser guide star facilities were large, power-hungry and messy. In the USA, a second-generation of sodium lasers was developed in the 2000's that used cleaner, yet still large and complex, solid-state laser technology. These are the systems in routine operation at the 8-10m class astronomical telescopes and 4m-class satellite imaging facilities today. Meanwhile in Europe, a third generation of sodium lasers was being developed using inherently compact and efficient fiber laser technology, and resulting in the only commercially available sodium guide star laser system to date. Fiber-based sodium lasers will be deployed at two astronomical telescopes and at least one space debris tracking station this year. Although highly promising, these systems remain significantly expensive and they have yet to demonstrate high performance in the field. We are proposing to develop a fourth generation of sodium lasers: based on semiconductor technology, these lasers could provide the final solution to the problem of sodium laser guide star adaptive optics for all astronomy and space situational awareness applications.

Artificial Satellites Observations Using the Complex of Telescopes of RI "MAO"

NASA Astrophysics Data System (ADS)

Sybiryakova, Ye. S.; Shulga, O. V.; Vovk, V. S.; Kaliuzny, M. P.; Bushuev, F. I.; Kulichenko, M. O.; Haloley, M. I.; Chernozub, V. M.

2017-02-01

Special methods, means and software for cosmic objects' observation and processing of obtained results were developed. Combined method, which consists in separated accumulation of images of reference stars and artificial objects, is the main method used in observations of artificial cosmic objects. It is used for observations of artificial objects at all types of orbits.

Artificial Immune System for Recognizing Patterns

NASA Technical Reports Server (NTRS)

Huntsberger, Terrance

2005-01-01

A method of recognizing or classifying patterns is based on an artificial immune system (AIS), which includes an algorithm and a computational model of nonlinear dynamics inspired by the behavior of a biological immune system. The method has been proposed as the theoretical basis of the computational portion of a star-tracking system aboard a spacecraft. In that system, a newly acquired star image would be treated as an antigen that would be matched by an appropriate antibody (an entry in a star catalog). The method would enable rapid convergence, would afford robustness in the face of noise in the star sensors, would enable recognition of star images acquired in any sensor or spacecraft orientation, and would not make an excessive demand on the computational resources of a typical spacecraft. Going beyond the star-tracking application, the AIS-based pattern-recognition method is potentially applicable to pattern- recognition and -classification processes for diverse purposes -- for example, reconnaissance, detecting intruders, and mining data.

Performance of laser guide star adaptive optics at Lick Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olivier, S.S.; An, J.; Avicola, K.

1995-07-19

A sodium-layer laser guide star adaptive optics system has been developed at Lawrence Livermore National Laboratory (LLNL) for use on the 3-meter Shane telescope at Lick Observatory. The system is based on a 127-actuator continuous-surface deformable mirror, a Hartmann wavefront sensor equipped with a fast-framing low-noise CCD camera, and a pulsed solid-state-pumped dye laser tuned to the atomic sodium resonance line at 589 nm. The adaptive optics system has been tested on the Shane telescope using natural reference stars yielding up to a factor of 12 increase in image peak intensity and a factor of 6.5 reduction in image fullmore » width at half maximum (FWHM). The results are consistent with theoretical expectations. The laser guide star system has been installed and operated on the Shane telescope yielding a beam with 22 W average power at 589 nm. Based on experimental data, this laser should generate an 8th magnitude guide star at this site, and the integrated laser guide star adaptive optics system should produce images with Strehl ratios of 0.4 at 2.2 {mu}m in median seeing and 0.7 at 2.2 {mu}m in good seeing.« less

A Large-Telescope Natural Guide Star AO System

NASA Technical Reports Server (NTRS)

Redding, David; Milman, Mark; Needels, Laura

1994-01-01

None given. From overview and conclusion:Keck Telescope case study. Objectives-low cost, good sky coverage. Approach--natural guide star at 0.8um, correcting at 2.2um.Concl- Good performance is possible for Keck with natural guide star AO system (SR>0.2 to mag 17+).AO-optimized CCD should b every effective. Optimizing td is very effective.Spatial Coadding is not effective except perhaps at extreme low light levels.

Sky coverage modeling for the whole sky for laser guide star multiconjugate adaptive optics.

PubMed

Wang, Lianqi; Andersen, David; Ellerbroek, Brent

2012-06-01

The scientific productivity of laser guide star adaptive optics systems strongly depends on the sky coverage, which describes the probability of finding natural guide stars for the tip/tilt wavefront sensor(s) to achieve a certain performance. Knowledge of the sky coverage is also important for astronomers planning their observations. In this paper, we present an efficient method to compute the sky coverage for the laser guide star multiconjugate adaptive optics system, the Narrow Field Infrared Adaptive Optics System (NFIRAOS), being designed for the Thirty Meter Telescope project. We show that NFIRAOS can achieve more than 70% sky coverage over most of the accessible sky with the requirement of 191 nm total rms wavefront.

Polarization switching of sodium guide star laser for brightness enhancement

NASA Astrophysics Data System (ADS)

Fan, Tingwei; Zhou, Tianhua; Feng, Yan

2016-07-01

The efficiency of optical pumping that enhances the brightness of sodium laser guide star with circularly polarized light is reduced substantially due to the precession of sodium atoms in geomagnetic field. Switching the laser between left and right circular polarization at the Larmor frequency is proposed to improve the photon return. With ESO's cw laser guide star system at Paranal as example, numerical simulation for both square-wave and sine-wave polarization modulation is conducted. For the square-wave switching case, the return flux is increased when the angle between geomagnetic field and laser beam is larger than 60°, as much as 40% at 90°. The method can also be applied for remote measurement of magnetic field with available cw guide star laser.

Guide star targeting success for the HEAO-B observatory

NASA Technical Reports Server (NTRS)

Farrenkopf, R. L.; Hoffman, D. P.

1977-01-01

The statistics associated with the successful selection and acquisition of guide stars as attitude benchmarks for use in reorientation maneuvers of the HEAO-B observatory are considered as a function of the maneuver angle, initial attitude uncertainties, and the pertinent celestial region. Success likelihoods in excess of 0.99 are predicted assuming anticipated gyro and star tracker error sources. The maneuver technique and guide star selection constraints are described in detail. The results presented are specialized numerically to the HEAO-B observatory. However, the analytical techniques developed are considered applicable to broader classes of spacecraft requiring celestial targeting.

Guide-star-based computational adaptive optics for broadband interferometric tomography

PubMed Central

Adie, Steven G.; Shemonski, Nathan D.; Graf, Benedikt W.; Ahmad, Adeel; Scott Carney, P.; Boppart, Stephen A.

2012-01-01

We present a method for the numerical correction of optical aberrations based on indirect sensing of the scattered wavefront from point-like scatterers (“guide stars”) within a three-dimensional broadband interferometric tomogram. This method enables the correction of high-order monochromatic and chromatic aberrations utilizing guide stars that are revealed after numerical compensation of defocus and low-order aberrations of the optical system. Guide-star-based aberration correction in a silicone phantom with sparse sub-resolution-sized scatterers demonstrates improvement of resolution and signal-to-noise ratio over a large isotome. Results in highly scattering muscle tissue showed improved resolution of fine structure over an extended volume. Guide-star-based computational adaptive optics expands upon the use of image metrics for numerically optimizing the aberration correction in broadband interferometric tomography, and is analogous to phase-conjugation and time-reversal methods for focusing in turbid media. PMID:23284179

Atmospheric turbulence compensation with laser phase shifting interferometry

NASA Astrophysics Data System (ADS)

Rabien, S.; Eisenhauer, F.; Genzel, R.; Davies, R. I.; Ott, T.

2006-04-01

Laser guide stars with adaptive optics allow astronomical image correction in the absence of a natural guide star. Single guide star systems with a star created in the earth's sodium layer can be used to correct the wavefront in the near infrared spectral regime for 8-m class telescopes. For possible future telescopes of larger sizes, or for correction at shorter wavelengths, the use of a single guide star is ultimately limited by focal anisoplanatism that arises from the finite height of the guide star. To overcome this limitation we propose to overlap coherently pulsed laser beams that are expanded over the full aperture of the telescope, traveling upwards along the same path which light from the astronomical object travels downwards. Imaging the scattered light from the resultant interference pattern with a camera gated to a certain height above the telescope, and using phase shifting interferometry we have found a method to retrieve the local wavefront gradients. By sensing the backscattered light from two different heights, one can fully remove the cone effect, which can otherwise be a serious handicap to the use of laser guide stars at shorter wavelengths or on larger telescopes. Using two laser beams multiconjugate correction is possible, resulting in larger corrected fields. With a proper choice of laser, wavefront correction could be expanded to the visible regime and, due to the lack of a cone effect, the method is applicable to any size of telescope. Finally the position of the laser spot could be imaged from the side of the main telescope against a bright background star to retrieve tip-tilt information, which would greatly improve the sky coverage of the system.

Fourier domain preconditioned conjugate gradient algorithm for atmospheric tomography.

PubMed

Yang, Qiang; Vogel, Curtis R; Ellerbroek, Brent L

2006-07-20

By 'atmospheric tomography' we mean the estimation of a layered atmospheric turbulence profile from measurements of the pupil-plane phase (or phase gradients) corresponding to several different guide star directions. We introduce what we believe to be a new Fourier domain preconditioned conjugate gradient (FD-PCG) algorithm for atmospheric tomography, and we compare its performance against an existing multigrid preconditioned conjugate gradient (MG-PCG) approach. Numerical results indicate that on conventional serial computers, FD-PCG is as accurate and robust as MG-PCG, but it is from one to two orders of magnitude faster for atmospheric tomography on 30 m class telescopes. Simulations are carried out for both natural guide stars and for a combination of finite-altitude laser guide stars and natural guide stars to resolve tip-tilt uncertainty.

Artificial Intelligence and NASA Data Used to Discover Eighth Planet Circling Distant Star

NASA Image and Video Library

2017-12-12

Our solar system now is tied for most number of planets around a single star, with the recent discovery of an eighth planet circling Kepler-90, a Sun-like star 2,545 light years from Earth. The planet was discovered in data from NASA’s Kepler space telescope. The newly-discovered Kepler-90i -- a sizzling hot, rocky planet that orbits its star once every 14.4 days -- was found by researchers from Google and The University of Texas at Austin using machine learning. Machine learning is an approach to artificial intelligence in which computers “learn.” In this case, computers learned to identify planets by finding in Kepler data instances where the telescope recorded signals from planets beyond our solar system, known as exoplanets. Video Credit: NASA Ames Research Center / Google

Single Fiber Star Couplers. [optical waveguides for spacecraft communication

NASA Technical Reports Server (NTRS)

Asawa, C. K.

1979-01-01

An ion exchange process was developed and used in the fabrication of state-of-the-art planar star couplers for distribution of optical radiation between optical fibers. An 8 x 8 planar transmission star coupler was packaged for evaluation purposes with sixteen fiber connectors and sixteen pigtails. Likewise a transmission star coupler and an eight-port reflection star coupler with eight-fiber ribbons rigidly attached to these couplers, and a planar coupler with silicon guides and a parallel channel guide with pigtails were also fabricated. Optical measurements of the transmission star couplers are included with a description of the manufacturing process.

Adaptive optics program update at TMT

NASA Astrophysics Data System (ADS)

Boyer, C.; Ellerbroek, B.

2016-07-01

The TMT first light AO facility consists of the Narrow Field Infra-Red AO System (NFIRAOS), the associated Laser Guide Star Facility (LGSF) and the AO Executive Software (AOESW). Design, fabrication and prototyping activities of the TMT first light AO systems and their components have significantly ramped up in Canada, China, France, and in the US. NFIRAOS is an order 60 x 60 laser guide star (LGS) multi-conjugate AO (MCAO) system, which provides uniform, diffraction-limited performance in the J, H, and K bands over 34 x 34 arc sec fields with 50 per cent sky coverage at the galactic pole, as required to support the TMT science cases. NFIRAOS includes two deformable mirrors, six laser guide star wavefront sensors, one high order Pyramid WFS for natural guide star AO, and up to three low-order, IR, natural guide star on-instrument wavefront sensors (OIWFS) and four on-detector guide windows (ODGW) within each client instrument. The first light LGSF system includes six sodium lasers to generate the NFIRAOS laser guide stars. In this paper, we will provide an update on the progress in designing, prototyping, fabricating and modeling the TMT first light AO systems and their AO components over the last two years. TMT is continuing with detailed AO modeling to support the design and development of the first light AO systems and components. Major modeling topics studied during the last two years include further studies in the area of pyramid wavefront sensing, high precision astrometry, PSF reconstruction for LGS MCAO, LGSF wavefront error budget and sophisticated low order mode temporal filtering.

Stellar occultation candidates from the guide star catalog. I - Saturn, 1991-1999

NASA Technical Reports Server (NTRS)

Bosh, A. S.; Mcdonald, S. W.

1992-01-01

A list of 203 potential occultations by Saturn and its ring of stars from the HST Guide Star Catalog (GSC) during the years 1991-1999 is presented. This list features many fainter candidates than do current occultation candidate lists for Saturn; these fainter stars can also provide a high signal-to-noise ratio if observed with a large telescope or in the IR where Saturn and its rings have absorption bands. The occultation circumstances are listed, as well as star information found in the GSC.

Natural guide-star processing for wide-field laser-assisted AO systems

NASA Astrophysics Data System (ADS)

Correia, Carlos M.; Neichel, Benoit; Conan, Jean-Marc; Petit, Cyril; Sauvage, Jean-Francois; Fusco, Thierry; Vernet, Joel D. R.; Thatte, Niranjan

2016-07-01

Sky-coverage in laser-assisted AO observations largely depends on the system's capability to guide on the faintest natural guide-stars possible. Here we give an up-to-date status of our natural guide-star processing tailored to the European-ELT's visible and near-infrared (0.47 to 2.45 μm) integral field spectrograph - Harmoni. We tour the processing of both the isoplanatic and anisoplanatic tilt modes using the spatio-angular approach whereby the wavefront is estimated directly in the pupil plane avoiding a cumbersome explicit layered estimation on the 35-layer profiles we're currently using. Taking the case of Harmoni, we cover the choice of wave-front sensors, the number and field location of guide-stars, the optimised algorithms to beat down angular anisoplanatism and the performance obtained with different temporal controllers under split high-order/low-order tomography or joint tomography. We consider both atmospheric and far greater telescope wind buffeting disturbances. In addition we provide the sky-coverage estimates thus obtained.

Transforming GSC-II Magnitudes into JWST/FGS Count Rates

NASA Astrophysics Data System (ADS)

Holfeltz, Sherie T.; Chayer, P.; Nelan, E. P.

2010-01-01

The JWST Fine Guidance Sensor (FGS) will provide the positions of guide stars to the spacecraft attitude control system to facilitate the fine pointing of the Observatory. The FGS is an infrared camera operating in an unfiltered passband from 0.6 to 5.3 microns. The ground system will select guide stars from the Guide Star Catalog II (GSC-II), which is an all-sky catalog with three optical passbands (BJ, RF, IN) derived from photographic plates, and from 2MASS. We present a method for predicting a guide star's FGS photon count rate, which is needed to operate the FGS. The method consists of first deriving equations for transforming the GSC-II optical passbands into J, H, and K for stars that are below the 2MASS faint limiting magnitude, based upon fitting the distribution of brighter stars in color-color diagrams using GSC-II and 2MASS photometry. Next, we convolve the BJ, RF, IN and predicted J, H, and K magnitudes (or 2MASS magnitudes if available) for a given star with the wavelength dependent throughput and sensitivity of the telescope and FGS. To estimate the accuracy of this method for stars that are too faint for 2MASS, we compare the predicted J, H, and K magnitudes for a large sample of stars to data from the United Kingdom Infrared Telescope (UKIRT) Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Using synthetic magnitudes computed from Kurucz models for stars of different spectral types, we show that the method should provide reliable FGS count rates.

The Polychromatic Laser Guide Star: the ELP-OA demonstrator at Observatoire de Haute Provence

NASA Astrophysics Data System (ADS)

Foy, R.; Chatagnat, M.; Dubet, D.; Éric, P.; Eysseric, J.; Foy, F.-C.; Fusco, T.; Girard, J.; Laloge, A.; Le van Suu, A.; Messaoudi, B.; Perruchot, S.; Richaud, P.; Richaud, Y.; Rondeau, X.; Tallon, M.; Thiébaut, É.; Boër, M.

2007-07-01

The correction of the tilt for adaptive optics devices from the only laser guide star can be done with the polychromatic laser guide star. We report the progress of the first demonstrator of the implementation of this concept, at Observatoire de Haute-Provence. We review the last steps of the feasibility studies, the optimization of the laser parameters, and the studies of the implementation at the OHP 1.52m telescope, including the beam propagation to the lasers room to the mesosphere and the algorithms for tip-tilt measurements.

Guide star probabilities

NASA Technical Reports Server (NTRS)

Soneira, R. M.; Bahcall, J. N.

1981-01-01

Probabilities are calculated for acquiring suitable guide stars (GS) with the fine guidance system (FGS) of the space telescope. A number of the considerations and techniques described are also relevant for other space astronomy missions. The constraints of the FGS are reviewed. The available data on bright star densities are summarized and a previous error in the literature is corrected. Separate analytic and Monte Carlo calculations of the probabilities are described. A simulation of space telescope pointing is carried out using the Weistrop north galactic pole catalog of bright stars. Sufficient information is presented so that the probabilities of acquisition can be estimated as a function of position in the sky. The probability of acquiring suitable guide stars is greatly increased if the FGS can allow an appreciable difference between the (bright) primary GS limiting magnitude and the (fainter) secondary GS limiting magnitude.

Design of an holographic off-axis calibration light source for ARGOS at the LBT

NASA Astrophysics Data System (ADS)

Schwab, Christian; Gassler, Wolfgang; Peter, Diethard; Blumchen, Thomas; Aigner, Simon; Quirrenbach, Andreas

We report on the design of an artificial light source for ARGOS, the multiple Rayleigh laser guide star (LGS) facility at the Large Binocular Telescope (LBT). Our light source mimics the expected night-time illumination of the adaptive secondary mirror (ASM) by the laser beacons very accurately and provides a way to check the achieved performance, allowing thorough testing of the system during day time. The optical design makes use of computer generated holograms (CGH) and strong aspheres to achieve a very small residual wavefront error. Additional structures on the CGH facilitate quick and precise alignment of the optics in the prime focus. We demonstrate that the scheme can be applied to the current European Extremely Large Telescope (E-ELT) design in a similar way.

ARGOS wavefront sensing: from detection to correction

NASA Astrophysics Data System (ADS)

Orban de Xivry, Gilles; Bonaglia, M.; Borelli, J.; Busoni, L.; Connot, C.; Esposito, S.; Gaessler, W.; Kulas, M.; Mazzoni, T.; Puglisi, A.; Rabien, S.; Storm, J.; Ziegleder, J.

2014-08-01

Argos is the ground-layer adaptive optics system for the Large Binocular Telescope. In order to perform its wide-field correction, Argos uses three laser guide stars which sample the atmospheric turbulence. To perform the correction, Argos has at disposal three different wavefront sensing measurements : its three laser guide stars, a NGS tip-tilt, and a third wavefront sensor. We present the wavefront sensing architecture and its individual components, in particular: the finalized Argos pnCCD camera detecting the 3 laser guide stars at 1kHz, high quantum efficiency and 4e- noise; the Argos tip-tilt sensor based on a quad-cell avalanche photo-diodes; and the Argos wavefront computer. Being in the middle of the commissioning, we present the first wavefront sensing configurations and operations performed at LBT, and discuss further improvements in the measurements of the 3 laser guide star slopes as detected by the pnCCD.

Space-Based Astronomy: An Educator Guide with Activities for Science, Mathematics, and Technology Education

NASA Technical Reports Server (NTRS)

Vogt, Gregory L.

2001-01-01

If you go to the country, far from city lights, you can see about 3,000 stars on a clear night. If your eyes were bigger, you could see many more stars. With a pair of binoculars, an optical device that effectively enlarges the pupil of your eye by about 30 times, the number of stars you can see increases to the tens of thousands. With a medium-sized telescope with a light-collecting mirror 30 centimeters in diameter, you can see hundreds of thousands of stars. With a large observatory telescope, millions of stars become visible. This curriculum guide uses hands-on activities to help students and teachers understand the significance of space-based astronomy--astronomical observations made from outer space. It is not intended to serve as a curriculum. Instead, teachers should select activities from this guide that support and extend existing study. The guide contains few of the traditional activities found in many astronomy guides such as constellation studies, lunar phases, and planetary orbits. It tells, rather, the story of why it is important to observe celestial objects from outer space and how to study the entire electromagnetic spectrum. Teachers are encouraged to adapt these activities for the particular needs of their students. When selected activities from this guide are used in conjunction with traditional astronomy curricula, students benefit from a more complete experience.

Near infra-red astronomy with adaptive optics and laser guide stars at the Keck Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Max, C.E.; Gavel, D.T.; Olivier, S.S.

1995-08-03

A laser guide star adaptive optics system is being built for the W. M. Keck Observatory`s 10-meter Keck II telescope. Two new near infra-red instruments will be used with this system: a high-resolution camera (NIRC 2) and an echelle spectrometer (NIRSPEC). The authors describe the expected capabilities of these instruments for high-resolution astronomy, using adaptive optics with either a natural star or a sodium-layer laser guide star as a reference. They compare the expected performance of these planned Keck adaptive optics instruments with that predicted for the NICMOS near infra-red camera, which is scheduled to be installed on the Hubblemore » Space Telescope in 1997.« less

StarSmasher: Smoothed Particle Hydrodynamics code for smashing stars and planets

NASA Astrophysics Data System (ADS)

Gaburov, Evghenii; Lombardi, James C., Jr.; Portegies Zwart, Simon; Rasio, F. A.

2018-05-01

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian particle method that approximates a continuous fluid as discrete nodes, each carrying various parameters such as mass, position, velocity, pressure, and temperature. In an SPH simulation the resolution scales with the particle density; StarSmasher is able to handle both equal-mass and equal number-density particle models. StarSmasher solves for hydro forces by calculating the pressure for each particle as a function of the particle's properties - density, internal energy, and internal properties (e.g. temperature and mean molecular weight). The code implements variational equations of motion and libraries to calculate the gravitational forces between particles using direct summation on NVIDIA graphics cards. Using a direct summation instead of a tree-based algorithm for gravity increases the accuracy of the gravity calculations at the cost of speed. The code uses a cubic spline for the smoothing kernel and an artificial viscosity prescription coupled with a Balsara Switch to prevent unphysical interparticle penetration. The code also implements an artificial relaxation force to the equations of motion to add a drag term to the calculated accelerations during relaxation integrations. Initially called StarCrash, StarSmasher was developed originally by Rasio.

Synthetic guide star generation

DOEpatents

Payne, Stephen A [Castro Valley, CA; Page, Ralph H [Castro Valley, CA; Ebbers, Christopher A [Livermore, CA; Beach, Raymond J [Livermore, CA

2008-06-10

A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

Synthetic guide star generation

DOEpatents

Payne, Stephen A.; Page, Ralph H.; Ebbers, Christopher A.; Beach, Raymond J.

2004-03-09

A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

Daylight operation of a sodium laser guide star

NASA Astrophysics Data System (ADS)

Hart, Michael; Jefferies, Stuart; Murphy, Neil

2016-07-01

We report photometric measurements of a sodium resonance guide star against the daylight sky when observed through a tuned magneto-optical filter (MOF). The MOF comprises a sodium vapor cell in a kilogauss-level magnetic field between crossed polarizers and has a very narrow transmission profile at the sodium D2 resonance of approximately 0.008 nm. Our observations were made with the 1.5 m Kuiper telescope on Mt. Bigelow, AZ, which has a separately mounted guide star laser projecting a circularly polarized single-frequency beam of approximately 6.5 W at 589.16 nm. Both the beam projector and the 1.5 m telescope were pointed close to zenith; the baseline between them is approximately 5 m. Measurements of the guide star were made on the morning of 2016 March 24 using an imaging camera focused on the beacon and looking through the full aperture of the telescope. The guide star flux was estimated at 1.20×106 photon/m2/s while at approximately 45 minutes after sunrise, the sky background through the MOF was 1100 photon/m2/s/arcsec2. We interpret our results in terms of thermal infrared observations with adaptive optics on the next generation of extremely large telescopes now being built.

Development and implementation of the guiding stars nutrition guidance program.

PubMed

Fischer, Leslie M; Sutherland, Lisa A; Kaley, Lori A; Fox, Tracy A; Hasler, Clare M; Nobel, Jeremy; Kantor, Mark A; Blumberg, Jeffrey

2011-01-01

PURPOSE . To describe the collaborative process between a grocery retailer and a panel of nutrition experts used to develop a nutrition guidance system (Guiding Stars) that evaluates the nutrient profile of all edible products in the supermarket, and to report the results of the food and beverage ratings. DESIGN . A collaboration between a private retailer and members of the scientific community that led to the development of a scoring algorithm used to evaluate the nutritional quality of foods and beverages. SETTING/SUBJECTS . Northeast supermarkets (n  =  160). MEASURES . Food and beverage nutrition ratings and distribution of stars across different grocery categories. ANALYSIS . Descriptive statistics for rating distributions were computed. T-tests were conducted to assess differences in mean nutrient values between foods with zero versus three stars or a dichotomized variable representing all foods with one to three stars. RESULTS . All edible grocery items (n  =  27,466) were evaluated, with 23.6% earning at least one star. Items receiving at least one star had lower mean levels of sodium, saturated fat, and sugars and higher amounts of fiber than products not earning stars. CONCLUSION . The Guiding Stars system rates edible products without regard to brand or manufacturer, and provides consumers with a simple tool to quickly identify more nutritious choices while shopping. The low percentage of products qualifying for stars reflects poorly on the food choices available to Americans.

CBT Pilot Program Instructional Guide. Basic Drafting Skills Curriculum Delivered through CAD Workstations and Artificial Intelligence Software.

ERIC Educational Resources Information Center

Smith, Richard J.; Sauer, Mardelle A.

This guide is intended to assist teachers in using computer-aided design (CAD) workstations and artificial intelligence software to teach basic drafting skills. The guide outlines a 7-unit shell program that may also be used as a generic authoring system capable of supporting computer-based training (CBT) in other subject areas. The first section…

Hybrid Applications Of Artificial Intelligence

NASA Technical Reports Server (NTRS)

Borchardt, Gary C.

1988-01-01

STAR, Simple Tool for Automated Reasoning, is interactive, interpreted programming language for development and operation of artificial-intelligence application systems. Couples symbolic processing with compiled-language functions and data structures. Written in C language and currently available in UNIX version (NPO-16832), and VMS version (NPO-16965).

Visible near-diffraction-limited lucky imaging with full-sky laser-assisted adaptive optics

NASA Astrophysics Data System (ADS)

Basden, A. G.

2014-08-01

Both lucky imaging techniques and adaptive optics require natural guide stars, limiting sky-coverage, even when laser guide stars are used. Lucky imaging techniques become less successful on larger telescopes unless adaptive optics is used, as the fraction of images obtained with well-behaved turbulence across the whole telescope pupil becomes vanishingly small. Here, we introduce a technique combining lucky imaging techniques with tomographic laser guide star adaptive optics systems on large telescopes. This technique does not require any natural guide star for the adaptive optics, and hence offers full sky-coverage adaptive optics correction. In addition, we introduce a new method for lucky image selection based on residual wavefront phase measurements from the adaptive optics wavefront sensors. We perform Monte Carlo modelling of this technique, and demonstrate I-band Strehl ratios of up to 35 per cent in 0.7 arcsec mean seeing conditions with 0.5 m deformable mirror pitch and full adaptive optics sky-coverage. We show that this technique is suitable for use with lucky imaging reference stars as faint as magnitude 18, and fainter if more advanced image selection and centring techniques are used.

Recent Science and Engineering Results with the Laser Guidestar Adaptive Optics System at Lick Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gavel, D T; Gates, E; Max, C

2002-10-17

The Lick Observatory laser guide star adaptive optics system has undergone continual improvement and testing as it is being integrated as a facility science instrument on the Shane 3 meter telescope. Both Natural Guide Star (NGS) and Laser Guide Star (LGS) modes are now used in science observing programs. We report on system performance results as derived from data taken on both science and engineering nights and also describe the newly developed on-line techniques for seeing and system performance characterization. We also describe the future enhancements to the Lick system that will enable additional science goals such as long-exposure spectroscopy.

Design of an infrared camera based aircraft detection system for laser guide star installations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedman, H.; Macintosh, B.

1996-03-05

There have been incidents in which the irradiance resulting from laser guide stars have temporarily blinded pilots or passengers of aircraft. An aircraft detection system based on passive near infrared cameras (instead of active radar) is described in this report.

Laser Guidestar Satellite for Ground-based Adaptive Optics Imaging of Geosynchronous Satellites and Astronomical Targets

NASA Astrophysics Data System (ADS)

Marlow, W. A.; Cahoy, K.; Males, J.; Carlton, A.; Yoon, H.

2015-12-01

Real-time observation and monitoring of geostationary (GEO) satellites with ground-based imaging systems would be an attractive alternative to fielding high cost, long lead, space-based imagers, but ground-based observations are inherently limited by atmospheric turbulence. Adaptive optics (AO) systems are used to help ground telescopes achieve diffraction-limited seeing. AO systems have historically relied on the use of bright natural guide stars or laser guide stars projected on a layer of the upper atmosphere by ground laser systems. There are several challenges with this approach such as the sidereal motion of GEO objects relative to natural guide stars and limitations of ground-based laser guide stars; they cannot be used to correct tip-tilt, they are not point sources, and have finite angular sizes when detected at the receiver. There is a difference between the wavefront error measured using the guide star compared with the target due to cone effect, which also makes it difficult to use a distributed aperture system with a larger baseline to improve resolution. Inspired by previous concepts proposed by A.H. Greenaway, we present using a space-based laser guide starprojected from a satellite orbiting the Earth. We show that a nanosatellite-based guide star system meets the needs for imaging GEO objects using a low power laser even from 36,000 km altitude. Satellite guide star (SGS) systemswould be well above atmospheric turbulence and could provide a small angular size reference source. CubeSatsoffer inexpensive, frequent access to space at a fraction of the cost of traditional systems, and are now being deployed to geostationary orbits and on interplanetary trajectories. The fundamental CubeSat bus unit of 10 cm cubed can be combined in multiple units and offers a common form factor allowing for easy integration as secondary payloads on traditional launches and rapid testing of new technologies on-orbit. We describe a 6U CubeSat SGS measuring 10 cm x 20 cm x 30 cm with laser power on the order of milliwatts, and a commercial off the shelf based attitude determination and control system, among others. Different from standard 1U and 3U buses, the 6U form factor allows for a propulsion system for navigating around multiple targets in the GEO belt.

System for star catalog equalization to enhance attitude determination

NASA Technical Reports Server (NTRS)

Liu, Yong (Inventor); Wu, Yeong-Wei Andy (Inventor); Li, Rongsheng (Inventor)

2001-01-01

An apparatus for star catalog equalization to enhance attitude determination includes a star tracker, a star catalog and a controller. The star tracker is used to sense the positions of stars and generate signals corresponding to the positions of the stars as seen in its field of view. The star catalog contains star location data that is stored using a primary and multiple secondary arrays sorted by both declination (DEC) and right ascension (RA), respectively. The star location data stored in the star catalog is predetermined by calculating a plurality of desired star locations, associating one of a plurality of stars with each of the plurality of desired star locations based upon a neighborhood association angle to generate an associated plurality of star locations: If an artificial star gap occurs during association, then the neighborhood association angle for reassociation is increased. The controller uses the star catalog to determine which stars to select to provide star measurement residuals for correcting gyroscope bias and spacecraft attitude.

Numerical simulations of downward convective overshooting in giants

NASA Astrophysics Data System (ADS)

Tian, Chun-Lin; Deng, Li-Cai; Chan, Kwing-Lam

2009-09-01

An attempt at understanding downward overshooting in the convective envelopes of post-main-sequence stars has been made on the basis of three-dimensional large-eddy simulations, using artificially modified OPAL opacity and taking into account radiation and ionization in the equation of state. Two types of star, an intermediate-mass star and a massive star, were considered. To avoid a long thermal relaxation time of the intermediate-mass star, we increased the stellar energy flux artificially while trying to maintain a structure close to the one given by a 1D stellar model. A parametric study of the flux factor was performed. For the massive star, no such process was necessary. Numerical results were analysed when the system reached the statistical steady state. It was shown that the penetration distance in pressure scaleheights is of the order of unity. The scaling relations between penetration distance, input flux and vertical velocity fluctuations studied by Singh et al. were checked. The anisotropy of the turbulent convection and the diffusion models of the third-order moments representing the non-local transport were also investigated. These models are dramatically affected by the velocity fields and no universal constant parameters seem to exist. The limitations of the numerical results were also discussed.

The Optical Gravitational Lensing Experiment. Eclipsing Binary Stars in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Wyrzykowski, L.; Udalski, A.; Kubiak, M.; Szymanski, M. K.; Zebrun, K.; Soszynski, I.; Wozniak, P. R.; Pietrzynski, G.; Szewczyk, O.

2004-03-01

We present new version of the OGLE-II catalog of eclipsing binary stars detected in the Small Magellanic Cloud, based on Difference Image Analysis catalog of variable stars in the Magellanic Clouds containing data collected from 1997 to 2000. We found 1351 eclipsing binary stars in the central 2.4 square degree area of the SMC. 455 stars are newly discovered objects, not found in the previous release of the catalog. The eclipsing objects were selected with the automatic search algorithm based on the artificial neural network. The full catalog is accessible from the OGLE Internet archive.

Star Ware: The Amateur Astronomer's Guide to Choosing, Buying, and Using Telescopes and Accessories, 3rd Edition

NASA Astrophysics Data System (ADS)

Harrington, Philip S.

2002-05-01

Praise for the Second Edition of Star Ware "Star Ware is still a tour de force that any experienced amateur will find invaluable, and which hardware-minded beginners will thoroughly enjoy." -Robert Burnham, Sky & Telescope magazine "Star Ware condenses between two covers what would normally take a telescope buyer many months to accumulate." -John Shibley, Astronomy magazine Now more than ever, the backyard astronomer has a dazzling array of choices when it comes to telescope shopping-which can make choosing just the right sky-watching equipment a formidable challenge. In this revised and updated edition of Star Ware, the essential guide to buying astronomical equipment, award-winning astronomy writer Philip Harrington does the work for you, analyzing and exploring today's astronomy market and offering point-by-point comparisons of everything you need. Whether you're an experienced amateur astronomer or just getting started, Star Ware, Third Edition will prepare you to explore the farthest reaches of space with: Extensive, expanded reviews of leading models and accessories, including dozens of new products, to help you buy smart

STAR - A computer language for hybrid AI applications

NASA Technical Reports Server (NTRS)

Borchardt, G. C.

1986-01-01

Constructing Artificial Intelligence application systems which rely on both symbolic and non-symbolic processing places heavy demands on the communication of data between dissimilar languages. This paper describes STAR (Simple Tool for Automated Reasoning), a computer language for the development of AI application systems which supports the transfer of data structures between a symbolic level and a non-symbolic level defined in languages such as FORTRAN, C and PASCAL. The organization of STAR is presented, followed by the description of an application involving STAR in the interpretation of airborne imaging spectrometer data.

Book Review: Stars (Copyright 1985, Golden Press; New York)

NASA Astrophysics Data System (ADS)

Marigza, R. N., Jr.

2009-06-01

Stars is a part of the Golden Guides collection produced by Golden Press. It is a small 160 page paperback guide to the constellations, the sun, the moon, planets, and other celestial bodies. The book is convenient to carry along wherever you go, making it an easy to access reference material.

Consumers' Response to an On-Shelf Nutrition Labelling System in Supermarkets: Evidence to Inform Policy and Practice.

PubMed

Hobin, Erin; Bollinger, Bryan; Sacco, Jocelyn; Liebman, Eli; Vanderlee, Lana; Zuo, Fei; Rosella, Laura; L'abbe, Mary; Manson, Heather; Hammond, David

2017-09-01

Policy Points: On-shelf nutrition labelling systems in supermarkets, such as the Guiding Stars system, are intended to provide consumers with simple, standardized nutrition information to support more informed and healthier food choices. Policies that support the provision of simplified nutrition labelling systems may encourage consumers to make positive shifts in food-purchasing behaviors. The shifts in consumer food-purchasing patterns observed in our study after the introduction of the Guiding Stars system in supermarkets translated into measurable nutritional benefits, including more items purchased with slightly less trans fat and sugar and more fiber and omega-3 fatty acids. This study is one of the first to report the positive impact of an on-shelf nutrition labelling system on supermarket sales and revenues-key information that was specifically requested by the US National Academies, as such labelling interventions may be more sustainable if they lead to higher revenues. Providing a nutrition rating system on the front of food packages or on retail shelf tags has been proposed as a policy strategy for supporting healthier food choices. Guiding Stars is an on-shelf nutrition labelling system that scores foods in a supermarket based on nutritional quality; scores are then translated into ratings of 0 to 3 stars. It is consistent with evidence-informed recommendations for well-designed labels, except for not labelling 0-star products. The largest supermarket retailer in Canada rolled out the Guiding Stars system in supermarkets across Ontario, Canada. The aim of our study was to examine the extent to which consumers respond to an on-shelf nutrition labelling system in supermarkets to inform current and future nutrition labelling policies and practices. Capitalizing on a natural experiment, we conducted a quasi-experimental study across 3 supermarket banners (or "chains") in Ontario, one of which implemented the Guiding Stars system in 2012. We used aggregated supermarket transaction data to test the effect of Guiding Stars on the nutritional quality of food purchases in intervention supermarkets relative to control supermarkets. We also conducted exit surveys among 783 randomly selected shoppers from intervention and control supermarkets to assess consumer awareness, understanding, trust, and self-reported use of the labelling system. Relative to control supermarkets, shoppers in intervention supermarkets made small but significant shifts toward purchasing foods with higher nutritional ratings; however, shifts varied in direction and magnitude across food categories. These shifts translated into foods being purchased with slightly less trans fat and sugar and more fiber and omega-3 fatty acids. We also found increases in the number of products per transaction, price per product purchased, and total revenues. Results of the exit surveys indicate a modest proportion of consumers were aware of, understood, and trusted Guiding Stars in intervention supermarkets, and a small proportion of consumers reported using this system when making purchasing decisions. However, 47% of shoppers exposed to Guiding Stars were confused when asked to interpret the meaning of a 0-star product that does not display a rating on the shelf tag. This study demonstrates support for policies promoting on-shelf nutrition labels designed according to evidence-informed principles, but policymakers should move forward with caution when investing in such systems until research has confirmed optimal label design, clarified the mechanisms through which dietary intake is improved, and assessed associations with nutrition-related health outcomes. © 2017 Milbank Memorial Fund.

CCD centroiding experiment for JASMINE and ILOM

NASA Astrophysics Data System (ADS)

Yano, Taihei; Araki, Hiroshi; Gouda, Naoteru; Kobayashi, Yukiyasu; Tsujimoto, Takuji; Nakajima, Tadashi; Kawano, Nobuyuki; Tazawa, Seiichi; Yamada, Yoshiyuki; Hanada, Hideo; Asari, Kazuyoshi; Tsuruta, Seiitsu

2006-06-01

JASMINE and ILOM are space missions which are in progress at the National Astronomical Observatory of Japan. These two projects need a common astrometric technique to obtain precise positions of star images on solid state detectors to accomplish the objectives. We have carried out measurements of centroid of artificial star images on a CCD to investigate the accuracy of the positions of the stars, using an algorithm for estimating them from photon weighted means of the stars. We find that the accuracy of the star positions reaches 1/300 pixel for one measurement. We also measure positions of stars, using an algorithm for correcting the distorted optical image. Finally, we find that the accuracy of the measurement for the positions of the stars from the strongly distorted image is under 1/150 pixel for one measurement.

America's Star Libraries

ERIC Educational Resources Information Center

Lyons, Ray; Lance, Keith Curry

2009-01-01

"Library Journal"'s new national rating of public libraries, the "LJ" Index of Public Library Service, identifies 256 "star" libraries. It rates 7,115 public libraries. The top libraries in each group get five, four, or three Michelin guide-like stars. All included libraries, stars or not, can use their scores to learn from their peers and improve…

Live imaging using adaptive optics with fluorescent protein guide-stars

PubMed Central

Tao, Xiaodong; Crest, Justin; Kotadia, Shaila; Azucena, Oscar; Chen, Diana C.; Sullivan, William; Kubby, Joel

2012-01-01

Spatially and temporally dependent optical aberrations induced by the inhomogeneous refractive index of live samples limit the resolution of live dynamic imaging. We introduce an adaptive optical microscope with a direct wavefront sensing method using a Shack-Hartmann wavefront sensor and fluorescent protein guide-stars for live imaging. The results of imaging Drosophila embryos demonstrate its ability to correct aberrations and achieve near diffraction limited images of medial sections of large Drosophila embryos. GFP-polo labeled centrosomes can be observed clearly after correction but cannot be observed before correction. Four dimensional time lapse images are achieved with the correction of dynamic aberrations. These studies also demonstrate that the GFP-tagged centrosome proteins, Polo and Cnn, serve as excellent biological guide-stars for adaptive optics based microscopy. PMID:22772285

Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars.

PubMed

Marc, Fabien; Guillet de Chatellus, Hugues; Pique, Jean-Paul

2009-03-30

The possibility to produce diffraction-limited images by large telescopes through Adaptive Optics is closely linked to the precision of measurement of the position of the guide star on the wavefront sensor. In the case of laser guide stars, many parameters can lead to a strong distortion on the shape of the LGS spot. Here we study the influence of both the saturation of the sodium layer excited by different types of lasers, the spatial quality of the laser mode at the ground and the influence of the atmospheric turbulence on the upward propagation of the laser beam. Both shape and intensity of the LGS spot are found to depend strongly on these three effects with important consequences on the precision on the wavefront analysis.

Progress with the lick adaptive optics system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gavel, D T; Olivier, S S; Bauman, B

2000-03-01

Progress and results of observations with the Lick Observatory Laser Guide Star Adaptive Optics System are presented. This system is optimized for diffraction-limited imaging in the near infrared, 1-2 micron wavelength bands. We describe our development efforts in a number of component areas including, a redesign of the optical bench layout, the commissioning of a new infrared science camera, and improvements to the software and user interface. There is also an ongoing effort to characterize the system performance with both natural and laser guide stars and to fold this data into a refined system model. Such a model can bemore » used to help plan future observations, for example, predicting the point-spread function as a function of seeing and guide star magnitude.« less

Improving sodium laser guide star brightness by polarization switching

PubMed Central

Fan, Tingwei; Zhou, Tianhua; Feng, Yan

2016-01-01

Optical pumping with circularly polarized light has been used to enhance the brightness of sodium laser guide star. But the benefit is reduced substantially due to the precession of sodium atoms in geomagnetic field. Switching the laser between left and right circular polarization at the Larmor frequency is proposed to improve the return. With ESO’s laser guide star system at Paranal as example, numerical simulation shows that the return flux is increased when the angle between geomagnetic field and laser beam is larger than 60°, as much as 50% at 90°. The proposal is significant since most astronomical observation is at angle between 60° and 90° and it only requires a minor addition to the delivery optics of present laser system. PMID:26797503

On-sky performance of the tip-tilt correction system for GLAS using an EMCCD camera

NASA Astrophysics Data System (ADS)

Skvarč, Jure; Tulloch, Simon

2008-07-01

Adaptive optics systems based on laser guide stars still need a natural guide star (NGS) to correct for the image motion caused by the atmosphere and by imperfect telescope tracking. The ability to properly compensate for this motion using a faint NGS is critical to achieve large sky coverage. For the laser guide system (GLAS) on the 4.2 m William Herschel Telescope we designed and tested in the laboratory and on-sky a tip-tilt correction system based on a PC running Linux and an EMCCD technology camera. The control software allows selection of different centroiding algorithms and loop control methods as well as the control parameters. Parameter analysis has been performed using tip-tilt only correction before the laser commissioning and the selected sets of parameters were then used during commissioning of the laser guide star system. We have established the SNR of the guide star as a function of magnitude, depending on the image sampling frequency and on the dichroic used in the optical system; achieving a measurable improvement using full AO correction with NGSes down to magnitude range R=16.5 to R=18. A minimum SNR of about 10 was established to be necessary for a useful correction. The system was used to produce 0.16 arcsecond images in H band using bright NGS and laser correction during GLAS commissioning runs.

Femtosecond Amplifiers and Microlasers in the Deep Ultraviolet

DTIC Science & Technology

2013-11-19

Laser guide stars have applications of growing importance to the DOD, astronomy, and environmental monitoring. However, realizing a laser that is...pump wavelength, photoassociation-pumped lasers hold considerable promise as guide star lasers . The most exciting aspect of these results, however...highlights of several experiments that were mentioned briefly in the last section. A. Dual Wavelength Sodium Laser Pumped By Na-Xe Pair Absorption

Artificial intelligence guides system's best practices, cutting costs and improving services.

PubMed

1999-06-01

One for the history books. Clinical care improvement initiatives guided by a sophisticated artificial intelligence program have helped a major Virginia integrated health system make dramatic improvements in the cost and quality of its health care services. Find out how the technological innovation has earned Sentara Health System a place in the permanent collection of the Smithsonian's National Museum of American History.

[The necessity of artificial kidney seeper in the ultrasonography-guided percutaneous nephrolithotomy: a randomized controlled study].

PubMed

Ye, J J; Yang, Y; Zhang, H J; Zheng, Y C; Pan, Y; Xie, H

2018-05-01

Objective: To investigate the necessity of artificial kidney seeper which made through inserting a ureteral tube in the ureter to the ultrasonography-guided percutaneous nephrolithotomy (PCNL). Methods: This was a randomized prospective study. Patients who conformed to the inclusion and exclusion criteria were enrolled at Department of Urology, Frist Affiliated Hospital of Wenzhou Medical University from January 2016 to May 2017. Totally 291 patients were included in the study. Patients were randomly assigned into two groups (artificial kidney seeper group and non-artificial kidney seeper group) in different kidney seeper level (5 to <10 mm, 10 to 20 mm) respectively. The artificial kidney seeper group was inserted by a ureteral cathedral, then were underwent the ultrasonography-guided PCNL in prone position. The non-artificial kidney seeper group were underwent the ultrasonography-guided PCNL in prone position directly. The t test, χ(2) test, repeated measure analysis was used to data measurement, respectively. Results: Four patients who diagnosed pyonephrosis were excluded. On the 5 to <10 mm level, fever rate (14.6% vs . 4.8%, χ(2)=5.07, P =0.03), operation time ((65.7±9.9)min vs . (50.3±7.4)min, t =11.47, P =0.00), cost ((18 327±903) yuan vs . (14 583±784) yuan, t =24.50, P =0.00) about artificial kidney seeper group and non-artificial kidney seeper group had statistical differences. And on the 10 to 20 mm level, fever rate (14.5% vs . 3.39%, χ(2)=4.53, P =0.03), operation time ((66.0±9.9)min vs . (52.4±8.9)min, t =8.30, P =0.00), cost ((16 548±537) yuan vs. (13 102±629) yuan, t =32.10, P =0.00) about artificial kidney seeper group and non-artificial kidney seeper group had statistical differences. And there were no statistical differences in the success rate of puncturing, the failures of the treatment to the stone pieces falling into the ureter and clearance rate of the stone and so on. In this study, 2 cases recovered after received transfusion and digital subtraction angiography artery embolization treatments; D-J tube was indwelled into 4 cases guiding by super smooth thread; 4 cases were finished the surgeries with the help of ureteroscopy, because the stone pieces fell into the ureter during the surgeries. And there was no patients developing septic shock, adjacent viscera injury or other serious complications. Conclusion: For seasoned doctors, there is no necessity of regularly artificial kidney seeper for PCNL when the pre-operation seeper ranging from 5 to 20 mm.

Series production of next-generation guide-star lasers at TOPTICA and MPBC

NASA Astrophysics Data System (ADS)

Enderlein, Martin; Friedenauer, Axel; Schwerdt, Robin; Rehme, Paul; Wei, Daoping; Karpov, Vladimir; Ernstberger, Bernhard; Leisching, Patrick; Clements, Wallace R. L.; Kaenders, Wilhelm G.

2014-07-01

Large telescopes equipped with adaptive optics require high power 589-nm continuous-wave sources with emission linewidths of ~5 MHz. These guide-star lasers should be highly reliable and simple to operate and maintain for many years at the top of a mountain facility. After delivery of the first 20-W systems to our lead customer ESO, TOPTICA and MPBC have begun series production of next-generation sodium guide-star lasers. The chosen approach is based on ESO's patented narrow-band Raman fiber amplifier (RFA) technology [1]. A master oscillator signal from a TOPTICA 50-mW, 1178-nm diode laser, with stabilized emission frequency and linewidth of ~ 1 MHz, is amplified in an MPBC polarization-maintaining (PM) RFA pumped by a high-power 1120-nm PM fiber laser. With efficient stimulated Brillouin scattering suppression, an unprecedented 40 W of narrow-band RFA output has been obtained. This is spatially mode-matched into a patented resonant-cavity frequency doubler providing also the repumper light [2]. With a diffraction-limited output beam and doubling efficiencies < 80%, all ESO design goals have been easily fulfilled. Together with a wall-plug efficiency of < 3%, including all system controls, and a cooling liquid flow of only 5 l/min, the modular, turn-key, maintenance-free and compact system design allows a direct integration with a launch telescope. With these fiber-based guide star lasers, TOPTICA for the first time offers a fully engineered, off-the-shelf guide star laser system for ground-based optical telescopes. Here we present a comparison of test results of the first batch of laser systems, demonstrating the reproducibility of excellent optical characteristics.

Smart tissue anastomosis robot (STAR): a vision-guided robotics system for laparoscopic suturing.

PubMed

Leonard, Simon; Wu, Kyle L; Kim, Yonjae; Krieger, Axel; Kim, Peter C W

2014-04-01

This paper introduces the smart tissue anastomosis robot (STAR). Currently, the STAR is a proof-of-concept for a vision-guided robotic system featuring an actuated laparoscopic suturing tool capable of executing running sutures from image-based commands. The STAR tool is designed around a commercially available laparoscopic suturing tool that is attached to a custom-made motor stage and the STAR supervisory control architecture that enables a surgeon to select and track incisions and the placement of stitches. The STAR supervisory-control interface provides two modes: A manual mode that enables a surgeon to specify the placement of each stitch and an automatic mode that automatically computes equally-spaced stitches based on an incision contour. Our experiments on planar phantoms demonstrate that the STAR in either mode is more accurate, up to four times more consistent and five times faster than surgeons using state-of-the-art robotic surgical system, four times faster than surgeons using manual Endo360(°)®, and nine times faster than surgeons using manual laparoscopic tools.

A Randomized Controlled Trial Evaluating the See, Tilt, Align, and Rotate (STAR) Maneuver on Skill Acquisition for Simulated Ultrasound-Guided Interventional Procedures.

PubMed

Lam, Nicholas C K; Fishburn, Steven J; Hammer, Angie R; Petersen, Timothy R; Gerstein, Neal S; Mariano, Edward R

2015-06-01

Achieving the best view of the needle and target anatomy when performing ultrasound-guided interventional procedures requires technical skill, which novices may find difficult to learn. We hypothesized that teaching novice performers to use 4 sequential steps (see, tilt, align, and rotate [STAR] method) to identify the needle under ultrasound guidance is more efficient than training with the commonly described probe movements of align, rotate, and tilt (ART). This study compared 2 instructional methods for transducer manipulation including alignment of a probe and needle by novices during a simulated ultrasound-guided nerve block. Right-handed volunteers between the ages of 18 and 55 years who had no previous ultrasound experience were recruited and randomized to 1 of 2 groups; one group was trained to troubleshoot misalignment with the ART method, and the other was trained with the new STAR maneuver. Participants performed the task, consisting of directing a needle in plane to 3 targets in a standardized gelatin phantom 3 times. The performance assessor and data analyst were blinded to group assignment. Thirty-five participants were recruited. The STAR group was able to complete the task more quickly (P < .001) and visualized the needle in a greater proportion of the procedure time (P = .004) compared to the ART group. All STAR participants were able to complete the task, whereas 41% of ART participants abandoned the task (P = .003). Novices are able to complete a simulated ultrasound-guided nerve block more quickly and efficiently when trained with the 4-step STAR maneuver compared to the ART method. © 2015 by the American Institute of Ultrasound in Medicine.

The Polychromatic Laser Guide Star for tilt measurement: progress report of the demonstrator at Observatoire de Haute Provence

NASA Astrophysics Data System (ADS)

Foy, Renaud; Éric, Pierre; Eysseric, Jérôme; Foy, Françoise; Fusco, Thierry; Girard, Julien; Le Van Suu, Auguste; Perruchot, Sandrine; Richaud, Pierre; Richaud, Yoann; Rondeau, Xavier; Tallon, Michel; Thiébaut, Éric; Boër, Michel

2007-09-01

The Polychromatic Laser Guide Star aims at providing for the tilt measurement from a LGS without any natural guide star. Thus it allows adaptive optics to provide us with a full sky coverage. This is critical in particular to extend adaptive optics to the visible range, where isoplanatism is so small that the probability is negligible to find a natural star to measure the tilt. We report new results obtained within the framework of the Polychromatic LGS programme ELP-OA. Natural stars have been used to mimic the PLGS, in order to check the feasibility of using the difference in the tilt at two wavelengths to derive the tilt itself. We report results from the ATTILA experiment obtained at the 1.52 m telescope at Observatoire de Haute-Provence. Tilts derived from the differential tilts are compared with direct tilt measurements. The accuracy of the measurements is currently ~ 1.5 Airy disk rms at 550 nm. These results prove the feasibility of the Polychromatic Laser Guide Star programme ELP-OA. New algorithms based on inverse problems under development within our programme would lead to smaller error bars by 1 magnitude, as soon as they will run fast enough. We describe the ELP-OA demonstrator which we are setting up at the same telescope, with a special emphasis on the optimization of the excitation process, which definitely has to rely on the two-photon excitation of sodium atoms in the mesosphere. We will describe the implementation at the telescope, including the projector device, the focal instrumentation and the NdYAG pumped dye lasers.

Interactive Astronomy.

ERIC Educational Resources Information Center

Martin, Jean K.

1997-01-01

Presents guiding principles for developing interactive lessons for the World Wide Web. Describes "Amazing Space: Education Online from the Hubble Space Telescope", a program where students study spectacular Hubble Space Telescope images of stars and star-forming regions to learn about the life cycle of stars and the creation of atoms. (JRH)

STAR- A SIMPLE TOOL FOR AUTOMATED REASONING SUPPORTING HYBRID APPLICATIONS OF ARTIFICIAL INTELLIGENCE (DEC VAX VERSION)

NASA Technical Reports Server (NTRS)

Borchardt, G. C.

1994-01-01

The Simple Tool for Automated Reasoning program (STAR) is an interactive, interpreted programming language for the development and operation of artificial intelligence (AI) application systems. STAR provides an environment for integrating traditional AI symbolic processing with functions and data structures defined in compiled languages such as C, FORTRAN and PASCAL. This type of integration occurs in a number of AI applications including interpretation of numerical sensor data, construction of intelligent user interfaces to existing compiled software packages, and coupling AI techniques with numerical simulation techniques and control systems software. The STAR language was created as part of an AI project for the evaluation of imaging spectrometer data at NASA's Jet Propulsion Laboratory. Programming in STAR is similar to other symbolic processing languages such as LISP and CLIP. STAR includes seven primitive data types and associated operations for the manipulation of these structures. A semantic network is used to organize data in STAR, with capabilities for inheritance of values and generation of side effects. The AI knowledge base of STAR can be a simple repository of records or it can be a highly interdependent association of implicit and explicit components. The symbolic processing environment of STAR may be extended by linking the interpreter with functions defined in conventional compiled languages. These external routines interact with STAR through function calls in either direction, and through the exchange of references to data structures. The hybrid knowledge base may thus be accessed and processed in general by either side of the application. STAR is initially used to link externally compiled routines and data structures. It is then invoked to interpret the STAR rules and symbolic structures. In a typical interactive session, the user enters an expression to be evaluated, STAR parses the input, evaluates the expression, performs any file input/output required, and displays the results. The STAR interpreter is written in the C language for interactive execution. It has been implemented on a VAX 11/780 computer operating under VMS, and the UNIX version has been implemented on a Sun Microsystems 2/170 workstation. STAR has a memory requirement of approximately 200K of 8 bit bytes, excluding externally compiled functions and application-dependent symbolic definitions. This program was developed in 1985.

STAR- A SIMPLE TOOL FOR AUTOMATED REASONING SUPPORTING HYBRID APPLICATIONS OF ARTIFICIAL INTELLIGENCE (UNIX VERSION)

NASA Technical Reports Server (NTRS)

Borchardt, G. C.

1994-01-01

The Simple Tool for Automated Reasoning program (STAR) is an interactive, interpreted programming language for the development and operation of artificial intelligence (AI) application systems. STAR provides an environment for integrating traditional AI symbolic processing with functions and data structures defined in compiled languages such as C, FORTRAN and PASCAL. This type of integration occurs in a number of AI applications including interpretation of numerical sensor data, construction of intelligent user interfaces to existing compiled software packages, and coupling AI techniques with numerical simulation techniques and control systems software. The STAR language was created as part of an AI project for the evaluation of imaging spectrometer data at NASA's Jet Propulsion Laboratory. Programming in STAR is similar to other symbolic processing languages such as LISP and CLIP. STAR includes seven primitive data types and associated operations for the manipulation of these structures. A semantic network is used to organize data in STAR, with capabilities for inheritance of values and generation of side effects. The AI knowledge base of STAR can be a simple repository of records or it can be a highly interdependent association of implicit and explicit components. The symbolic processing environment of STAR may be extended by linking the interpreter with functions defined in conventional compiled languages. These external routines interact with STAR through function calls in either direction, and through the exchange of references to data structures. The hybrid knowledge base may thus be accessed and processed in general by either side of the application. STAR is initially used to link externally compiled routines and data structures. It is then invoked to interpret the STAR rules and symbolic structures. In a typical interactive session, the user enters an expression to be evaluated, STAR parses the input, evaluates the expression, performs any file input/output required, and displays the results. The STAR interpreter is written in the C language for interactive execution. It has been implemented on a VAX 11/780 computer operating under VMS, and the UNIX version has been implemented on a Sun Microsystems 2/170 workstation. STAR has a memory requirement of approximately 200K of 8 bit bytes, excluding externally compiled functions and application-dependent symbolic definitions. This program was developed in 1985.

A novel double fine guide sensor design on space telescope

NASA Astrophysics Data System (ADS)

Zhang, Xu-xu; Yin, Da-yi

2018-02-01

To get high precision attitude for space telescope, a double marginal FOV (field of view) FGS (Fine Guide Sensor) is proposed. It is composed of two large area APS CMOS sensors and both share the same lens in main light of sight. More star vectors can be get by two FGS and be used for high precision attitude determination. To improve star identification speed, the vector cross product in inter-star angles for small marginal FOV different from traditional way is elaborated and parallel processing method is applied to pyramid algorithm. The star vectors from two sensors are then used to attitude fusion with traditional QUEST algorithm. The simulation results show that the system can get high accuracy three axis attitudes and the scheme is feasibility.

Stellar Ideas: Exploring Students' Understanding of Stars

ERIC Educational Resources Information Center

Agan, Lori

2004-01-01

In this study, high school and first-year undergraduate students were asked about their understanding of stars. The hypothesis guiding this research posits that high school students who have taken a semester-long astronomy course will have an understanding of stars most related to scientific knowledge, compared with high school students enrolled…

A search for artificial signals from the newly discovered planetary systems

NASA Astrophysics Data System (ADS)

Biraud, Francois; Heidmann, Jean; Tarter, Jill C.; Airieau, Sabine

1997-01-01

We conducted a search for narrowband artificial signals from the regions of stars around which planetary companions have been recently found: 51 Pegasi, Gliese 229, 70 Virginis, and 47 Ursae Majoris. We used the large Nangay decimetric telescope, with a frequency resolution of 50 Hz, and we scanned over 0.64 and 2.24 MHz respectively around the hydrogen and hydroxyl lines.

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Dam, M A; Mignant, D L; Macintosh, B A

In this paper, the adaptive optics (AO) system at the W.M. Keck Observatory is characterized. The authors calculate the error budget of the Keck AO system operating in natural guide star mode with a near infrared imaging camera. By modeling the control loops and recording residual centroids, the measurement noise and band-width errors are obtained. The error budget is consistent with the images obtained. Results of sky performance tests are presented: the AO system is shown to deliver images with average Strehl ratios of up to 0.37 at 1.58 {micro}m using a bright guide star and 0.19 for a magnitudemore » 12 star.« less

Lick sodium laser guide star: performance during the 1998 LGS observing campaign

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauman, B; Friedman, H; Gavel, D T

1999-07-19

The performance of a sodium laser guide star adaptive optics system depends crucially on the characteristics of the laser guide star in the sodium layer. System performance is quite sensitive to sodium layer spot radiance, that is, return per unit sterradian on the sky, hence we have been working to improve projected beam quality via improvements to the laser and changes to the launched beam format. The laser amplifier was reconfigured to a ''bounce-beam'' geometry, which considerably improves wavefront quality and allows a larger round instead of square launch beam aperture. The smaller beacon makes it easier to block themore » unwanted Rayleigh light and improves the accuracy of Hartmann sensor wavefront measurements in the A0 system. We present measurements of the beam quality and of the resulting sodium beacon and compare to similar measurements from last year.« less

Optimal reconstruction for closed-loop ground-layer adaptive optics with elongated spots.

PubMed

Béchet, Clémentine; Tallon, Michel; Tallon-Bosc, Isabelle; Thiébaut, Éric; Le Louarn, Miska; Clare, Richard M

2010-11-01

The design of the laser-guide-star-based adaptive optics (AO) systems for the Extremely Large Telescopes requires careful study of the issue of elongated spots produced on Shack-Hartmann wavefront sensors. The importance of a correct modeling of the nonuniformity and correlations of the noise induced by this elongation has already been demonstrated for wavefront reconstruction. We report here on the first (to our knowledge) end-to-end simulations of closed-loop ground-layer AO with laser guide stars with such an improved noise model. The results are compared with the level of performance predicted by a classical noise model for the reconstruction. The performance is studied in terms of ensquared energy and confirms that, thanks to the improved noise model, central or side launching of the lasers does not affect the performance with respect to the laser guide stars' flux. These two launching schemes also perform similarly whatever the atmospheric turbulence strength.

National Military Family Association

MedlinePlus

... Action Volunteer Mark Your Calendar Donate Twitter Facebook Instagram Donate Appreciating Military Families: Meet the Wilsons This ... 2017 - National Military Family Association Twitter Facebook Pinterest Instagram Charity Navigator Four Star Charity GuideStar Exchange Better ...

A search for stellar occultations by Uranus, Neptune, Pluto, and their satellites: 1990-1999

NASA Technical Reports Server (NTRS)

Mink, Douglas J.

1991-01-01

A search for occultations of stars by Uranus, Neptune, and Pluto between 1990 and 1999 was carried out by combining ephemeris information and star positions using very accurate occultation modeling software. Stars from both the Space Telescope Guide Catalog and photographic plates taken by Arnold Klemola at Lick Observatory were compared with planet positions from the JPL DE-130 ephemeris, with local modifications for Pluto and Charon. Some 666 possible occultations by the Uranian ring, 143 possible occultations by Neptune, and 40 possible occultations by Pluto and/or Charon were found among stars with visual magnitudes as faint as 16. Before the star positions could be obtained, the occultation prediction software was used to aid many observers in observing the occultation of 28 Sagitarii by Saturn in July 1989. As a test on other outer solar system objects, 17 possible occultations were found in a search of the Guide Star Catalog for occultations by 2060 Chiron, and interesting object between Saturn and Uranus which shows both cometary and asteroidal properties.

A search for stellar occultations by Uranus, Neptune, Pluto, and their satellites: 1990-1999

NASA Astrophysics Data System (ADS)

Mink, Douglas J.

1991-03-01

A search for occultations of stars by Uranus, Neptune, and Pluto between 1990 and 1999 was carried out by combining ephemeris information and star positions using very accurate occultation modeling software. Stars from both the Space Telescope Guide Catalog and photographic plates taken by Arnold Klemola at Lick Observatory were compared with planet positions from the JPL DE-130 ephemeris, with local modifications for Pluto and Charon. Some 666 possible occultations by the Uranian ring, 143 possible occultations by Neptune, and 40 possible occultations by Pluto and/or Charon were found among stars with visual magnitudes as faint as 16. Before the star positions could be obtained, the occultation prediction software was used to aid many observers in observing the occultation of 28 Sagitarii by Saturn in July 1989. As a test on other outer solar system objects, 17 possible occultations were found in a search of the Guide Star Catalog for occultations by 2060 Chiron, and interesting object between Saturn and Uranus which shows both cometary and asteroidal properties.

Laser-sodium interaction for the polychromatic laser guide star project

NASA Astrophysics Data System (ADS)

Bellanger, Veronique; Petit, Alain D.

2002-02-01

We developed a code aimed at determining the laser parameters leading to the maximum return flux of photons at 0.33 micrometers for a polychromatic sodium Laser Guide Star. This software relies upon a full 48-level collisionless and magnetic-field-free density-matrix description of the hyperfine structure of Na and includes Doppler broadening and Zeeman degeneracy. Experimental validation of BEACON was conducted on the SILVA facilities and will also be discussed in this paper.

[Ultrasound-guided microwave ablation with artificial pleural effusion for liver tumor adjacent to 
diaphragmatic dome].

PubMed

Tang, Tian; Gu, Shanzhi; Li, Guowen; Huang, Manping; Huang, Bin; Xiong, Zhengping

2017-02-28

To explore the value of ultrasound-guided microwave ablation with artificial pleural effusion for liver tumor adjacent to diaphragmatic dome.
 Methods: A total of 34 patients with liver tumors located at diaphragmatic dome in Hunan Provincial Tumor Hospital were recruited from January 2014 to October 2015. The number of lesions ≤3 or lesion diameter ≤5 cm was in line with the microwave ablation indications. B ultrasound-guided microwave ablation for the liver tumors was undertaken after the artificial pleural effusion being established. 3-4 weeks later after the microwave ablation, all patients were imaged with enhance CT or MRI. The effect of ablation and the complications were evaluated.
 Results: There were 49 lesions in 34 patients, including 30 cases (88.2%) of complete ablation (CA), 3 cases (8.8%) of partial ablation (PA) and one case with new lesions after ablation (2.9%). Thirty-four patients had (1 580±230.7) mL of pleural effusion volume, while one case had bloody pleural effusion. One case had a diaphragmatic thermal injury, and one case had a biliary tumor infection. All of them showed remission after symptomatic treatment. 
 Conclusion: Combination of ultrasound-guided microwave ablation with artificial pleural effusion is a safe and effective therapy for liver tumor adjacent to diaphragmatic dome.

Performance of the Keck Observatory adaptive-optics system.

PubMed

van Dam, Marcos A; Le Mignant, David; Macintosh, Bruce A

2004-10-10

The adaptive-optics (AO) system at the W. M. Keck Observatory is characterized. We calculate the error budget of the Keck AO system operating in natural guide star mode with a near-infrared imaging camera. The measurement noise and bandwidth errors are obtained by modeling the control loops and recording residual centroids. Results of sky performance tests are presented: The AO system is shown to deliver images with average Strehl ratios of as much as 0.37 at 1.58 microm when a bright guide star is used and of 0.19 for a magnitude 12 star. The images are consistent with the predicted wave-front error based on our error budget estimates.

Adaptive Optics Makes A Research Instrument Out Of A Commercial 30 cm Aperture Telescope

NASA Astrophysics Data System (ADS)

Durig, D. T.

1999-12-01

I recently upgraded my SBIG ST-8 CCD camera with the AO-7 Adaptive Optics unit. This has solved many of the problems with tracking errors and the stability of my telescope mount and allowed me to obtain useful astrometric information on asteroids, comets and supernovae. It is no longer easy to take automated remote images but as long as I am at the observatory, good quality data can be obtained. The AO-7 unit allows me to pick a guide star for the guiding CCD just slightly out of the field of view of the imaging CCD. I am able to guide at the rate of 5 corrections per second with a 13th magnitude guide star. The fastest I have been able to guide is 30 times per second, but there are not usually bright enough stars near the image field to use this rate. When I have to use a dimmer star to guide on, and my rate is as slow as once per two seconds, good results are possible as long as the winds are not too strong. With a focal length of 1775 mm (f/5.75) and 2x2 binning on the CDD I am able to reach at least 18th magnitude objects in a 30 second exposure, but the guiding has to be very good to use these images for astrometry. For objects dimmer than 17th magnitude I normally go to a 2 minute exposure. With this equipment I was the first to observe that a recently discovered object (Comet LINEAR S4) was a comet and not an asteroid as originally reported (see IAUC 7267). I have performed additional astrometric observations on Comets LINEAR S3, S4, T2 and Ferris U1. I have also performed measurements on over a dozen asteroids from the MPC Critical List.

The Optical Gravitational Lensing Experiment. Eclipsing Binary Stars in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Wyrzykowski, L.; Udalski, A.; Kubiak, M.; Szymanski, M.; Zebrun, K.; Soszynski, I.; Wozniak, P. R.; Pietrzynski, G.; Szewczyk, O.

2003-03-01

We present the catalog of 2580 eclipsing binary stars detected in 4.6 square degree area of the central parts of the Large Magellanic Cloud. The photometric data were collected during the second phase of the OGLE microlensing search from 1997 to 2000. The eclipsing objects were selected with the automatic search algorithm based on an artificial neural network. Basic statistics of eclipsing stars are presented. Also, the list of 36 candidates of detached eclipsing binaries for spectroscopic study and for precise LMC distance determination is provided. The full catalog is accessible from the OGLE Internet archive.

Direct wavefront sensing for high-resolution in vivo imaging in scattering tissue

PubMed Central

Wang, Kai; Sun, Wenzhi; Richie, Christopher T.; Harvey, Brandon K.; Betzig, Eric; Ji, Na

2015-01-01

Adaptive optics by direct imaging of the wavefront distortions of a laser-induced guide star has long been used in astronomy, and more recently in microscopy to compensate for aberrations in transparent specimens. Here we extend this approach to tissues that strongly scatter visible light by exploiting the reduced scattering of near-infrared guide stars. The method enables in vivo two-photon morphological and functional imaging down to 700 μm inside the mouse brain. PMID:26073070

CCD centroiding analysis for Nano-JASMINE observation data

NASA Astrophysics Data System (ADS)

Niwa, Yoshito; Yano, Taihei; Araki, Hiroshi; Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki; Tazawa, Seiichi; Hanada, Hideo

2010-07-01

Nano-JASMINE is a very small satellite mission for global space astrometry with milli-arcsecond accuracy, which will be launched in 2011. In this mission, centroids of stars in CCD image frames are estimated with sub-pixel accuracy. In order to realize such a high precision centroiding an algorithm utilizing a least square method is employed. One of the advantages is that centroids can be calculated without explicit assumption of the point spread functions of stars. CCD centroiding experiment has been performed to investigate whether this data analysis is available, and centroids of artificial star images on a CCD are determined with a precision of less than 0.001 pixel. This result indicates parallaxes of stars within 300 pc from Sun can be observed in Nano-JASMINE.

Percutaneous microwave ablation with artificial ascites for symptomatic uterine adenomyosis: initial experience.

PubMed

Hai, Ning; Zhang, Jing; Xu, Ruifang; Han, Zhi-Yu; Liu, Fang Yi

2017-09-01

To evaluate the feasibility, safety and technical efficacy of ultrasound-guided percutaneous microwave ablation with artificial ascites for adenomyosis. Between May 2015 and May 2016, a total of 25 patients with symptomatic adenomyosis who underwent ultrasound-guided percutaneous microwave ablation with artificial ascites were included in this retrospective study. A matching cohort of 50 patients underwent ultrasound-guided percutaneous microwave ablation without artificial ascites as controls. The technical efficacy, complications and short-term treatment effectiveness were assessed and compared with the controls. Artificial ascites was successfully achieved in all of the 25 patients with the administration of a median of 550 mL (range, 250-1200 mL) of solution. There was substantial improvement in achieving a better antenna path in 100% (20/20) of the cases with a poor antenna path. The complete separation was achieved in 23 of 25 patients. The mean ablation time was 26.5 ± 7.3 min and the median non-perfusion volume ratio was 76% which was similar to the control group (p > .05). No serious complications were observed. Patient pain scores for dysmenorrhoea showed a statistically significant decline from the baseline of 6.71 ± 0.96 to 2.92 ± 0.79 and the symptom severity score declined statistically significantly from 21.8 ± 5.5 to 16.4 ± 4.8 at 3 months follow-up. Percutaneous microwave ablation with artificial ascites is feasible, safe and can be effective in improving access for treatment of adenomyosis.

Improved performance of the laser guide star adaptive optics system at Lick Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, J R; Avicola, K; Bauman, B J

1999-07-20

Results of experiments with the laser guide star adaptive optics system on the 3-meter Shane telescope at Lick Observatory have demonstrated a factor of 4 performance improvement over previous results. Stellar images recorded at a wavelength of 2 {micro}m were corrected to over 40% of the theoretical diffraction-limited peak intensity. For the previous two years, this sodium-layer laser guide star system has corrected stellar images at this wavelength to {approx}10% of the theoretical peak intensity limit. After a campaign to improve the beam quality of the laser system, and to improve calibration accuracy and stability of the adaptive optics systemmore » using new techniques for phase retrieval and phase-shifting diffraction interferometry, the system performance has been substantially increased. The next step will be to use the Lick system for astronomical science observations, and to demonstrate this level of performance with the new system being installed on the 10-meter Keck II telescope.« less

Vanguard Preparatory School Observations of the Double Star STF 1692

NASA Astrophysics Data System (ADS)

Anderson, Serenity; Buccola, Breck; Garcia, Karen; Gosney, Matthew; Housatchenko, Jonathan; Martinez, Lilian; Myskow, Wyatt; Renteria, Noah; Schlosser, Ruth; Thompson, Leone; Estrada, Reed; Estrada, Chris

2016-01-01

Using a 22-inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece, students from Vanguard Preparatory observed the binary star Cor Caroli (STF 1692) and found a position angle of 228 degrees as well as an average separation of 21.10". This project was a part of the Vanguard Preparatory Double Star Workshop 2015 in Apple Valley, California.

Star Watch: The Amateur Astronomer's Guide to Finding, Observing, and Learning about Over 125 Celestial Objects

NASA Astrophysics Data System (ADS)

Harrington, Philip S.

2003-07-01

Your Passport to the Universe The night sky is alive with many wonders--distant planets, vast star clusters, glowing nebulae, and expansive galaxies, all waiting to be explored. Let respected astronomy writer Philip Harrington introduce you to the universe in Star Watch, a complete beginner's guide to locating, observing, and understanding these celestial objects. You'll start by identifying the surface features of the Moon, the banded cloud tops of Jupiter, the stunning rings of Saturn, and other members of our solar system. Then you'll venture out beyond our solar system, where you'll learn tips and tricks for finding outstanding deep-sky objects from stars to galaxies, including the entire Messier catalog--a primary goal of every serious beginner. Star Watch features a detailed physical description of each target, including size, distance, and structure, as well as concise directions for locating the objects, handy finder charts, hints on the best times to view each object, and descriptions of what you'll really see through a small telescope or binoculars and with the naked eye. Star Watch will transport you to the farthest depths of space--and return you as a well-traveled, experienced stargazer.

Design constraints of the LST fine guidance sensor

NASA Technical Reports Server (NTRS)

Wissinger, A. B.

1975-01-01

The LST Fine Guidance Sensor design is shaped by the rate of occurrence of suitable guide stars, the competition for telescope focal plane space with the Science Instruments, and the sensitivity of candidate image motion sensors. The relationship between these parameters is presented, and sensitivity to faint stars is shown to be of prime importance. An interferometric technique of image motion sensing is shown to have improved sensitivity and, therefore, a reduced focal plane area requirement in comparison with other candidate techniques (image-splitting prism and image dissector tube techniques). Another design requirement is speed in acquiring the guide star in order to maximize the time available for science observations. The design constraints are shown parametrically, and modelling results are presented.

The QUEST RR Lyrae Survey. II. The Halo Overdensities in the First Catalog

NASA Astrophysics Data System (ADS)

Vivas, A. Katherina; Zinn, Robert

2006-08-01

The first catalog of the RR Lyrae stars (RRLSs) in the Galactic halo by the Quasar Equatorial Survey Team (QUEST) has been searched for significant overdensities that may be debris from disrupted dwarf galaxies or globular clusters. These RRLSs are contained in a band ~2.3d wide in declination that spans ~165° in right ascension and lie ~4 to ~60 kpc from the Sun. Away from the major overdensities, the distribution of these stars is adequately fitted by a smooth halo model, in which the flattening of the halo decreases with increasing galactocentric distance (as reported by Preston et al.). This model was used to estimate the ``background'' of RRLSs on which the halo overdensities are overlaid. A procedure was developed for recognizing groups of stars that constitute significant overdensities with respect to this background. To test this procedure, a Monte Carlo routine was used to make artificial RRLS surveys that follow the smooth halo model but with Poisson-distributed noise in the numbers of RRLSs and, within limits, random variations in the positions and magnitudes of the artificial stars. The 104 artificial surveys created by this routine were examined for significant groups in exactly the same way as the QUEST survey. These calculations provided estimates of the frequencies with which random fluctuations produce significant groups. In the QUEST survey there are six significant overdensities that contain six or more stars and several smaller ones. The small ones and possibly one or two of the larger ones may be artifacts of statistical fluctuations, and they need to be confirmed by measurements of radial velocity and/or proper motion. The most prominent groups are the northern stream from the Sagittarius dwarf spheroidal galaxy and a large group in Virgo, formerly known as the ``12.4 hr clump,'' which Duffau and coworkers have recently shown to contain a stellar stream (the Virgo stellar stream). Two other groups lie in the direction of the Monoceros stream and at approximately the right distance for membership. Another group is related to the globular cluster Palomar 5.

Natural and artificial spectral edges in exoplanets

NASA Astrophysics Data System (ADS)

Lingam, Manasvi; Loeb, Abraham

2017-09-01

Technological civilizations may rely upon large-scale photovoltaic arrays to harness energy from their host star. Photovoltaic materials, such as silicon, possess distinctive spectral features, including an 'artificial edge' that is characteristically shifted in wavelength shortwards of the 'red edge' of vegetation. Future observations of reflected light from exoplanets would be able to detect both natural and artificial edges photometrically, if a significant fraction of the planet's surface is covered by vegetation or photovoltaic arrays, respectively. The stellar energy thus tapped can be utilized for terraforming activities by transferring heat and light from the day side to the night side on tidally locked exoplanets, thereby producing detectable artefacts.

An artificial neural network to discover hypervelocity stars: candidates in Gaia DR1/TGAS

NASA Astrophysics Data System (ADS)

Marchetti, T.; Rossi, E. M.; Kordopatis, G.; Brown, A. G. A.; Rimoldi, A.; Starkenburg, E.; Youakim, K.; Ashley, R.

2017-09-01

The paucity of hypervelocity stars (HVSs) known to date has severely hampered their potential to investigate the stellar population of the Galactic Centre and the Galactic potential. The first Gaia data release (DR1, 2016 September 14) gives an opportunity to increase the current sample. The challenge is the disparity between the expected number of HVSs and that of bound background stars. We have applied a novel data mining algorithm based on machine learning techniques, an artificial neural network, to the Tycho-Gaia astrometric solution catalogue. With no pre-selection of data, we could exclude immediately ˜99 per cent of the stars in the catalogue and find 80 candidates with more than 90 per cent predicted probability to be HVSs, based only on their position, proper motions and parallax. We have cross-checked our findings with other spectroscopic surveys, determining radial velocities for 30 and spectroscopic distances for five candidates. In addition, follow-up observations have been carried out at the Isaac Newton Telescope for 22 stars, for which we obtained radial velocities and distance estimates. We discover 14 stars with a total velocity in the Galactic rest frame >400 km s-1, and five of these have a probability of >50 per cent of being unbound from the Milky Way. Tracing back their orbits in different Galactic potential models, we find one possible unbound HVS with v ˜ 520 km s-1, five bound HVSs and, notably, five runaway stars with median velocity between 400 and 780 km s-1. At the moment, uncertainties in the distance estimates and ages are too large to confirm the nature of our candidates by narrowing down their ejection location, and we wait for future Gaia releases to validate the quality of our sample. This test successfully demonstrates the feasibility of our new data-mining routine.

Observations of the star Cor Caroli at the Apple Valley Workshop 2016

NASA Astrophysics Data System (ADS)

Estrada, Reed; Boyd, Sidney; Estrada, Chris; Evans, Cody; Rhoades, Hannah; Rhoades, Mark; Rhoades, Trevor

2017-06-01

Using a 22-inch Newtonian Alt/Az telescope and Celestron Micro Guide eyepiece, students participating in a workshop observed the binary star Cor Caroli (STF 1692) and found a position angle of 231.0 degrees as well as an average separation of 18.7" This observation compared favorably with the 2015 Washington Double Star published position. This project was part of Mark Brewer's Apple Valley Double Star Workshop. The results were analyzed using bias and circle error probability calculations.

[Advances in the research of application of artificial intelligence in burn field].

PubMed

Li, H H; Bao, Z X; Liu, X B; Zhu, S H

2018-04-20

Artificial intelligence has been able to automatically learn and judge large-scale data to some extent. Based on database of a large amount of burn data and in-depth learning, artificial intelligence can assist burn surgeons to evaluate burn surface, diagnose burn depth, guide fluid supply during shock stage, and predict prognosis, with high accuracy. With the development of technology, artificial intelligence can provide more accurate information for burn surgeons to make clinical diagnosis and treatment strategies.

Circumscribing Circumscription. A Guide to Relevance and Incompleteness,

DTIC Science & Technology

1985-10-01

other rules of conjecture, to account for resource limitations. P "- h’ MASSACHUSETTS INSTITUTE OF TECHNOLOGY ARTIFICIAL INTELLIGENCE LABORATORY A.I. Memo...of conjecture, to account for resource limitations. This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts...Institute of Technology. Support for the laboratory’s artificial intelligence research is provided in part by the Advanced Research Projects Agency

Optomechanical design of TMT NFIRAOS Subsystems at INO

NASA Astrophysics Data System (ADS)

Lamontagne, Frédéric; Desnoyers, Nichola; Grenier, Martin; Cottin, Pierre; Leclerc, Mélanie; Martin, Olivier; Buteau-Vaillancourt, Louis; Boucher, Marc-André; Nash, Reston; Lardière, Olivier; Andersen, David; Atwood, Jenny; Hill, Alexis; Byrnes, Peter W. G.; Herriot, Glen; Fitzsimmons, Joeleff; Véran, Jean-Pierre

2017-08-01

The adaptive optics system for the Thirty Meter Telescope (TMT) is the Narrow-Field InfraRed Adaptive Optics System (NFIRAOS). Recently, INO has been involved in the optomechanical design of several subsystems of NFIRAOS, including the Instrument Selection Mirror (ISM), the NFIRAOS Beamsplitters (NBS), and the NFIRAOS Source Simulator system (NSS) comprising the Focal Plane Mask (FPM), the Laser Guide Star (LGS) sources, and the Natural Guide Star (NGS) sources. This paper presents an overview of these subsystems and the optomechanical design approaches used to meet the optical performance requirements under environmental constraints.

Ada Implementation Guide. Software Engineering With Ada. Volume 1

DTIC Science & Technology

1994-04-01

Staff, Department ofDefense Dictionary of Military and Associated Terms, Washington, D.C., 1989. STARS McDonal , C., and S . Redwine, *STARS Glossary: A...ADýA28 357> offj I Volume I I SI I t Ada Implementation II Guide 5 Software Engineering With AdaI I S DTIC QUALITY INSPECTED S 5 April 1994 g " 94...and Abbreviations ...................... I I N p a S I I I i I Libt of F4g u OW Tahl Figures 2-1 DON Directives and Instructions for Implementing Public

A near-infrared tip-tilt sensor for the Keck I laser guide star adaptive optics system

NASA Astrophysics Data System (ADS)

Wizinowich, Peter; Smith, Roger; Biasi, Roberto; Cetre, Sylvain; Dekany, Richard; Femenia-Castella, Bruno; Fucik, Jason; Hale, David; Neyman, Chris; Pescoller, Dietrich; Ragland, Sam; Stomski, Paul; Andrighettoni, Mario; Bartos, Randy; Bui, Khanh; Cooper, Andrew; Cromer, John; van Dam, Marcos; Hess, Michael; James, Ean; Lyke, Jim; Rodriguez, Hector; Stalcup, Thomas

2014-07-01

The sky coverage and performance of laser guide star (LGS) adaptive optics (AO) systems is limited by the natural guide star (NGS) used for low order correction. This limitation can be dramatically reduced by measuring the tip and tilt of the NGS in the near-infrared where the NGS is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We present the design of a near-infrared tip-tilt sensor that has recently been integrated with the Keck I telescope's LGS AO system along with some initial on-sky results. The implementation involved modifications to the AO bench, real-time control system, and higher level controls and operations software that will also be discussed. The tip-tilt sensor is a H2RG-based near-infrared camera with 0.05 arc second pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2×2 to 16×16 pixels, centered on an NGS anywhere in the 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beamsplitters located in front of the OSIRIS integral field spectrograph.

CCD Centroiding Experiment for Correcting a Distorted Image on the Focal Plane

NASA Astrophysics Data System (ADS)

Yano, Taihei; Araki, Hiroshi; Gouda, Naoteru; Kobayashi, Yukiyasu; Tsujimoto, Takuji; Nakajima, Tadashi; Kawano, Nobuyuki; Tazawa, Seiichi; Yamada, Yoshiyuki; Hanada, Hideo; Asari, Kazuyoshi; Tsuruta, Seiitsu

2006-10-01

JASMINE (Japan Astrometry Satellite Mission for Infrared Exploration) and ILOM (In situ Lunar Orientation Measurement) are space missions that are in progress at the National Astronomical Observatory of Japan. These two projects require a common astrometric technique to obtain precise positions of star images on solid-state detectors in order to accomplish their objectives. In the laboratory, we have carried out measurements of the centroid of artificial star images on a CCD array in order to investigate the precision of the positions of the stars, using an algorithm for estimating them from photon-weighted means of the stars. In the calibration of the position of a star image at the focal plane, we have also taken into account the lowest order distortion due to optical aberrations, which is proportional to the cube of the distance from the optical axis. Accordingly, we find that the precision of the measurement for the positions of the stars reaches below 1/100 pixel for one measurement.

Image registration for daylight adaptive optics.

PubMed

Hart, Michael

2018-03-15

Daytime use of adaptive optics (AO) at large telescopes is hampered by shot noise from the bright sky background. Wave-front sensing may use a sodium laser guide star observed through a magneto-optical filter to suppress the background, but the laser beacon is not sensitive to overall image motion. To estimate that, laser-guided AO systems generally rely on light from the object itself, collected through the full aperture of the telescope. Daylight sets a lower limit to the brightness of an object that may be tracked at rates sufficient to overcome the image jitter. Below that limit, wave-front correction on the basis of the laser alone will yield an image that is approximately diffraction limited but that moves randomly. I describe an iterative registration algorithm that recovers high-resolution long-exposure images in this regime from a rapid series of short exposures with very low signal-to-noise ratio. The technique takes advantage of the fact that in the photon noise limit there is negligible penalty in taking short exposures, and also that once the images are recorded, it is not necessary, as in the case of an AO tracker loop, to estimate the image motion correctly and quickly on every cycle. The algorithm is likely to find application in space situational awareness, where high-resolution daytime imaging of artificial satellites is important.

Exploring galaxy evolution with latent space walks

NASA Astrophysics Data System (ADS)

Schawinski, Kevin; Turp, Dennis; Zhang, Ce

2018-01-01

We present a new approach using artificial intelligence to perform data-driven forward models of astrophysical phenomena. We describe how a variational autoencoder can be used to encode galaxies to latent space, independently manipulate properties such as the specific star formation rate, and return it to real space. Such transformations can be used for forward modeling phenomena using data as the only constraints. We demonstrate the utility of this approach using the question of the quenching of star formation in galaxies.

Families of Plausible Solutions to the Puzzle of Boyajian’s Star

NASA Astrophysics Data System (ADS)

Wright, Jason T.; Sigurdsson, Steinn

2016-09-01

Good explanations for the unusual light curve of Boyajian's Star have been hard to find. Recent results by Montet & Simon lend strength and plausibility to the conclusion of Schaefer that in addition to short-term dimmings, the star also experiences large, secular decreases in brightness on decadal timescales. This, combined with a lack of long-wavelength excess in the star's spectral energy distribution, strongly constrains scenarios involving circumstellar material, including hypotheses invoking a spherical cloud of artifacts. We show that the timings of the deepest dimmings appear consistent with being randomly distributed, and that the star's reddening and narrow sodium absorption is consistent with the total, long-term dimming observed. Following Montet & Simon's encouragement to generate alternative hypotheses, we attempt to circumscribe the space of possible explanations with a range of plausibilities, including: a cloud in the outer solar system, structure in the interstellar medium (ISM), natural and artificial material orbiting Boyajian's Star, an intervening object with a large disk, and variations in Boyajian's Star itself. We find the ISM and intervening disk models more plausible than the other natural models.

A Starter's Guide to Artificial Intelligence.

ERIC Educational Resources Information Center

McConnell, Barry A.; McConnell, Nancy J.

1988-01-01

Discussion of the history and development of artificial intelligence (AI) highlights a bibliography of introductory books on various aspects of AI, including AI programing; problem solving; automated reasoning; game playing; natural language; expert systems; machine learning; robotics and vision; critics of AI; and representative software. (LRW)

Characterizing the Hercules Thick Disk Cloud

DTIC Science & Technology

2009-01-01

merger. Key Words: Astronomy , Hercules Thick Disk Cloud, Galaxy, Star Count, Color, Photometric Parallax 2 Contents Chapter 1... Astronomy : Structure and Kinematics, 2nd ed., New York: W. H. Freeman and Company, 1981, pp 4. 5 Henbest, Guide, pp 10. 6 Mihalas, Galactic, pp 209...studies of astronomy later in his life, he focused on binary star systems and concluded that not all stars have the same absolute magnitude, thus

The INT Search for Metal-Poor Stars: Spectroscopic Observations and Classification via Artificial Neural Networks

NASA Astrophysics Data System (ADS)

Allende Prieto, Carlos; Rebolo, Rafael; García López, Ramón J.; Serra-Ricart, Miquel; Beers, Timothy C.; Rossi, Silvia; Bonifacio, Piercarlo; Molaro, Paolo

2000-09-01

With the dual aims of enlarging the list of extremely metal-poor stars identified in the Galaxy and boosting the numbers of moderately metal-deficient stars in directions that sample the rotational properties of the thick disk, we have used the 2.5 m Isaac Newton Telescope and the Intermediate Dispersion Spectrograph to carry out a survey of brighter (primarily northern hemisphere) metal-poor candidates selected from the HK objective-prism-interference-filter survey of Beers and collaborators. Over the course of only three observing runs (15 nights) we have obtained medium-resolution (λ/δλ~=2000) spectra for 1203 objects (V~=11-15). Spectral absorption-line indices and radial velocities have been measured for all the candidates. Metallicities, quantified by [Fe/H], and intrinsic (B-V)0 colors have been estimated for 731 stars with effective temperatures cooler than roughly 6500 K by using artificial neural networks (ANNs) trained with spectral indices. We show that this method performs as well as a previously explored Ca II K calibration technique, yet it presents some practical advantages. Among the candidates in our sample we identify 195 stars with [Fe/H]<=-1.0, 67 stars with [Fe/H]<=-2.0, and 12 new stars with [Fe/H]<=-3.0. Although the effective yield of metal-poor stars in our sample is not as large as that in previous HK survey follow-up programs, the rate of discovery per unit of telescope time is quite high. Further development of the ANN technique, with the networks being fed the entire spectrum, rather than just the spectral indices, holds the promise to produce fast, accurate, multidimensional spectral classifications (with the associated physical parameter estimates), as is required to process the large data flow provided by present and future instrumentation. Based on observations made with the Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

The ARGOS laser system: green light for ground layer adaptive optics at the LBT

NASA Astrophysics Data System (ADS)

Raab, Walfried; Rabien, Sebastian; Gässler, Wolfgang; Esposito, Simone; Barl, Lothar; Borelli, Jose; Daysenroth, Matthias; Gemperlein, Hans; Kulas, Martin; Ziegleder, Julian

2014-07-01

We report on the development of the laser system of ARGOS, the multiple laser guide star adaptive optics system for the Large Binocular Telescope (LBT). The system uses a total of six high powered, pulsed Nd:YAG lasers frequency-doubled to a wavelength of 532 nm to generate a set of three guide stars above each of the LBT telescopes. The position of each of the LGS constellations on sky as well as the relative position of the individual laser guide stars within this constellation is controlled by a set of steerable mirrors and a fast tip-tilt mirror within the laser system. The entire opto-mechanical system is housed in two hermetically sealed and thermally controlled enclosures on the SX and DX side of the LBT telescope. The laser beams are propagated through two refractive launch telescopes which focus the beams at an altitude of 12 km, creating a constellation of laser guide stars around a 4 arcminute diameter circle by means of Rayleigh scattering. In addition to the GLAO Rayleigh beacon system, ARGOS has also been designed for a possible future upgrade with a hybrid sodium laser - Rayleigh beacon combination, enabling diffraction limited operation. The ARGOS laser system was successfully installed at the LBT in April 2013. Extensive functional tests have been carried out and have verified the operation of the systems according to specifications. The alignment of the laser system with respect to the launch telescope was carried out during two more runs in June and October 2013, followed by the first propagation of laser light on sky in November 2013.

Astronomy: A Self-Teaching Guide, 6th Edition

NASA Astrophysics Data System (ADS)

Moché, Dinah L.

2004-02-01

"A lively, up-to-date account of the basic principles of astronomy and exciting current field of research."-Science Digest For a quarter of a century, Astronomy: A Self-Teaching Guide has been making students and amateur stargazers alike feel at home among the stars. From stars, planets and galaxies, to black holes, the Big Bang and life in space, this title has been making it easy for beginners to quickly grasp the basic concepts of astronomy for over 25 years. Updated with the latest discoveries in astronomy and astrophysics, this newest edition of Dinah Moché's classic guide now includes many Web site addresses for spectacular images and news. And like all previous editions, it is packed with valuable tables, charts, star and moon maps and features simple activities that reinforce readers' grasp of basic concepts at their own pace, as well as objectives, reviews, and self-tests to monitor their progress. Dinah L. Moché, PhD (Rye, NY), is an award-winning author, educator, and lecturer. Her books have sold over nine million copies in seven languages.

Observations of the Star Cor Caroli at the Apple Valley Workshop 2016 (Abstract)

NASA Astrophysics Data System (ADS)

Estrada, R.; Boyd, S.; Estrada, C.; Evans, C.; Rhoades, H.; Rhoades, M.; Rhoades, T.

2017-12-01

(Abstract only) Using a 22-inch Newtonian Alt/Az telescope and Celestron Micro Guide eyepiece, students participating in a workshop observed the binary star Cor Caroli (STF 1692; alpha CVn) and found a position angle of 231.0 degrees as well as an average separation of 18.7" This observation compared favorably with the 2015 Washington Double Star published position. This project was part of Mark Brewer's Apple Valley Double Star Workshop. The results were analyzed using bias and circle error probability calculations.

Star Trek with Latin. Teacher's Guide. Tentative Edition.

ERIC Educational Resources Information Center

Masciantonio, Rudolph; And Others

The purpose of this guide is to assist Latin and English teachers with some background in Latin to expand the English vocabulary and reading skills of students through the study of Latin roots, prefixes, and suffixes. The introductory material in the guide provides general notes on the teaching of Latin in the Philadelphia School District,…

Sign of the Zodiac as a predictor of survival for recipients of an allogeneic stem cell transplant for chronic myeloid leukaemia (CML): an artificial association.

PubMed

Szydlo, R M; Gabriel, I; Olavarria, E; Apperley, J

2010-10-01

Astrological or Zodiac (star) sign has been shown to be a statistically significant factor in the outcome of a variety of diseases, conditions, and phenomena. To investigate its relevance in the context of a stem cell transplant (SCT), we examined its influence in chronic myeloid leukaemia, a disease with well-established prognostic factors. Data were collected on 626 patients who received a first myeloablative allogeneic SCT between 1981 and 2006. Star sign was determined for each patient. Univariate analyses comparing all 12 individual star signs showed considerable variation of 5-year probabilities of survival, 63% for Arians, to 45% for Aquarians, but without significance (P=.65). However, it was possible to pool together star signs likely to provide dichotomous results. Thus, grouping together Aries, Taurus, Gemini, Leo, Scorpio, and Capricorn (group A; n=317) versus others (group B; n=309) resulted in a highly significant difference (58% vs 48%; P=.007). When adjusted for known prognostic factors in a multivariate analysis, group B was associated with an increased risk of mortality when compared with group A (relative risk [RR], 1.37; P=.005). In this study, we show that, providing adequate care is taken, a significant relationship between patient star sign and survival post SCT for CML can be observed. This is, however, a completely erroneous result, and is based on the pooling together of observations to artificially create a statistically significant result. Statistical analyses should thus be carried out on a priori hypotheses and not to find a meaningful or significant result. Copyright © 2010 Elsevier Inc. All rights reserved.

Evaluating potential spectral impacts of various artificial lights on melatonin suppression, photosynthesis, and star visibility.

PubMed

Aubé, Martin; Roby, Johanne; Kocifaj, Miroslav

2013-01-01

Artificial light at night can be harmful to the environment, and interferes with fauna and flora, star visibility, and human health. To estimate the relative impact of a lighting device, its radiant power, angular photometry and detailed spectral power distribution have to be considered. In this paper we focus on the spectral power distribution. While specific spectral characteristics can be considered harmful during the night, they can be considered advantageous during the day. As an example, while blue-rich Metal Halide lamps can be problematic for human health, star visibility and vegetation photosynthesis during the night, they can be highly appropriate during the day for plant growth and light therapy. In this paper we propose three new indices to characterize lamp spectra. These indices have been designed to allow a quick estimation of the potential impact of a lamp spectrum on melatonin suppression, photosynthesis, and star visibility. We used these new indices to compare various lighting technologies objectively. We also considered the transformation of such indices according to the propagation of light into the atmosphere as a function of distance to the observer. Among other results, we found that low pressure sodium, phosphor-converted amber light emitting diodes (LED) and LED 2700 K lamps filtered with the new Ledtech's Equilib filter showed a lower or equivalent potential impact on melatonin suppression and star visibility in comparison to high pressure sodium lamps. Low pressure sodium, LED 5000 K-filtered and LED 2700 K-filtered lamps had a lower impact on photosynthesis than did high pressure sodium lamps. Finally, we propose these indices as new standards for the lighting industry to be used in characterizing their lighting technologies. We hope that their use will favor the design of new environmentally and health-friendly lighting technologies.

Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility

PubMed Central

Aubé, Martin; Roby, Johanne; Kocifaj, Miroslav

2013-01-01

Artificial light at night can be harmful to the environment, and interferes with fauna and flora, star visibility, and human health. To estimate the relative impact of a lighting device, its radiant power, angular photometry and detailed spectral power distribution have to be considered. In this paper we focus on the spectral power distribution. While specific spectral characteristics can be considered harmful during the night, they can be considered advantageous during the day. As an example, while blue-rich Metal Halide lamps can be problematic for human health, star visibility and vegetation photosynthesis during the night, they can be highly appropriate during the day for plant growth and light therapy. In this paper we propose three new indices to characterize lamp spectra. These indices have been designed to allow a quick estimation of the potential impact of a lamp spectrum on melatonin suppression, photosynthesis, and star visibility. We used these new indices to compare various lighting technologies objectively. We also considered the transformation of such indices according to the propagation of light into the atmosphere as a function of distance to the observer. Among other results, we found that low pressure sodium, phosphor-converted amber light emitting diodes (LED) and LED 2700 K lamps filtered with the new Ledtech’s Equilib filter showed a lower or equivalent potential impact on melatonin suppression and star visibility in comparison to high pressure sodium lamps. Low pressure sodium, LED 5000 K-filtered and LED 2700 K-filtered lamps had a lower impact on photosynthesis than did high pressure sodium lamps. Finally, we propose these indices as new standards for the lighting industry to be used in characterizing their lighting technologies. We hope that their use will favor the design of new environmentally and health-friendly lighting technologies. PMID:23861808

Modeling update for the Thirty Meter Telescope laser guide star dual-conjugate adaptive optics system

NASA Astrophysics Data System (ADS)

Gilles, Luc; Wang, Lianqi; Ellerbroek, Brent

2010-07-01

This paper describes the modeling efforts undertaken in the past couple of years to derive wavefront error (WFE) performance estimates for the Narrow Field Infrared Adaptive Optics System (NFIRAOS), which is the facility laser guide star (LGS) dual-conjugate adaptive optics (AO) system for the Thirty Meter Telescope (TMT). The estimates describe the expected performance of NFIRAOS as a function of seeing on Mauna Kea, zenith angle, and galactic latitude (GL). They have been developed through a combination of integrated AO simulations, side analyses, allocations, lab and lidar experiments.

A walk through the heavens : a guide to stars and constellations and their legends

NASA Astrophysics Data System (ADS)

Heifetz, Milton D.; Tirion, Wil

What star is that? Where's the Great Bear? Who was Andromeda? A Walk through the Heavens is your guide to the pathways of the night sky, answering the commonest questions about what you can see up there. There are simplified maps of the constellations, together with instructions on how to gauge their sizes and the distances between them. With this information you can find the constellations easily, and make a journey by eye from one constellation to the next. Ancient myths surrounding the constellations are retold, enriching our understanding of how historical peoples saw the awe-inspiring spectacle of a sky sprinkled with stars. This book, magically illustrated by Wil Tirion, does not require any instrument or telescope. It is an ideal introduction to launch a young astronomer on a journey across starlit skies.

Reference Collections and Standards.

ERIC Educational Resources Information Center

Winkel, Lois

1999-01-01

Reviews six reference materials for young people: "The New York Public Library Kid's Guide to Research"; "National Audubon Society First Field Guide. Mammals"; "Star Wars: The Visual Dictionary"; "Encarta Africana"; "World Fact Book, 1998"; and "Factastic Book of 1001 Lists". Includes ordering information.(AEF)

Student Measurements of STFA 14 AC at Vanguard Preparatory School

NASA Astrophysics Data System (ADS)

Gillette, Sean; Archuleta, Alex; Diaz, Lizbeth; Gillespie, Kyle; Gosney, Timothy; Johnson, Stephen; Mohan, Nikita; Rajacich, Jacob; Roehl, Nathaniel; Sharpe, Scotty; Whitt, Kahaloha

2016-01-01

Eighth grade students at Vanguard Preparatory School measured the double star STFA 14 AC using a Bader Planetarium Micro Guide eyepiece. Navi (Gamma Cassiopeiae) was used as the ca libration star. The calculated means of multiple observations of STFA 14 AC resulted in a separation of 53.3" and a position angle of 2.0°. These measurements were compared to the most recent values in the Washington Double Star Catalog.

A Traveler's Guide to the Universe

ERIC Educational Resources Information Center

Darling, Gerald

2012-01-01

Elementary school students are intensely curious about astronomy: the Moon, planets, stars, and galaxies. Summer, with its warm evenings and star-filled skies, is the perfect time for students to explore the cosmos with a pair of binoculars. Because binoculars are used for many purposes (sporting events or birding, for example), many families…

Fairbanks North Star borough rural roads upgrade inventory and cost estimation software user guide : version I.

DOT National Transportation Integrated Search

2013-04-01

The Rural Road Upgrade Inventory and Cost Estimation Software is designed by the AUTC : research team to help the Fairbanks North Star Borough (FNSB) estimate the cost of upgrading : rural roads located in the Borough's Service Areas. The Software pe...

Biology Students Building Computer Simulations Using StarLogo TNG

ERIC Educational Resources Information Center

Smith, V. Anne; Duncan, Ishbel

2011-01-01

Confidence is an important issue for biology students in handling computational concepts. This paper describes a practical in which honours-level bioscience students simulate complex animal behaviour using StarLogo TNG, a freely-available graphical programming environment. The practical consists of two sessions, the first of which guides students…

The ASTRA Spectrophotometer: Design and Overview

NASA Astrophysics Data System (ADS)

Adelman, S. J.; Gulliver, A. F.; Smalley, B.; Pazder, J. S.; Younger, P. F.; Boyd, L. J.; Epand, D.; Younger, T.

2007-04-01

The ASTRA Cassegrain Spectrophotometer and its automated 0.5-m f/16 telescope will soon be working together at the Fairborn Observatory near Nogales, Arizona. Scientific observations are expected to begin in 2007. We provide an overview of this project and review the design of the system. A separate paper in these Proceedings presents details of the data reduction and flux calibrations. The Nogales site averages 150 photometric nights per year. ASTRA should observe stars whose declinations are in the range +80° to -35°. In an hour the system should obtain S/N = 200 observations of stars as faint as 9.5 mag after correction for instrumental errors. Vega will require about 25 seconds for observation and CCD readout. Usually the telescope will find its next target in less than a minute. A small CCD camera finds and centers the target and a second then guides on the zeroth order spectrum. The spectrophotometer uses both a grating and a cross-dispersing prism to produce spectra from both the first and the second orders simultaneously. The square 30 arc second sky fields for each order do not overlap. The resolution is 7 Å in second and 14 Å in first order. The wavelength range is approximately λλ3300-9000. We are initially using about 10 minutes/hour to observe Vega and secondary standard candidates. Our scientific CCD is electronically cooled to -50° C with a water recirculation system heat sink. The same 4° C recycling water system provides thermal stabilization of the instrument. Our flat fielding system uses a second 0.5-m telescope to produce a collimated beam from a 100 μm pinhole illuminated by a quartz halogen lamp. When the two telescopes point at one another this ``artificial star" is focused by the ASTRA telescope which is then rocked to expose the image from the top to the bottom of the entrance aperture. A LINUX HP server at The Citadel will have databases of ASTRA observations. Each observing request has its own priority and observing window, ASTRA can observe standard stars at a regular rate throughout the night, any accessible target at a given time, and variable stars. ASTRA will produce considerable high quality data.

VizieR Online Data Catalog: OGLE II SMC eclipsing binaries (Wyrzykowski+, 2004)

NASA Astrophysics Data System (ADS)

Wyrzykowski, L.; Udalski, A.; Kubiak, M.; Szymanski, M. K.; Zebrun, K.; Soszinski, I.; Wozniak, P. R.; Pietrzynski, G.; Szewczyk, O.

2009-03-01

We present new version of the OGLE-II catalog of eclipsing binary stars detected in the Small Magellanic Cloud, based on Difference Image Analysis catalog of variable stars in the Magellanic Clouds containing data collected from 1997 to 2000. We found 1351 eclipsing binary stars in the central 2.4 square degree area of the SMC. 455 stars are newly discovered objects, not found in the previous release of the catalog. The eclipsing objects were selected with the automatic search algorithm based on the artificial neural network. The full catalog with individual photometry is accessible from the OGLE INTERNET archive, at ftp://sirius.astrouw.edu.pl/ogle/ogle2/var_stars/smc/ecl . Regular observations of the SMC fields started on June 26, 1997 and covered about 2.4 square degrees of central parts of the SMC. Reductions of the photometric data collected up to the end of May 2000 were performed with the Difference Image Analysis (DIA) package. (1 data file).

Hypervelocity star candidates in Gaia DR1/TGAS

NASA Astrophysics Data System (ADS)

Marchetti, T.; Rossi, E. M.; Kordopatis, G.; Brown, A. G. A.; Rimoldi, A.; Starkenburg, E.; Youakim, K.; Ashley, R.

2018-04-01

Hypervelocity stars (HVSs) are characterized by a total velocity in excess of the Galactic escape speed, and with trajectories consistent with coming from the Galactic Centre. We apply a novel data mining routine, an artificial neural network, to discover HVSs in the TGAS subset of the first data release of the Gaia satellite, using only the astrometry of the stars. We find 80 stars with a predicted probability >90% of being HVSs, and we retrieved radial velocities for 47 of those. We discover 14 objects with a total velocity in the Galactic rest frame >400 km s-1, and 5 of these have a probability >50% of being unbound from the Milky Way. Tracing back orbits in different Galactic potentials, we discover 1 HVS candidate, 5 bound HVS candidates, and 5 runaway star candidates with remarkably high velocities, between 400 and 780 km s-1. We wait for future Gaia releases to confirm the goodness of our sample and to increase the number of HVS candidates.

Methods for correcting tilt anisoplanatism in laser-guide-star-based multiconjugate adaptive optics.

PubMed

Ellerbroek, B L; Rigaut, F

2001-10-01

Multiconjugate adaptive optics (MCAO) is a technique for correcting turbulence-induced phase distortions in three dimensions instead of two, thereby greatly expanding the corrected field of view of an adaptive optics system. This is accomplished with use of multiple deformable mirrors conjugate to distinct ranges in the atmosphere, with actuator commands computed from wave-front sensor (WFS) measurements from multiple guide stars. Laser guide stars (LGSs) must be used (at least for the forseeable future) to achieve a useful degree of sky coverage in an astronomical MCAO system. Much as a single LGS cannot be used to measure overall wave-front tilt, a constellation of multiple LGSs at a common range cannot detect tilt anisoplanatism. This error alone will significantly degrade the performance of a MCAO system based on a single tilt-only natural guide star (NGS) and multiple tilt-removed LGSs at a common altitude. We present a heuristic, low-order model for the principal source of tilt anisoplanatism that suggests four possible approaches to eliminating this defect in LGS MCAO: (i) tip/tilt measurements from multiple NGS, (ii) a solution to the LGS tilt uncertainty problem, (iii) additional higher-order WFS measurements from a single NGS, or (iv) higher-order WFS measurements from both sodium and Rayleigh LGSs at different ranges. Sample numerical results for one particular MCAO system configuration indicate that approach (ii), if feasible, would provide the highest degree of tilt anisoplanatism compensation. Approaches (i) and (iv) also provide very useful levels of performance and do not require unrealistically low levels of WFS measurement noise. For a representative set of parameters for an 8-m telescope, the additional laser power required for approach (iv) is on the order of 2 W per Rayleigh LGS.

The First Light of the Subaru Laser Guide Star Adaptive Optics System

NASA Astrophysics Data System (ADS)

Takami, H.; Hayano, Y.; Oya, S.; Hattori, M.; Watanabe, M.; Guyon, O.; Eldred, M.; Colley, S.; Saito, Y.; Itoh, M.; Dinkins, M.

Subaru Telescope has been operating 36 element curvature sensor AO system for the Cassegrain focus since 2000. We have developed a new AO system for the Nasmyth focus. The AO system has 188 element curvature wavefront sensor and bimorph deformable mirror. It is the largest format system for this type of sensor . The deformable mirror has also 188 element with 90 mm effective aperture and 130 mm blank size. The real time controller is 4 CPU real time Linux OS computer and the update speed is now 1.5 kHz. The AO system also has laser guide star system. The laser is sum frequency solid state laser generating 589 nm light. We have achieved 4.7 W output power with excellent beam quality of M^2=1.1 and good stability. The laser is installed in a clean room on the Nasmyth platform. The laser beam is transferred by photonic crystal optical fiber with 35 m to the 50 cm laser launching telescope mounted behind the Subaru 2ry mirror. The field of view of the low order wavefront sensor for tilt guide star in LGS mode is 2.7 arcmin in diameter. The AO system had the first light with natural guide star in October 2006. The Strehl ratio was > 0.5 at K band under the 0.8 arcsec visible seeing. We also has projected laser beam on the sky during the same engineering run. Three instruments will be used with the AO system. Infrared camera and spectrograph (IRCS), High dynamic range IR camera (HiCIAO) for exosolar planet detection, and visible 3D spectrograph.

Secular Dynamical Anti-friction in Galactic Nuclei

NASA Astrophysics Data System (ADS)

Madigan, Ann-Marie; Levin, Yuri

2012-07-01

We identify a gravitational-dynamical process in near-Keplerian potentials of galactic nuclei that occurs when an intermediate-mass black hole (IMBH) is migrating on an eccentric orbit through the stellar cluster towards the central supermassive black hole. We find that, apart from conventional dynamical friction, the IMBH experiences an often much stronger systematic torque due to the secular (i.e., orbit-averaged) interactions with the cluster's stars. The force which results in this torque is applied, counterintuitively, in the same direction as the IMBH's precession and we refer to its action as "secular dynamical anti-friction" (SDAF). We argue that SDAF, and not the gravitational ejection of stars, is responsible for the IMBH's eccentricity increase seen in the initial stages of previous N-body simulations. Our numerical experiments, supported by qualitative arguments, demonstrate that (1) when the IMBH's precession direction is artificially reversed, the torque changes sign as well, which decreases the orbital eccentricity; (2) the rate of eccentricity growth is sensitive to the IMBH migration rate, with zero systematic eccentricity growth for an IMBH whose orbit is artificially prevented from inward migration; and (3) SDAF is the strongest when the central star cluster is rapidly rotating. This leads to eccentricity growth/decrease for the clusters rotating in the opposite/same direction relative to the IMBH's orbital motion.

SETI at X-energies - parasitic searches from astrophysical observations.

NASA Astrophysics Data System (ADS)

Corbet, R. H. D.

1997-01-01

If a sufficiently advanced civilization can either modulate the emission from an X-ray binary, or make use of the natural high luminosity to power an artificial transmitter, these can serve as good beacons for interstellar communication without involving excessive energy costs to the broadcasting civilization. In addition, the small number of X-ray binaries in the Galaxy considerably reduces the number of targets that must be investigated compared to searches in other energy bands. Low mass X-ray binaries containing neutron stars in particular are considered as prime potential natural and artificial beacons and high time resolution (better than 1ms) observations are encouraged. All sky monitors provide the capability of detecting brief powerful artificial signals from isolated neutron stars. New capabilities of X-ray astronomy satellites developed for astrophysical purposes are enabling SETI in new parameter regimes. For example, the X-ray Timing Explorer satellite provides the capability of exploring the sub-millisecond region. Other planned X-ray astronomy satellites should provide significantly improved spectral resolution. While SETI at X-ray energies is highly speculative (and rather unfashionable) by using a parasitic approach little additional cost is involved. The inclusion of X-ray binaries in target lists for SETI at radio and other wavebands is also advocated.

GASOLINE: Smoothed Particle Hydrodynamics (SPH) code

NASA Astrophysics Data System (ADS)

N-Body Shop

2017-10-01

Gasoline solves the equations of gravity and hydrodynamics in astrophysical problems, including simulations of planets, stars, and galaxies. It uses an SPH method that features correct mixing behavior in multiphase fluids and minimal artificial viscosity. This method is identical to the SPH method used in the ChaNGa code (ascl:1105.005), allowing users to extend results to problems requiring >100,000 cores. Gasoline uses a fast, memory-efficient O(N log N) KD-Tree to solve Poisson's Equation for gravity and avoids artificial viscosity in non-shocking compressive flows.

The Monthly Sky Guide: Sixth Edition

NASA Astrophysics Data System (ADS)

Ridpath, Ian; Tirion, Wil

2003-06-01

The latest edition of Ian Ridpath and Wil Tirion's popular guide to the night sky is updated for planet positions and forthcoming eclipses up to the end of the year 2007. With one chapter for each month of the year, this is an easy-to-use handbook for anyone wanting to identify constellations, star clusters, nebulae, to plot the movement of planets, or witness solar and lunar eclipses. Most of the features discussed are visible to the naked eye and all can be seen with a small telescope or binoculars. Ian Ridpath has been a full-time writer, broadcaster and lecturer on astronomy and space for more than twenty-five years. He has written and edited more than 40 books, including A Comet Called Haley (Cambridge, 1985). Wil Tirion made his first star map in 1977. It showed stars to the magnitude of 6.5 and was issued as a set of maps by the British Astronomical Association in 1981. He has illustrated numerous books and magazines, including The Cambridge Star Atlas (Cambridge, 2001). Previous Edition Pb (1999): 0-521-66771-2

SETI at the Nancay radiotelescope.

PubMed

Biraud, F

1983-11-01

The Nancay (France) radiotelescope has been used in June, 1981, to search for artificial monochromatic signals from 102 nearby stars, without success. A different approach to SETI is also considered based on the properties of wide band signals. A detection procedure, through Karhunen-Loeve analysis, is suggested.

Kepler-90 system (Artist's Concept)

NASA Image and Video Library

2017-12-14

Our solar system now is tied for most number of planets around a single star, with the recent discovery of an eighth planet circling Kepler-90, a Sun-like star 2,545 light years from Earth. The planet was discovered in data from NASA's Kepler Space Telescope. The newly-discovered Kepler-90i -- a sizzling hot, rocky planet that orbits its star once every 14.4 days -- was found using machine learning from Google. Machine learning is an approach to artificial intelligence in which computers "learn." In this case, computers learned to identify planets by finding in Kepler data instances where the telescope recorded changes in starlight caused by planets beyond our solar system, known as exoplanets. https://photojournal.jpl.nasa.gov/catalog/PIA22192

The Interplay of Star formation and Accretion in the Local Universe

NASA Astrophysics Data System (ADS)

Green, Paul

2010-09-01

Galaxy evolution and supermassive black hole growth are closely linked, but the inter-relationships between active accretion and star formation, AGN outflows, and host morphological trends remain poorly understood. We propose to study an unprecedented sample of 615 low redshift SDSS galaxies and AGN detected in archival Chandra fields. We will measure diverse optical and X-ray spectroscopic properties spanning the artificial galaxy/AGN divide, and provide detailed results of our model fitting. We highlight tests of (1) an evolutionary sequence from star-forming through AGN to passive galaxy modes (2) narrow line Sy1 galaxies and new parallels between the accretion modes of AGN and stellar mass X-ray binaries and (3) the relationship of host morphology and mergers to accretion.

Which evolutionary status does the Blue Large-Amplitude Pulsators stay at?

NASA Astrophysics Data System (ADS)

Wu, Tao; Li, Yan

2018-05-01

Asteroseismology is a very useful tool for exploring the stellar interiors and evolutionary status and for determining stellar fundamental parameters, such as stellar mass, radius, surface gravity, and the stellar mean density. In the present work, we use it to preliminarily analyze the 14 new-type pulsating stars: Blue Large-Amplitude Pulsators (BLAPs) which is observed by OGLE project, to roughly analyze their evolutionary status. We adopt the theory of single star evolution and artificially set the mass loss rate of \\dot{M}=-2× 10^{-4} M_{⊙}/year and mass loss beginning at the radius of R = 40 R_{⊙} on red giant branch to generate a series of theoretical models. Based on these theoretical models and the corresponding observations, we find that those BLAP stars are more likely to be the core helium burning stars. Most of them are in the middle and late phase of the helium burning.

General visual robot controller networks via artificial evolution

NASA Astrophysics Data System (ADS)

Cliff, David; Harvey, Inman; Husbands, Philip

1993-08-01

We discuss recent results from our ongoing research concerning the application of artificial evolution techniques (i.e., an extended form of genetic algorithm) to the problem of developing `neural' network controllers for visually guided robots. The robot is a small autonomous vehicle with extremely low-resolution vision, employing visual sensors which could readily be constructed from discrete analog components. In addition to visual sensing, the robot is equipped with a small number of mechanical tactile sensors. Activity from the sensors is fed to a recurrent dynamical artificial `neural' network, which acts as the robot controller, providing signals to motors governing the robot's motion. Prior to presentation of new results, this paper summarizes our rationale and past work, which has demonstrated that visually guided control networks can arise without any explicit specification that visual processing should be employed: the evolutionary process opportunistically makes use of visual information if it is available.

Wavefront error budget development for the Thirty Meter Telescope laser guide star adaptive optics system

NASA Astrophysics Data System (ADS)

Gilles, Luc; Wang, Lianqi; Ellerbroek, Brent

2008-07-01

This paper describes the modeling effort undertaken to derive the wavefront error (WFE) budget for the Narrow Field Infrared Adaptive Optics System (NFIRAOS), which is the facility, laser guide star (LGS), dual-conjugate adaptive optics (AO) system for the Thirty Meter Telescope (TMT). The budget describes the expected performance of NFIRAOS at zenith, and has been decomposed into (i) first-order turbulence compensation terms (120 nm on-axis), (ii) opto-mechanical implementation errors (84 nm), (iii) AO component errors and higher-order effects (74 nm) and (iv) tip/tilt (TT) wavefront errors at 50% sky coverage at the galactic pole (61 nm) with natural guide star (NGS) tip/tilt/focus/astigmatism (TTFA) sensing in J band. A contingency of about 66 nm now exists to meet the observatory requirement document (ORD) total on-axis wavefront error of 187 nm, mainly on account of reduced TT errors due to updated windshake modeling and a low read-noise NGS wavefront sensor (WFS) detector. A detailed breakdown of each of these top-level terms is presented, together with a discussion on its evaluation using a mix of high-order zonal and low-order modal Monte Carlo simulations.

Remote Operations of Laser Guide Star Systems: Gemini Observatory.

NASA Astrophysics Data System (ADS)

Oram, Richard J.; Fesquet, Vincent; Wyman, Robert; D'Orgeville, Celine

2011-03-01

The Gemini North telescope, equipped with a 14W laser, has been providing Laser Guide Star Adaptive Optics (LGS AO) regular science queue observations for worldwide astronomers since February 2007. The new 55W laser system for MCAO was installed on the Gemini South telescope in May 2010. In this paper, we comment on how Gemini Observatory developed regular remote operation of the Laser Guide Star Facility and high-power solid-state laser as routine normal operations. Fully remote operation of the LGSF from the Hilo base facility HBF was initially trialed and then optimized and became the standard operating procedure (SOP) for LGS operation in December 2008. From an engineering perspective remote operation demands stable, well characterized and base-lined equipment sets. In the effort to produce consistent, stable and controlled laser parameters (power, wavelength and beam quality) we completed a failure mode effect analysis of the laser system and sub systems that initiated a campaign of hardware upgrades and procedural improvements to the routine maintenance operations. Finally, we provide an overview of normal operation procedures during LGS runs and present a snapshot of data accumulated over several years that describes the overall LGS AO observing efficiency at the Gemini North telescope.

Student Measurements of STFA 10AB (Theta Tauri)

NASA Astrophysics Data System (ADS)

Gillette, Sean; Estrada, Chris; Estrada, Reed; Aguilera, Sophia; Chavez, Valerie; Givens, Jalynn; Lindorfer, Sarah; Michels, Kaylie; Mobley, Makenzie; Reder, Gabriel; Renteria, Kayla; Shattles, Jenna; Wilkin, Aiden; Woodbury, Maisy; Rhoades, Breauna; Rhoades, Mark

2017-04-01

Eighth grade students at Vanguard Preparatory School measured the double star STFA 10AB using a 22-inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece. Bellatrix was used as the calibration star. The calculated means of multiple observations of STFA 10AB resulted in a separation of 45.18,” a scale constant of 7.88 arcseconds per division, and position angle of 257.9°. These measurements were compared to the most recent values in the Washington Double Star Catalog.

Taxonomy and Classification Scheme for Artificial Space Objects

DTIC Science & Technology

2013-09-01

filter UVB and spectroscopic measurements) and albedo (including polarimetry ). Earliest classifications of asteroids [17] were based on the filter...similarities of the asteroid colors to K0 to K2V stars. The first more complete asteroid taxonomy was based on a synthesis of polarimetry , radiometry, and

Soaring through the Universe. Astronomy through Children's Literature.

ERIC Educational Resources Information Center

Letwinch, Joanne C.

This publication is a guide to teaching astronomy through the use of mythology and its literature in grades 3-6. The book is divided into the following seven sections: "Introduction"; Chapter 1: "Luna: the Moon"; Chapter 2: "Del Sol: the Sun"; Chapter 3: "The Planets"; Chapter 4: "Star Bright, Star Light"; Chapter 5: "Traveling through Space"; and…

ALOG user's manual: A Guide to using the spreadsheet-based artificial log generator

Treesearch

Matthew F. Winn; Philip A. Araman; Randolph H. Wynne

2012-01-01

Computer programs that simulate log sawing can be valuable training tools for sawyers, as well as a means oftesting different sawing patterns. Most available simulation programs rely on diagrammed-log databases, which canbe very costly and time consuming to develop. Artificial Log Generator (ALOG) is a user-friendly Microsoft® Excel®...

Mini-Rocket User Guide

DTIC Science & Technology

2007-08-01

26 ISTC Simulation Comparisons ............................................................................... 29 STARS...Range Comparison Figure 8. ISTC Simulntioiz Comparisons 29 Mini-Rocket User Guide REAL-WORLD COMPARISON In particular, note the very high angle-of...not directly model the missile rigid body dynamics. The ISTC subsequently used Mini-Rocket as a driver to stimulate other models and as a risk

The star identification, pointing and tracking system of UVSTAR, an attached payload instrument system for the Shuttle Hitchhiker-M platform

NASA Technical Reports Server (NTRS)

Decarlo, Francesco; Stalio, Roberto; Trampus, Paolo; Broadfoot, A. Lyle; Sandel, Bill R.; Sicuranza, Giovanni

1993-01-01

We describe an algorithm for star identification and pointing/tracking of a spaceborne electro-optical system and simulation analyses to test the algorithm. The algorithm will be implemented in the guiding system of UVSTAR, a spectrographic telescope for observations of astronomical and planetary sources operating in the 500-1250 A waveband at approximately 1 A resolution. The experiment is an attached payload and will fly as a Hitchhiker-M payload on the Shuttle. UVSTAR includes capabilities for independent target acquisition and tracking. The spectrograph package has internal gimbals that allow angular movement of plus or minus 3 deg from the central position. Rotation about the azimuth axis (parallel to the Shuttle z axis) and elevation axis (parallel to the Shuttle x axis) will actively position the field of view to center the target of interest in the fields of the spectrographs. The algorithm is based on an on-board catalog of stars. To identify star fields, the algorithm compares the positions of stars recorded by the guiding imager to positions computed from the on-board catalog. When the field has been identified, its position within the guiding imager field of view can be used to compute the pointing corrections necessary to point to a target of interest. In tracking mode, the software uses the past history to predict the quasi-periodic attitude control motions of the shuttle and sends pointing commands to cancel the motion and stabilize UVSTAR on the target. The guiding imager (guider) will have an 80-mm focal length and f/1.4 optics giving a field of view of 6 deg x 4.5 deg using a 385 x 288 pixel intensified CCD. It will be capable of providing high accuracy (better than 2 arc-sec) attitude determination from coarse (6 deg x 4.5 deg) initial knowledge of the pointing direction; and of pointing toward the target. It will also be capable of tracking at the same high accuracy with a processing time of less than a few hundredths of a second.

Laplacean Ideology for Preliminary Orbit Determination and Moving Celestial Body Identification in Virtual Epoch

NASA Astrophysics Data System (ADS)

Bykov, O. P.

Any CCD frames with stars or galaxies or clusters and other images must be studied for a searching of moving celestial objects, namely asteroids, comets, artificial Earth satellites inside them. At Pulkovo Astronomical Observatory, new methods and software were elaborated to solve this problem.

The numerical simulation tool for the MAORY multiconjugate adaptive optics system

NASA Astrophysics Data System (ADS)

Arcidiacono, C.; Schreiber, L.; Bregoli, G.; Diolaiti, E.; Foppiani, I.; Agapito, G.; Puglisi, A.; Xompero, M.; Oberti, S.; Cosentino, G.; Lombini, M.; Butler, R. C.; Ciliegi, P.; Cortecchia, F.; Patti, M.; Esposito, S.; Feautrier, P.

2016-07-01

The Multiconjugate Adaptive Optics RelaY (MAORY) is and Adaptive Optics module to be mounted on the ESO European-Extremely Large Telescope (E-ELT). It is an hybrid Natural and Laser Guide System that will perform the correction of the atmospheric turbulence volume above the telescope feeding the Multi-AO Imaging Camera for Deep Observations Near Infrared spectro-imager (MICADO). We developed an end-to-end Monte- Carlo adaptive optics simulation tool to investigate the performance of a the MAORY and the calibration, acquisition, operation strategies. MAORY will implement Multiconjugate Adaptive Optics combining Laser Guide Stars (LGS) and Natural Guide Stars (NGS) measurements. The simulation tool implement the various aspect of the MAORY in an end to end fashion. The code has been developed using IDL and use libraries in C++ and CUDA for efficiency improvements. Here we recall the code architecture, we describe the modeled instrument components and the control strategies implemented in the code.

Migration in the shearing sheet and estimates for young open cluster migration

NASA Astrophysics Data System (ADS)

Quillen, Alice C.; Nolting, Eric; Minchev, Ivan; De Silva, Gayandhi; Chiappini, Cristina

2018-04-01

Using tracer particles embedded in self-gravitating shearing sheet N-body simulations, we investigate the distance in guiding centre radius that stars or star clusters can migrate in a few orbital periods. The standard deviations of guiding centre distributions and maximum migration distances depend on the Toomre or critical wavelength and the contrast in mass surface density caused by spiral structure. Comparison between our simulations and estimated guiding radii for a few young supersolar metallicity open clusters, including NGC 6583, suggests that the contrast in mass surface density in the solar neighbourhood has standard deviation (in the surface density distribution) divided by mean of about 1/4 and larger than measured using COBE data by Drimmel and Spergel. Our estimate is consistent with a standard deviation of ˜0.07 dex in the metallicities measured from high-quality spectroscopic data for 38 young open clusters (<1 Gyr) with mean galactocentric radius 7-9 kpc.

[The Durkheim Test. Remarks on Susan Leigh Star's Boundary Objects].

PubMed

Gießmann, Sebastian

2015-09-01

The article reconstructs Susan Leigh Star's conceptual work on the notion of 'boundary objects'. It traces the emergence of the concept, beginning with her PhD thesis and its publication as Regions of the Mind in 1989. 'Boundary objects' attempt to represent the distributed, multifold nature of scientific work and its mediations between different 'social worlds'. Being addressed to several 'communities of practice', the term responded to questions from Distributed Artificial Intelligence in Computer Science, Workplace Studies and Computer Supported Cooperative Work (CSCW), and microhistorical approaches inside the growing Science and Technology Studies. Yet the interdisciplinary character and interpretive flexibility of Star’s invention has rarely been noticed as a conceptual tool for media theory. I therefore propose to reconsider Star's 'Durkheim test' for sociotechnical media practices.

Generative Models in Deep Learning: Constraints for Galaxy Evolution

NASA Astrophysics Data System (ADS)

Turp, Maximilian Dennis; Schawinski, Kevin; Zhang, Ce; Weigel, Anna K.

2018-01-01

New techniques are essential to make advances in the field of galaxy evolution. Recent developments in the field of artificial intelligence and machine learning have proven that these tools can be applied to problems far more complex than simple image recognition. We use these purely data driven approaches to investigate the process of star formation quenching. We show that Variational Autoencoders provide a powerful method to forward model the process of galaxy quenching. Our results imply that simple changes in specific star formation rate and bulge to disk ratio cannot fully describe the properties of the quenched population.

Atmospheric turbulence profiling with SLODAR using multiple adaptive optics wavefront sensors.

PubMed

Wang, Lianqi; Schöck, Matthias; Chanan, Gary

2008-04-10

The slope detection and ranging (SLODAR) method recovers atmospheric turbulence profiles from time averaged spatial cross correlations of wavefront slopes measured by Shack-Hartmann wavefront sensors. The Palomar multiple guide star unit (MGSU) was set up to test tomographic multiple guide star adaptive optics and provided an ideal test bed for SLODAR turbulence altitude profiling. We present the data reduction methods and SLODAR results from MGSU observations made in 2006. Wind profiling is also performed using delayed wavefront cross correlations along with SLODAR analysis. The wind profiling analysis is shown to improve the height resolution of the SLODAR method and in addition gives the wind velocities of the turbulent layers.

3D mapping of turbulence: a laboratory experiment

NASA Astrophysics Data System (ADS)

Le Louarn, Miska; Dainty, Christopher; Paterson, Carl; Tallon, Michel

2000-07-01

In this paper, we present the first experimental results of the 3D mapping method. 3D mapping of turbulence is a method to remove the cone effect with multiple laser guide stars and multiple deformable mirrors. A laboratory experiment was realized to verify the theoretical predictions. The setup consisted of two turbulent phase screens (made with liquid crystal devices) and a Shack-Hartmann wavefront sensor. We describe the interaction matrix involved in reconstructing Zernike commands for multiple deformable mirror from the slope measurements made from laser guide stars. It is shown that mirror commands can indeed be reconstructed with the 3D mapping method. Limiting factors of the method, brought to light by this experiment are discussed.

Carambola Cultivar, Fruit Ripeness, and Damage by Conspecific Larvae Influence the Host-Related Behaviors of Anastrepha obliqua (Diptera: Tephritidae).

PubMed

López-Ley, Jorge Ulises; Toledo, Jorge; Malo, Edi A; Gomez, Jaime; Santiesteban, Antonio; Rojas, Julio C

2016-02-01

In this study, we investigated the influence of cultivar type, fruit ripeness, and damage by conspecific larvae on the attraction of Anastrepha obliqua (Macquart) (Diptera: Tephritidae) to and oviposition on carambola fruit (Averroha carambola L.). The attraction of both sexes of A. obliqua to fruit of different quality was evaluated through cage experiments in the field, and the oviposition preferences of mated females were examined in laboratory tests. Both sexes, mated or virgin, were more attracted to the "Maha" fruit than to the "Golden Star" fruit, and the females oviposited more frequently on the Maha cultivar than the Golden Star cultivar. Both sexes were more attracted to ripe and half-ripe Maha fruits than to mature green fruit, and although females did not show a preference for ovipositing on half-ripe or ripe fruits, they did not oviposit on mature green fruits. Males did not show a preference for the volatiles from uninfested, artificially damaged, or infested Maha fruits, but females were more attracted to uninfested fruits than to artificially damaged and infested Maha fruits. Furthermore, females preferred to oviposit on uninfested fruits compared with artificially damaged fruit, and they did not oviposit on infested fruits. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The Kepler Catalog of Stellar Flares

NASA Astrophysics Data System (ADS)

Davenport, James R. A.

2016-09-01

A homogeneous search for stellar flares has been performed using every available Kepler light curve. An iterative light curve de-trending approach was used to filter out both astrophysical and systematic variability to detect flares. The flare recovery completeness has also been computed throughout each light curve using artificial flare injection tests, and the tools for this work have been made publicly available. The final sample contains 851,168 candidate flare events recovered above the 68% completeness threshold, which were detected from 4041 stars, or 1.9% of the stars in the Kepler database. The average flare energy detected is ˜1035 erg. The net fraction of flare stars increases with g - I color, or decreasing stellar mass. For stars in this sample with previously measured rotation periods, the total relative flare luminosity is compared to the Rossby number. A tentative detection of flare activity saturation for low-mass stars with rapid rotation below a Rossby number of ˜0.03 is found. A power-law decay in flare activity with Rossby number is found with a slope of -1, shallower than typical measurements for X-ray activity decay with Rossby number.

Rule based artificial intelligence expert system for determination of upper extremity impairment rating.

PubMed

Lim, I; Walkup, R K; Vannier, M W

1993-04-01

Quantitative evaluation of upper extremity impairment, a percentage rating most often determined using a rule based procedure, has been implemented on a personal computer using an artificial intelligence, rule-based expert system (AI system). In this study, the rules given in Chapter 3 of the AMA Guides to the Evaluation of Permanent Impairment (Third Edition) were used to develop such an AI system for the Apple Macintosh. The program applies the rules from the Guides in a consistent and systematic fashion. It is faster and less error-prone than the manual method, and the results have a higher degree of precision, since intermediate values are not truncated.

Detection technique for artificially illuminated objects in the outer solar system and beyond.

PubMed

Loeb, Abraham; Turner, Edwin L

2012-04-01

Existing and planned optical telescopes and surveys can detect artificially illuminated objects, comparable in total brightness to a major terrestrial city, at the outskirts of the Solar System. Orbital parameters of Kuiper belt objects (KBOs) are routinely measured to exquisite precisions of<10(-3). Here, we propose to measure the variation of the observed flux F from such objects as a function of their changing orbital distances D. Sunlight-illuminated objects will show a logarithmic slope α ≡ (d log F/d log D)=-4, whereas artificially illuminated objects should exhibit α=-2. The proposed Large Synoptic Survey Telescope (LSST) and other planned surveys will provide superb data and allow measurement of α for thousands of KBOs. If objects with α=-2 are found, follow-up observations could measure their spectra to determine whether they are illuminated by artificial lighting. The search can be extended beyond the Solar System with future generations of telescopes on the ground and in space that would have the capacity to detect phase modulation due to very strong artificial illumination on the nightside of planets as they orbit their parent stars.

Astronomy: Minds-on the Universe. Supplemental Teaching Activities for Grades K-8.

ERIC Educational Resources Information Center

Marble, Stephen; Fowler, Marilyn, Ed.

This teachers guide contains activities and materials created to teach astronomy concepts to children from grades K-8. It is organized into four units: (1) Earth and Stars; (2) Spheres and Orbits; (3) Stars and Gravity; and (4) Scales and Measurement. Activities are arranged within each unit around six content topics: (1) Earth; (2) Solar System;…

Five-Star Schools: Defining Quality in Early Childhood Programs

ERIC Educational Resources Information Center

Hertzog, Nancy B.

2012-01-01

Hakeem, Emily, Jose, and Latisha are all entering preschool in the fall. Their mothers are looking for the highest quality early childhood program they can find. Is there a guide for them to find a five-star program? Are all certified or accredited programs of equal quality? How do these parents and guardians know what defines quality in early…

Seeing in a New Light: Astro-1 Teacher's Guide with Activities.

ERIC Educational Resources Information Center

Essex Corp., Huntsville, AL.

For as long as people have walked the Earth, they have looked to the stars, have been inspired by their beauty and remoteness and have found their way over sea and deserts by their guidance. Since then, enormous progress has been made in the understanding of the stars, and today the expanding and fascinating world of high-energy astronomy awaits…

Student Measurements of Double Star STF 747AB

NASA Astrophysics Data System (ADS)

Bateman, Grace; Funk, Benjamin; Gillette, Travis; Rhoades, Breauna; Rhoades, Mark; Schlosser, Ruth; Sharpe, Scott; Thompson, Leone

2017-04-01

Data gathered from a 22-Inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece were used to measure the double star STF 747AB. Students from Apple Valley High School determined the separation to be 39.97 arc sec and the position angle to be 227.91 degrees. The students also used data from the digitized sky survey and determined a separation of 39.99 arc sec and a position angle of 225 degrees. The research was semi-independent from the Vanguard Double Star Workshop 2016 in Apple Valley, California.

How to Fabricate Functional Artificial Luciferases for Bioassays.

PubMed

Kim, Sung-Bae; Fujii, Rika

2016-01-01

The present protocol introduces fabrication of artificial luciferases (ALuc(®)) by extracting the consensus amino acids from the alignment of copepod luciferase sequences. The made ALucs have unique sequential identities that are phylogenetically distinctive from those of any existing copepod luciferase. Some ALucs exhibited heat stability, and strong and greatly prolonged optical intensities. The made ALucs are applicable to various bioassays as an optical readout, including live cell imaging, single-chain probes, and bioluminescent tags of antibodies. The present protocol guides on how to fabricate a unique artificial luciferase with designed optical properties and functionalities.

Thermal, Structural, and Optical Analysis of a Balloon-Based Imaging System

NASA Astrophysics Data System (ADS)

Borden, Michael; Lewis, Derek; Ochoa, Hared; Jones-Wilson, Laura; Susca, Sara; Porter, Michael; Massey, Richard; Clark, Paul; Netterfield, Barth

2017-03-01

The Subarcsecond Telescope And BaLloon Experiment, STABLE, is the fine stage of a guidance system for a high-altitude ballooning platform designed to demonstrate subarcsecond pointing stability over one minute using relatively dim guide stars in the visible spectrum. The STABLE system uses an attitude rate sensor and the motion of the guide star on a detector to control a Fast Steering Mirror to stabilize the image. The characteristics of the thermal-optical-mechanical elements in the system directly affect the quality of the point-spread function of the guide star on the detector, so a series of thermal, structural, and optical models were built to simulate system performance and ultimately inform the final pointing stability predictions. This paper describes the modeling techniques employed in each of these subsystems. The results from those models are discussed in detail, highlighting the development of the worst-case cold and hot cases, the optical metrics generated from the finite element model, and the expected STABLE residual wavefront error and decenter. Finally, the paper concludes with the predicted sensitivities in the STABLE system, which show that thermal deadbanding, structural pre-loading, and self-deflection under different loading conditions, and the speed of individual optical elements were particularly important to the resulting STABLE optical performance.

Navigating Space by the Stars

NASA Image and Video Library

2018-06-19

A tool that has helped guide sailors across oceans for centuries is now being tested aboard the International Space Station as a potential emergency navigation tool for guiding future spacecraft across the cosmos. The Sextant Navigation investigation tests use of a hand-held sextant aboard the space station. Sextants have a telescope-like optical sight to take precise angle measurements between pairs of stars from land or sea, enabling navigation without computer assistance. NASA’s Gemini missions conducted the first sextant sightings from a spacecraft, and designers built a sextant into Apollo vehicles as a navigation backup in the event the crew lost communications from their spacecraft. Jim Lovell demonstrated on Apollo 8 that sextant navigation could return a space vehicle home. Astronauts conducted additional sextant experiments on Skylab. Read more about the Sextant experiment happening aboard the space station: https://www.nasa.gov/mission_pages/station/research/news/Sextant_ISS HD Download: https://archive.org/details/jsc2018m000418_Navigating_Space_by_the_Stars

Navigating Space by the Stars - 16x9

NASA Image and Video Library

2018-06-18

A tool that has helped guide sailors across oceans for centuries is now being tested aboard the International Space Station as a potential emergency navigation tool for guiding future spacecraft across the cosmos. The Sextant Navigation investigation tests use of a hand-held sextant aboard the space station. Sextants have a telescope-like optical sight to take precise angle measurements between pairs of stars from land or sea, enabling navigation without computer assistance. NASA’s Gemini missions conducted the first sextant sightings from a spacecraft, and designers built a sextant into Apollo vehicles as a navigation backup in the event the crew lost communications from their spacecraft. Jim Lovell demonstrated on Apollo 8 that sextant navigation could return a space vehicle home. Astronauts conducted additional sextant experiments on Skylab. Read more about the Sextant experiment happening aboard the space station: https://www.nasa.gov/mission_pages/station/research/news/Sextant_ISS HD Download: https://archive.org/details/jsc2018m000418_Navigating_Space_by_the_Stars

The Gravity Probe B Experiment

NASA Technical Reports Server (NTRS)

Kolodziejczak, Jeffrey

2008-01-01

This presentation briefly describes the Gravity Probe B (GP-B) Experiment which is designed to measure parts of Einstein's general theory of relativity by monitoring gyroscope orientation relative to a distant guide star. To measure the miniscule angles predicted by Einstein's theory, it was necessary to build near-perfect gyroscopes that were approximately 50 million times more precise than the best navigational gyroscopes. A telescope mounted along the central axis of the dewar and spacecraft provided the experiment's pointing reference to a guide star. The telescope's image divide precisely split the star's beam into x-axis and y-axis components whose brightness could be compared. GP-B's 650-gallon dewar, kept the science instrument inside the probe at a cryogenic temperature for 17.3 months and also provided the thruster propellant for precision attitude and translation control. Built around the dewar, the GP-B spacecraft was a total-integrated system, comprising both the space vehicle and payload, dedicated as a single entity to experimentally testing predictions of Einstein's theory.

The vibration compensation system for ARGOS

NASA Astrophysics Data System (ADS)

Peter, D.; Gaessler, W.; Borelli, J.; Kulas, M.

2011-09-01

For every adaptive optics system telescope vibrations can strongly reduce the performance. This is true for the receiver part of the system i.e. the telescope and wave front sensor part as well as for the transmitter part in the case of a laser guide star system. Especially observations in deep fields observed with a laser guide star system without any tip-tilt star will be greatly spoiled by telescope vibrations. The ARGOS GLAO system actually being built for the LBT aims to implement this kind of mode where wave front correction will rely purely on signals from the laser beacons. To remove the vibrations from the uplink path a vibration compensation system will be installed. This system uses accelerometers to measure the vibrations and corrects their effect with a small fast tip-tilt mirror. The controller of the system is built based on the assumption that the vibrations take place at a few distinct frequencies. Here I present a lab set-up of this system and show first results of the performance.

New CO and HCN sources associated with IRAS carbon stars

NASA Technical Reports Server (NTRS)

NGUYEN-Q-RIEU; Epchtein, N.; TRUONG-BACH; Cohen, M.

1987-01-01

Emission of CO and HCN was detected in 22 out of a sample of 53 IRAS sources classified as unidentified carbon-rich objects. The sample was selected according to the presence of the silicon carbide feature as revealed by low-resolution spectra. The molecular line widths indicate that the CO and HCN emission arises from the circumstellar envelopes of very highly evolved stars undergoing mass loss. The visible stars tend to be deficient in CO as compared with unidentified sources. Most the detected CO and HCN IRAS stars are distinct and thick-shelled objects, but their infrared and CO luminosities are similar to those of IRC + 102156 AFGL and IRC-CO evolved stars. The 12 micron flux seems to be a good indicator of the distance, hence a guide for molecular searches.

Adaptive optics system for Cassegrain focus of SUBARU 8.2-m telescope

NASA Astrophysics Data System (ADS)

Takami, Hideki; Takato, Naruhisa; Otsubo, Masashi; Kanzawa, Tomio; Kamata, Yukiko; Nakashima, Koji; Iye, Masanori

1998-09-01

The adaptive optics system for Subaru 8.2m telescope of the National Astronomical Observatory Japan has been developed for the Cassegrain ear-IR instruments, CIAO and IRCS. The system consists of a wavefront curvature sensor with 36 subaperture photon-counting avalanche photodiode modules and a bimorph deformable mirror with 36 electrodes. The expected Strehl ratio at K band exceeds 0.4 for objects that are located close enough to a bright guide star as faint as R equals 16 mag at the median seeing of 0.45 arcsec at Mauna Kea. The system will be in operation in 1999 as a natural guide star system, and will eventually be upgraded to a laser guide star system in cooperating an IR wavefront tilt sensor to provide nearly full sky. The construction of this common use system to Subaru telescope is now underway in our laboratory in Tokyo. Prior to starting the fabrication of this common use system, a full size prototype system was constructed and tested with the 1.6 m IR telescope at our observatory in Tokyo. This system has the identical optical design, deformable mirror, loop control computer to those for the Subaru system, while the wavefront sensing detectors were less-sensitive analog APDs. We succeeded in getting closed loop images of stars in K band with diffraction limited core. The Strehl ratio was around 0.5 and the factor of improvement was about 20 at K-band under the average seeing of 2 arcsec during the observation. The loop sped of the system was 2 K corrections per second.

Principle-based ethics and nurses' attitudes towards artificial feeding.

PubMed

Day, L; Drought, T; Davis, A J

1995-02-01

Nurses often institute artificial feeding for patients who would otherwise starve. Recently, the courts in the United States have favoured withholding or withdrawing feedings from patients who currently refuse or previously gave some indication they would refuse artificial nutrition and hydration. This paper investigates under what circumstances nurses feel justified in withholding artificial nutrition and hydration. Structured interviews were conducted with 40 cancer care nurses from two sites, and 40 dementia care nurses from two sites. The interviews were based on two vignettes, one involving an alert patient with terminal cancer, the other a patient suffering end-stage Alzheimer's dementia, and were analysed for themes coinciding with principles of deontological ethics. Investigators found that autonomy, beneficence and non-maleficence most often guided nurses' decisions to withhold or implement artificial feeding.

Adaptive Optics for the Thirty Meter Telescope

NASA Astrophysics Data System (ADS)

Ellerbroek, Brent

2013-12-01

This paper provides an overview of the progress made since the last AO4ELT conference towards developing the first-light AO architecture for the Thirty Meter Telescope (TMT). The Preliminary Design of the facility AO system NFIRAOS has been concluded by the Herzberg Institute of Astrophysics. Work on the client Infrared Imaging Spectrograph (IRIS) has progressed in parallel, including a successful Conceptual Design Review and prototyping of On-Instrument WFS (OIWFS) hardware. Progress on the design for the Laser Guide Star Facility (LGSF) continues at the Institute of Optics and Electronics in Chengdu, China, including the final acceptance of the Conceptual Design and modest revisions for the updated TMT telescope structure. Design and prototyping activities continue for lasers, wavefront sensing detectors, detector readout electronics, real-time control (RTC) processors, and deformable mirrors (DMs) with their associated drive electronics. Highlights include development of a prototype sum frequency guide star laser at the Technical Institute of Physics and Chemistry (Beijing); fabrication/test of prototype natural- and laser-guide star wavefront sensor CCDs for NFIRAOS by MIT Lincoln Laboratory and W.M. Keck Observatory; a trade study of RTC control algorithms and processors, with prototyping of GPU and FPGA architectures by TMT and the Dominion Radio Astrophysical Observatory; and fabrication/test of a 6x60 actuator DM prototype by CILAS. Work with the University of British Columbia LIDAR is continuing, in collaboration with ESO, to measure the spatial/temporal variability of the sodium layer and characterize the sodium coupling efficiency of several guide star laser systems. AO performance budgets have been further detailed. Modeling topics receiving particular attention include performance vs. computational cost tradeoffs for RTC algorithms; optimizing performance of the tip/tilt, plate scale, and sodium focus tracking loops controlled by the NGS on-instrument wavefront sensors, sky coverage, PSF reconstruction for LGS MCAO, and precision astrometry for the galactic center and other observations.

Using Goal Interactions to Guide Planning: The Program Model.

DTIC Science & Technology

1987-04-01

8217.. ’:, :: ,:,: :... .-.. , .. *, -..,.,.. .. . . -. ’. ... -. ’. . -..: . . ... . .. ." 16 References [1] Berenji , H. R.; B. Khoshnevis. Use of Artificial Intelligence in Automated Process Planning

Hubble Space Telescope Fine Guidance Sensor and Two-Gyro Control Law Design, Implementation, and On-Orbit Performance. Part 3

NASA Technical Reports Server (NTRS)

Clapp, Brian R.

2005-01-01

For fifteen years, the science mission of the Hubble Space Telescope (HST) required using at least three rate gyros for n Controlling with alternate sensors to replace failing gyros can extend the HST science mission. A two-gyro control law has been designed and implemented using magnetometers, star trackers, and Fine Guidance Sensors (FGSs) to control vehicle rate about the missing gyro axis. The three aforementioned sensors are used in succession to reduce HST boresight jitter to less than 7 milli-arcseconds rms prior to science imaging. The Magnetometer and 2-Gyro (M2G) control law is used for large angle maneuvers and attitude control during earth. occultation of star trackers and FGSs. The Tracker and 2-Gyro (T2G) control law dampens M2G rates and controls attitude in preparation for guide star acquisition with the FGSs. The Fine Guidance Sensor and 2-Gyro (F2G) control law dampens T2G rates and controls HST attitude during science imaging. This paper describes the F2G control law. Details of F2G algorithms are presented, including computation of the FGS-measured star vector using non-linear equations, optimal estimation of HST body rate, design of the F2G control laws and gyro bias observer, SISO and MIMO linear stability analyses, and design of the F2G intramode transition and guide star acquisition logic. Results from an FGS flight spare ground test are presented that define acceptable HST jitter levels for successful guide star acquisition under two-gyro control. HST-specific disturbance and noise models are described that are based upon flight telemetry; these models are used in HSTSIM, a high-fidelity non-linear time domain simulation, to predict HST on-orbit disturbance responses and FGS interferometer Loss of Lock (LOL) characteristics under F2G control. Additional HSTSIM results are presented predicting HST quiescent boresight jitter performance, science maneuver performance, and observer configuration performance during F2G operation. Simulation results are compared to on-orbit data b m F2G flight tests performed in February 2005. Science images and point spread functions from the Advanced Camera for Surveys (ACS) High Resolution Camera (HRC) are presented that compare HST science performance under F2G versus three-gyro control. Images and flight telemetry show that HST boresight jitter with the new F2G control law is usually less than jitter using the three-gyro law, and HST boresight jitter during F2G operation is dependent upon guide star magnitude.

Nucleosynthesis in neutrino-driven, aspherical Population III supernovae

NASA Astrophysics Data System (ADS)

Fujimoto, Shin-ichiro; Hashimoto, Masa-aki; Ono, Masaomi; Kotake, Kei

2012-09-01

We investigate explosive nucleosynthesis during neutrino-driven, aspherical supernova (SN) explosion aided by standing accretion shock instability (SASI), based on two-dimensional hydrodynamic simulations of the explosion of 11, 15, 20, 25, 30 and 40M ⊙ stars with zero metallicity. The magnitude and asymmetry of the explosion energy are estimated with simulations, for a given set of neutrino luminosities and temperatures, not as in the previous study in which the explosion is manually and spherically initiated by means of a thermal bomb or a piston and also some artificial mixing procedures are applied for the estimate of abundances of the SN ejecta. By post-processing calculations with a large nuclear reaction network, we have evaluated abundances and masses of ejecta from the aspherical SNe. We find that matter mixing induced via SASI is important for the abundant production of nuclei with atomic number >= 21, in particular Sc, which is underproduced in the spherical models without artificial mixing. We also find that the IMF-averaged abundances are similar to those observed in extremely metal poor stars. However, observed [K/Fe] cannot be reproduced with our aspherical SN models.

Artificial ascites and pneumoperitoneum to facilitate thermal ablation of liver tumors: a pictorial essay.

PubMed

Bhagavatula, Sharath K; Chick, Jeffrey F B; Chauhan, Nikunj R; Shyn, Paul B

2017-02-01

Image-guided percutaneous thermal ablation is increasingly utilized in the treatment of hepatic malignancies. Peripherally located hepatic tumors can be difficult to access or located adjacent to critical structures that can be injured. As a result, ablation of peripheral tumors may be avoided or may be performed too cautiously, leading to inadequate ablation coverage. In these cases, separating the tumor from adjacent critical structures can increase the efficacy and safety of procedures. Artificial ascites and artificial pneumoperitoneum are techniques that utilize fluid and gas, respectively, to insulate critical structures from the thermal ablation zone. Induction of artificial ascites and artificial pneumoperitoneum can enable complete ablation of otherwise inaccessible hepatic tumors, improve tumor visualization, minimize unintended thermal injury to surrounding organs, and reduce post-procedural pain. This pictorial essay illustrates and discusses the proper technique and clinical considerations for successful artificial ascites and pneumoperitoneum creation to facilitate safe peripheral hepatic tumor ablation.

Radiative Feedback from Massive Stars as Traced by Multiband Imaging and Spectroscopic Mosaics

NASA Astrophysics Data System (ADS)

Berne, Olivier; Habart, Emilie; Peeters, Els; Abergel, A.; Bergin, E.; Bernard-Salas, J.; Bron, E.; Cami, J.; Cazaux, S.; Dartois, E.; Fuente, A.; Goicoechea, J.; Gordon, K.; Onaka, T.; Robberto, M.; Roellig, M.; Tielens, A.; Vincente, S.; Wolfire, M.; Okada, Y.

2017-11-01

Massive stars disrupt their natal molecular cloud material by dissociating molecules, ionizing atoms and molecules, and heating the gas and dust. These processes drive the evolution of interstellar matter in our Galaxy and throughout the Universe from the era of vigorous star formation at redshifts of 1-3, to the present day. Much of this interaction occurs in Photo-Dissociation Regions (PDRs) where far-ultraviolet photons of these stars create a largely neutral, but warm region of gas and dust. PDR emission dominates the IR spectra of star-forming galaxies and also provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, protoplanetary disk- and molecular cloud surfaces, globules, planetary nebulae, and starburst galaxies. We propose to provide template datasets designed to identify key PDR characteristics in JWST spectra in order to guide the preparation of Cycle 2 proposals on star-forming regions in our Galaxy and beyond. We plan to obtain the first spatially resolved, high spectral resolution IR observations of a PDR using NIRCam, NIRSpec, and MIRI. These data will test widely used theoretical models and extend them into the JWST era. We have engaged the broader community as exemplified by the supporting large international team of 138 scientists. We will assist the community interested in JWST observations of PDRs through science-enabling products that will guide observational planning and allow fast data analysis. We will train the community through telecons and dedicated workshops.

Thematic Journeys. I'll Never Draw a Perfect Star

ERIC Educational Resources Information Center

Zingher, Gary

2004-01-01

Children take enormous pride in their drawing abilities. They like bringing to life a specific object whether it is a star or a cat or a tree, and they will likely be frustrated until they can get it just right. Drawing is a way of thinking in motion, the brain guiding the hand, and it demonstrates strongly another type of intelligence. As a…

Realtime system for GLAS on WHT

NASA Astrophysics Data System (ADS)

Skvarč, Jure; Tulloch, Simon; Myers, Richard M.

2006-06-01

The new ground layer adaptive optics system (GLAS) on the William Herschel Telescope (WHT) on La Palma will be based on the existing natural guide star adaptive optics system called NAOMI. A part of the new developments is a new control system for the tip-tilt mirror. Instead of the existing system, built around a custom built multiprocessor computer made of C40 DSPs, this system uses an ordinary PC machine and a Linux operating system. It is equipped with a high sensitivity L3 CCD camera with effective readout noise of nearly zero. The software design for the tip-tilt system is being completely redeveloped, in order to make a use of object oriented design which should facilitate easier integration with the rest of the observing system at the WHT. The modular design of the system allows incorporation of different centroiding and loop control methods. To test the system off-sky, we have built a laboratory bench using an artificial light source and a tip-tilt mirror. We present results of tip-tilt correction quality using different centroiding algorithms and different control loop methods at different light levels. This system will serve as a testing ground for a transition to a completely PC-based real-time control system.

Kepler-90 System Compared to Our Solar System (Artist's Concept)

NASA Image and Video Library

2017-12-14

Our solar system now is tied for most number of planets around a single star, with the recent discovery of an eighth planet circling Kepler-90, a Sun-like star 2,545 light years from Earth. The planet was discovered in data from NASA's Kepler Space Telescope. This artist's concept depicts the Kepler-90 system compared with our own solar system. The newly-discovered Kepler-90i -- a sizzling hot, rocky planet that orbits its star once every 14.4 days -- was found using machine learning from Google. Machine learning is an approach to artificial intelligence in which computers "learn." In this case, computers learned to identify planets by finding in Kepler data instances where the telescope recorded changes in starlight caused by planets beyond our solar system, known as exoplanets. https://photojournal.jpl.nasa.gov/catalog/PIA22193

Improving the Ability of Image Sensors to Detect Faint Stars and Moving Objects Using Image Deconvolution Techniques

PubMed Central

Fors, Octavi; Núñez, Jorge; Otazu, Xavier; Prades, Albert; Cardinal, Robert D.

2010-01-01

In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors. PMID:22294896

Improving the ability of image sensors to detect faint stars and moving objects using image deconvolution techniques.

PubMed

Fors, Octavi; Núñez, Jorge; Otazu, Xavier; Prades, Albert; Cardinal, Robert D

2010-01-01

In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors.

Complexity, Heuristic, and Search Analysis for the Games of Crossings and Epaminondas

DTIC Science & Technology

2014-03-27

research in Artifical Intelligence (Section 2.1) and why games are studied (Section 2.2). Section 2.3 discusses how games are played and solved. An...5 2.1 Games in Artificial Intelligence . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Game Study...Artificial Intelligence UCT Upper Confidence Bounds applied to Trees HUCT Heuristic Guided UCT LOA Lines of Action UCB Upper Confidence Bound RAVE Rapid

The architecture challenge: Future artificial-intelligence systems will require sophisticated architectures, and knowledge of the brain might guide their construction.

PubMed

Baldassarre, Gianluca; Santucci, Vieri Giuliano; Cartoni, Emilio; Caligiore, Daniele

2017-01-01

In this commentary, we highlight a crucial challenge posed by the proposal of Lake et al. to introduce key elements of human cognition into deep neural networks and future artificial-intelligence systems: the need to design effective sophisticated architectures. We propose that looking at the brain is an important means of facing this great challenge.

A search for Earth-crossing asteroids, supplement

NASA Technical Reports Server (NTRS)

Taff, L. G.; Sorvari, J. M.; Kostishack, D. F.

1984-01-01

The ground based electro-optical deep space surveillance program involves a network of computer controlled 40 inch 1m telescopes equipped with large format, low light level, television cameras of the intensified silicon diode array type which is to replace the Baker-Nunn photographic camera system for artificial satellite tracking. A prototype observatory was constructed where distant artificial satellites are discriminated from stars in real time on the basis of the satellites' proper motion. Hardware was modified and the technique was used to observe and search for minor planets. Asteroids are now routinely observed and searched. The complete observing cycle, including the 2"-3" measurement of position, requires about four minutes at present. The commonality of asteroids and artificial satellite observing, searching, data reduction, and orbital analysis is stressed. Improvements to the hardware and software as well as operational techniques are considered.

Look to the Sky. An All-Purpose Interdisciplinary Guide to Astronomy. Grades 4-12.

ERIC Educational Resources Information Center

DeBruin, Jerry; Murad, Don

This guide features materials and activities about stars for integration into other academic disciplines. Part one describes how to begin to look to the sky, including usage of the camera, binoculars, and telescope. Part two, "Keep Up to Date," introduces information on resource materials, such as astronomy books, magazines, newsletters,…

They Snooze, You Lose: The Educator's Guide to Successful Presentations

ERIC Educational Resources Information Center

Burmark, Lynell

2011-01-01

In today's increasingly visual world, the art of giving presentations is a much-needed talent. "They Snooze, You Lose", provides a comprehensive guide made especially for teachers and administrators who want to become presentation "stars" in their classrooms, at board meetings, or any time they are in front of an audience. This book describes how…

ARTIFICIAL LIGHTING FOR MODERN SCHOOLS, A GUIDE FOR ADMINISTRATIVE USE.

ERIC Educational Resources Information Center

REIDA, GEORGE W.; AND OTHERS

THE DEVELOPMENT OF GOOD VISUAL ENVIRONMENT AND ECONOMICALLY FEASIBLE LIGHTING INSTALLATIONS IN SCHOOLS IS DISCUSSED IN THIS GUIDE. EIGHTY PERCENT OF ALL SCHOOL LEARNING IS GAINED THROUGH THE EYES AS ESTIMATED BY THE U.S. OFFICE OF EDUCATION. GOOD SCHOOL LIGHTING IS COMFORTABLE, GLAREFREE AND ADEQUATE FOR THE VISUAL TASK. EYE STRAIN AND UNNECESSARY…

The Gemini-South MCAO operational model: insights on a new era of telescope operation

NASA Astrophysics Data System (ADS)

Trancho, Gelys; Bec, Matthieu; Artigau, Etienne; d'Orgeville, Celine; Gratadour, Damien; Rigaut, Francois J.; Walls, Brian

2008-07-01

The Gemini Observatory is implementing a Multi-Conjugate Adaptive Optics (MCAO) system as a facility instrument for the Gemini South telescope (GeMS). The system will include 5 Laser Guide Stars, 3 Natural Guide Stars, and 3 deformable mirrors, optically conjugated at different altitudes, to achieve near-uniform atmospheric compensation over a one arc minute square field of view. This setup implies some level of operational complexity. In this paper we describe how GeMS will be integrated into the flow of Gemini operations, from the observing procedures necessary to execute the programs in the queue (telescope control software, observing tools, sequence executor) to the safety implementation needed such as spotters/ASCAM, space command and laser traffic control software.

HYDROGEL-BASED NANOCOMPOSITES OF THERAPEUTIC PROTEINS FOR TISSUE REPAIR

PubMed Central

Zhu, Suwei; Segura, Tatiana

2014-01-01

The ability to design artificial extracellular matrices as cell instructive scaffolds has opened the door to technologies capable of studying cell fates in vitro and to guide tissue repair in vivo. One main component of the design of artificial extracellular matrices is the incorporation of protein-based biochemical cues to guide cell phenotypes and multicellular organizations. However, promoting the long-term bioactivity, controlling the bioavailability and understanding how the physical presentations of these proteins impacts cellular fates are among the challenges of the field. Nanotechnolgy has advanced to meet the challenges of protein therapeutics. For example, the approaches to incorporating proteins into tissue repairing scaffolds have ranged from bulk encapsulations to smart nanodepots that protect proteins from degradations and allow opportunities for controlled release. PMID:24778979

HYDROGEL-BASED NANOCOMPOSITES OF THERAPEUTIC PROTEINS FOR TISSUE REPAIR.

PubMed

Zhu, Suwei; Segura, Tatiana

2014-05-01

The ability to design artificial extracellular matrices as cell instructive scaffolds has opened the door to technologies capable of studying cell fates in vitro and to guide tissue repair in vivo . One main component of the design of artificial extracellular matrices is the incorporation of protein-based biochemical cues to guide cell phenotypes and multicellular organizations. However, promoting the long-term bioactivity, controlling the bioavailability and understanding how the physical presentations of these proteins impacts cellular fates are among the challenges of the field. Nanotechnolgy has advanced to meet the challenges of protein therapeutics. For example, the approaches to incorporating proteins into tissue repairing scaffolds have ranged from bulk encapsulations to smart nanodepots that protect proteins from degradations and allow opportunities for controlled release.

VizieR Online Data Catalog: OGLE eclipsing binaries in LMC (Wyrzykowski+, 2003)

NASA Astrophysics Data System (ADS)

Wyrzykowski, L.; Udalski, A.; Kubiak, M.; Szymanski, M.; Zebrun, K.; Soszynski, I.; Wozniak, P. R.; Pietrzynski, G.; Szewczyk, O.

2003-09-01

We present the catalog of 2580 eclipsing binary stars detected in 4.6 square degree area of the central parts of the Large Magellanic Cloud. The photometric data were collected during the second phase of the OGLE microlensing search from 1997 to 2000. The eclipsing objects were selected with the automatic search algorithm based on an artificial neural network. Basic statistics of eclipsing stars are presented. Also, the list of 36 candidates of detached eclipsing binaries for spectroscopic study and for precise LMC distance determination is provided. The full catalog is accessible from the OGLE Internet archive. (2 data files).

Chitosan-film enhanced chitosan nerve guides for long-distance regeneration of peripheral nerves.

PubMed

Meyer, Cora; Stenberg, Lena; Gonzalez-Perez, Francisco; Wrobel, Sandra; Ronchi, Giulia; Udina, Esther; Suganuma, Seigo; Geuna, Stefano; Navarro, Xavier; Dahlin, Lars B; Grothe, Claudia; Haastert-Talini, Kirsten

2016-01-01

Biosynthetic nerve grafts are developed in order to complement or replace autologous nerve grafts for peripheral nerve reconstruction. Artificial nerve guides currently approved for clinical use are not widely applied in reconstructive surgery as they still have limitations especially when it comes to critical distance repair. Here we report a comprehensive analysis of fine-tuned chitosan nerve guides (CNGs) enhanced by introduction of a longitudinal chitosan film to reconstruct critical length 15 mm sciatic nerve defects in adult healthy Wistar or diabetic Goto-Kakizaki rats. Short and long term investigations demonstrated that the CNGs enhanced by the guiding structure of the introduced chitosan film significantly improved functional and morphological results of nerve regeneration in comparison to simple hollow CNGs. Importantly, this was detectable both in healthy and in diabetic rats (short term) and the regeneration outcome almost reached the outcome after autologous nerve grafting (long term). Hollow CNGs provide properties likely leading to a wider clinical acceptance than other artificial nerve guides and their performance can be increased by simple introduction of a chitosan film with the same advantageous properties. Therefore, the chitosan film enhanced CNGs represent a new generation medical device for peripheral nerve reconstruction. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Nano-JASMINE: Simulation of Data Outputs

NASA Astrophysics Data System (ADS)

Kobayashi, Y.; Yano, T.; Hatsutori, Y.; Gouda, N.; Murooka, J.; Niwa, Y.; Yamada, Y.

We simulated the data outputs of the first Japanese astrometry satellite Nano-JASMINE, which is scheduled to be launched by the Cyclone-4 rocket in August 2011. The simulations were carried out using existing stellar catalogues such as the Hipparcos catalogue, the Tycho catalogue, and the Guide Star catalogue version 2.3. Several statics are shown such as the number of stars those will be measured distances using annual aberration observations. The method for determining the initial direction of the satellite's spin axis has also been discussed. In this case, the frequency of bright stars observed by the satellite is an important factor.

Detection Technique for Artificially Illuminated Objects in the Outer Solar System and Beyond

PubMed Central

Loeb, Abraham

2012-01-01

Abstract Existing and planned optical telescopes and surveys can detect artificially illuminated objects, comparable in total brightness to a major terrestrial city, at the outskirts of the Solar System. Orbital parameters of Kuiper belt objects (KBOs) are routinely measured to exquisite precisions of<10−3. Here, we propose to measure the variation of the observed flux F from such objects as a function of their changing orbital distances D. Sunlight-illuminated objects will show a logarithmic slope α ≡ (d log F/d log D)=−4, whereas artificially illuminated objects should exhibit α=−2. The proposed Large Synoptic Survey Telescope (LSST) and other planned surveys will provide superb data and allow measurement of α for thousands of KBOs. If objects with α=−2 are found, follow-up observations could measure their spectra to determine whether they are illuminated by artificial lighting. The search can be extended beyond the Solar System with future generations of telescopes on the ground and in space that would have the capacity to detect phase modulation due to very strong artificial illumination on the nightside of planets as they orbit their parent stars. Key Words: Astrobiology—SETI—Kuiper belt objects—Artificial illumination. Astrobiology 12, 290–294. PMID:22490065

Design of pre-optics for laser guide star wavefront sensor for the ELT

NASA Astrophysics Data System (ADS)

Muslimov, Eduard; Dohlen, Kjetil; Neichel, Benoit; Hugot, Emmanuel

2017-12-01

In the present paper, we consider the optical design of a zoom system for the active refocusing in laser guide star wavefront sensors. The system is designed according to the specifications coming from the Extremely Large Telescope (ELT)-HARMONI instrument, the first-light, integral field spectrograph for the European (E)-ELT. The system must provide a refocusing of the laser guide as a function of telescope pointing and large decentring of the incoming beam. The system considers four moving lens groups, each of them being a doublet with one aspherical surface. The advantages and shortcomings of such a solution in terms of the component displacements and complexity of the surfaces are described in detail. It is shown that the system can provide the median value of the residual wavefront error of 13.8-94.3 nm and the maximum value <206 nm, while the exit pupil distortion is 0.26-0.36% for each of the telescope pointing directions.

The Universal Book of Astronomy: From the Andromeda Galaxy to the Zone of Avoidance

NASA Astrophysics Data System (ADS)

Darling, David

2003-10-01

The ultimate guide to the final frontier This alphabetical tour of the universe provides all the history, science, and up-to-the-minute facts needed to explore the skies with authority. Packed with more than 3,000 entries that cover everything from major observatories and space telescopes to biographies of astronomers throughout the ages, it showcases an extraordinary array of newfound wonders, including microquasars, brown dwarfs, and dark energy, as well as a host of individual comets, asteroids, moons, planets, stars, nebulas, and galaxies. Featuring nearly 200 illustrations and eight pages of color photographs, this comprehensive guide provides easy lookup of topics and offers more in-depth information than can be found in existing star guides or astronomy dictionaries. It's an ideal resource for the amateur astronomer or anyone with an interest in the mysteries of the cosmos. David Darling, PhD (Brainerd, MN), is the author of The Complete Book of Spaceflight (0-471-05649-9) and Equations of Eternity, a New York Times Notable Book.

Actively targeted delivery of anticancer drug to tumor cells by redox-responsive star-shaped micelles.

PubMed

Shi, Chunli; Guo, Xing; Qu, Qianqian; Tang, Zhaomin; Wang, Yi; Zhou, Shaobing

2014-10-01

In cancer therapy nanocargos based on star-shaped polymer exhibit unique features such as better stability, smaller size distribution and higher drug capacity in comparison to linear polymeric micelles. In this study, we developed a multifunctional star-shaped micellar system by combination of active targeting ability and redox-responsive behavior. The star-shaped micelles with good stability were self-assembled from four-arm poly(ε-caprolactone)-poly(ethylene glycol) copolymer. The redox-responsive behaviors of these micelles triggered by glutathione were evaluated from the changes of micellar size, morphology and molecular weight. In vitro drug release profiles exhibited that in a stimulated normal physiological environment, the redox-responsive star-shaped micelles could maintain good stability, whereas in a reducing and acid environment similar with that of tumor cells, the encapsulated agent was promptly released. In vitro cellular uptake and subcellular localization of these micelles were further studied with confocal laser scanning microscopy and flow cytometry against the human cervical cancer cell line HeLa. In vivo and ex vivo DOX fluorescence imaging displayed that these FA-functionalized star-shaped micelles possessed much better specificity to target solid tumor. Both the qualitative and quantitative results of the antitumor effect in 4T1 tumor-bearing BALB/c mice demonstrated that these redox-responsive star-shaped micelles have a high therapeutic efficiency to artificial solid tumor. Therefore, the multifunctional star-shaped micelles are a potential platform for targeted anticancer drug delivery. Copyright © 2014 Elsevier Ltd. All rights reserved.

The impact of interpretive and reductive front-of-pack labels on food choice and willingness to pay.

PubMed

Talati, Zenobia; Norman, Richard; Pettigrew, Simone; Neal, Bruce; Kelly, Bridget; Dixon, Helen; Ball, Kylie; Miller, Caroline; Shilton, Trevor

2017-12-19

This study examined how front-of-pack labels and product healthfulness affect choice and willingness to pay across a range of foods. It was hypothesized that: (i) product choice and (ii) willingness to pay would be more aligned with product healthfulness when healthfulness was expressed through the Health Star Rating, followed by the Multiple Traffic Light, then the Daily Intake Guide, and (iii) the Nutrition Facts Panel would be viewed infrequently. Adults and children aged 10+ years (n = 2069) completed an online discrete choice task involving mock food packages. A 4 food type (cookies, corn flakes, pizza, yoghurt) × 2 front-of-pack label presence (present, absent) × 3 front-of-pack label type (Daily Intake Guide, Multiple Traffic Light, Health Star Rating) × 3 price (cheap, moderate, expensive) × 3 healthfulness (less healthy, moderately healthy, healthier) design was used. A 30 s time limit was imposed for each choice. Of the three front-of-pack labels tested, the Health Star Rating produced the largest differences in choices, with 40% (95% CIs: 38%-42%) of respondents selecting the healthier variant, 33% selecting the moderately healthy variant (95% CIs: 31%-35%), and 23% (95% CIs: 21%-24%) selecting the less healthy variant of the four products included in the study. The Multiple Traffic Light led to significant differences in choices between healthier (35%, 95% CIs: 33%-37%) and less healthy products (29%, 95% CIs: 27%-31%), but not moderately healthy products (32%, 95% CIs: 30%-34%). No significant differences in choices were observed by product healthfulness when the Daily Intake Guide was present. Only the Health Star Rating resulted in a significantly greater willingness to pay for healthier versus less healthy products. The Nutrition Facts Panel was viewed for only 7% of all mock packages. Front-of-pack labels that are more interpretive, such as the Health Star Rating, can be more effective at directing consumers towards healthier choices than reductive front-of-pack labels such as the Daily Intake Guide. The study results provide policy makers with clear guidance on the types of front-of-pack labels that are most likely to achieve positive health outcomes at a population level.

Analysis of fratricide effect observed with GeMS and its relevance for large aperture astronomical telescopes

NASA Astrophysics Data System (ADS)

Otarola, Angel; Neichel, Benoit; Wang, Lianqi; Boyer, Corinne; Ellerbroek, Brent; Rigaut, François

2013-12-01

Large aperture ground-based telescopes require Adaptive Optics (AO) to correct for the distortions induced by atmospheric turbulence and achieve diffraction limited imaging quality. These AO systems rely on Natural and Laser Guide Stars (NGS and LGS) to provide the information required to measure the wavefront from the astronomical sources under observation. In particular one such LGS method consists in creating an artificial star by means of fluorescence of the sodium atoms at the altitude of the Earth's mesosphere. This is achieved by propagating one or more lasers, at the wavelength of the Na D2a resonance, from the telescope up to the mesosphere. Lasers can be launched from either behind the secondary mirror or from the perimeter of the main aperture. The so-called central- and side-launch systems, respectively. The central-launch system, while helpful to reduce the LGS spot elongation, introduces the so-called "fratricide" effect. This consists of an increase in the photon-noise in the AO Wave Front Sensors (WFS) sub-apertures, with photons that are the result of laser photons back-scattering from atmospheric molecules (Rayleigh scattering) and atmospheric aerosols (dust and/or cirrus clouds ice particles). This affects the performance of the algorithms intended to compute the LGS centroids and subsequently compute and correct the turbulence-induced wavefront distortions. In the frame of the Thirty Meter Telescope (TMT) project and using actual LGS WFS data obtained with the Gemini Multi-Conjugate Adaptive Optics System (Gemini MCAO a.k.a. GeMS), we show results from an analysis of the temporal variability of the observed fratricide effect, as well as comparison of the absolute magnitude of fratricide photon-flux level with simulations using models that account for molecular (Rayleigh) scattering and photons backscattered from cirrus clouds.

The Performance of the Robo-AO Laser Guide Star Adaptive Optics System at the Kitt Peak 2.1 m Telescope

NASA Astrophysics Data System (ADS)

Jensen-Clem, Rebecca; Duev, Dmitry A.; Riddle, Reed; Salama, Maïssa; Baranec, Christoph; Law, Nicholas M.; Kulkarni, S. R.; Ramprakash, A. N.

2018-01-01

Robo-AO is an autonomous laser guide star adaptive optics (AO) system recently commissioned at the Kitt Peak 2.1 m telescope. With the ability to observe every clear night, Robo-AO at the 2.1 m telescope is the first dedicated AO observatory. This paper presents the imaging performance of the AO system in its first 18 months of operations. For a median seeing value of 1.″44, the average Strehl ratio is 4% in the i\\prime band. After post processing, the contrast ratio under sub-arcsecond seeing for a 2≤slant i\\prime ≤slant 16 primary star is five and seven magnitudes at radial offsets of 0.″5 and 1.″0, respectively. The data processing and archiving pipelines run automatically at the end of each night. The first stage of the processing pipeline shifts and adds the rapid frame rate data using techniques optimized for different signal-to-noise ratios. The second “high-contrast” stage of the pipeline is eponymously well suited to finding faint stellar companions. Currently, a range of scientific programs, including the synthetic tracking of near-Earth asteroids, the binarity of stars in young clusters, and weather on solar system planets are being undertaken with Robo-AO.

Autonomous development and learning in artificial intelligence and robotics: Scaling up deep learning to human-like learning.

PubMed

Oudeyer, Pierre-Yves

2017-01-01

Autonomous lifelong development and learning are fundamental capabilities of humans, differentiating them from current deep learning systems. However, other branches of artificial intelligence have designed crucial ingredients towards autonomous learning: curiosity and intrinsic motivation, social learning and natural interaction with peers, and embodiment. These mechanisms guide exploration and autonomous choice of goals, and integrating them with deep learning opens stimulating perspectives.

Application of wavefield imaging to characterize scattering from artificial and impact damage in composite laminate panels

NASA Astrophysics Data System (ADS)

Williams, Westin B.; Michaels, Thomas E.; Michaels, Jennifer E.

2018-04-01

Composite materials used for aerospace applications are highly susceptible to impacts, which can result in barely visible delaminations. Reliable and fast detection of such damage is needed before structural failures occur. One approach is to use ultrasonic guided waves generated from a sparse array consisting of permanently mounted or embedded transducers for performing structural health monitoring. This array can detect introduction of damage after baseline subtraction, and also provide localization and characterization information via the minimum variance imaging algorithm. Imaging performance can vary considerably depending upon where damage is located with respect to the array; however, prior work has shown that knowledge of expected scattering can improve imaging consistency for artificial damage at various locations. In this study, anisotropic material attenuation and wave speed are estimated as a function of propagation angle using wavefield data recorded along radial lines at multiple angles with respect to an omnidirectional guided wave source. Additionally, full wavefield data are recorded before and after the introduction of artificial and impact damage so that wavefield baseline subtraction may be applied. 3-D filtering techniques are then used to reduce noise and isolate scattered waves. A model for estimating scattering of a circular defect is developed and scattering estimates for both artificial and impact damage are presented and compared.

Hybrid Architecture Active Wavefront Sensing and Control

NASA Technical Reports Server (NTRS)

Feinberg, Lee; Dean, Bruce; Hyde, Tupper

2010-01-01

A method was developed for performing relatively high-speed wavefront sensing and control to overcome thermal instabilities in a segmented primary mirror telescope [e.g., James Webb Space Telescope (JWST) at L2], by using the onboard fine guidance sensor (FGS) to minimize expense and complexity. This FGS performs centroiding on a bright star to feed the information to the pointing and control system. The proposed concept is to beam split the image of the guide star (or use a single defocused guide star image) to perform wavefront sensing using phase retrieval techniques. Using the fine guidance sensor star image for guiding and fine phasing eliminates the need for other, more complex ways of achieving very accurate sensing and control that is needed for UV-optical applications. The phase retrieval occurs nearly constantly, so passive thermal stability over fourteen days is not required. Using the FGS as the sensor, one can feed segment update information to actuators on the primary mirror that can update the primary mirror segment fine phasing with this frequency. Because the thermal time constants of the primary mirror are very slow compared to this duration, the mirror will appear extremely stable during observations (to the level of accuracy of the sensing and control). The sensing can use the same phase retrieval techniques as the JWST by employing an additional beam splitter, and having each channel go through a weak lens (one positive and one negative). The channels can use common or separate detectors. Phase retrieval can be performed onboard. The actuation scheme would include a coarse stage able to achieve initial alignment of several millimeters of range (similar to JWST and can use a JWST heritage sensing approach in the science camera) and a fine stage capable of continual updates.

A Cluster Of Activities On Coma From The Hubble Space Telescope, StarDate, And McDonald Observatory

NASA Astrophysics Data System (ADS)

Hemenway, Mary Kay; Jogee, S.; Fricke, K.; Preston, S.

2011-01-01

With a goal of providing a vast audience of students, teachers, the general public, and Spanish-speakers with activities to learn about research on the Coma cluster of galaxies based on the HST ACS Treasury survey of Coma, McDonald Observatory used a many-faceted approach. Since this research offered an unprecedented legacy dataset, part of the challenge was to convey the importance of this project to a diverse audience. The methodology was to create different products for different (overlapping) audiences. Five radio programs were produced in English and Spanish for distribution on over 500 radio stations in the US and Mexico with a listening audience of over 2 million; in addition to the radio listeners, there were over 13,000 downloads of the English scripts and almost 6000 of the Spanish. Images were prepared for use in the StarDate Online Astronomy Picture of the Week, for ViewSpace (used in museums), and for the StarDate/Universo Teacher Guide. A high-school level activity on the Coma Cluster was prepared and distributed both on-line and in an upgraded printed version of the StarDate/Universo Teacher Guide. This guide has been distributed to over 1700 teachers nationally. A YouTube video about careers and research in astronomy using the Coma cluster as an example was produced. Just as the activities were varied, so were the evaluation methods. This material is based upon work supported by the National Aeronautics and Space Administration under Grant/Contract/Agreement No. HST-EO-10861.35-A issued through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-main Sequence Stars

NASA Astrophysics Data System (ADS)

Lim, Beomdu; Sung, Hwankyung; Kim, Jinyoung S.; Bessell, Michael S.; Hwang, Narae; Park, Byeong-Gon

2016-11-01

The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were considered to be a result of a real spread in age, the corresponding cluster formation timescale would be about 5-20 Myr. Hence it could be interpreted that star formation in an open cluster is prolonged for up to a few tens of Myr. However, difficulties in reddening correction, observational errors, and systematic uncertainties introduced by imperfect evolutionary models for PMS stars can result in an artificial age spread. Alternatively, we can utilize Li abundance as a relative age indicator of PMS star to determine the cluster formation timescale. The optical spectra of 134 PMS stars in NGC 2264 have been obtained with MMT/Hectochelle. The equivalent widths have been measured for 86 PMS stars with a detectable Li line (3500\\lt {T}{eff}[{{K}}]≤slant 6500). Li abundance under the condition of local thermodynamic equilibrium (LTE) was derived using the conventional curve of growth method. After correction for non-LTE effects, we find that the initial Li abundance of NGC 2264 is A({Li})=3.2+/- 0.2. From the distribution of the Li abundances, the underlying age spread of the visible PMS stars is estimated to be about 3-4 Myr and this, together with the presence of embedded populations in NGC 2264, suggests that the cluster formed on a timescale shorter than 5 Myr.

Optics: Light, Color, and Their Uses. An Educator's Guide with Activities in Science and Mathematics.

ERIC Educational Resources Information Center

National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

This educator's guide from discusses optics, light, color and their uses. Activities include: (1) "Reflection of Light with a Plane (Flat) Mirror--Trace a Star"; (2) "Reflection of Light with Two Plane Mirrors--Double Mirrors Placed at a 90-Degree Angle"; (3) "Reflection of Light with Two Plane Mirrors--Double Mirrors Placed at a Number of…

Resource Handbook--Space Beyond the Earth. A Supplement to Basic Curriculum Guide--Science, Grades K-6.

ERIC Educational Resources Information Center

Starr, John W., 3rd., Ed.

GRADES OR AGES: Grades K-6. SUBJECT MATTER: Science; space. ORGANIZATION AND PHYSICAL APPEARANCE: The guide is divided into four units: 1) the sun, earth, and moon; 2) stars and planets; 3) exploring space; 4) man's existence in space. Each unit includes initiatory and developmental activities. There are also sections on evaluation, vocabulary,…

Status of ARGOS - The Laser Guide Star System for the LBT

NASA Astrophysics Data System (ADS)

Raab, Walfried; Rabien, Sebastian; Gaessler, Wolfgang; Esposito, Simone; Antichi, Jacopo; Lloyd-Hart, Michael; Barl, Lothar; Beckmann, Udo; Bonaglia, Marco; Borelli, Jose; Brynnel, Joar; Buschkamp, Peter; Busoni, Lorenzo; Carbonaro, Luca; Christou, Julian; Connot, Claus; Davies, Richard; Deysenroth, Matthias; Durney, Olivier; Green, Richard; Gemperlein, Hans; Gasho, Victor; Haug, Marcus; Hubbard, Pete; Ihle, Sebastian; Kulas, Martin; Loose, Christina; Lehmitz, Michael; Noenickx, Jamison; Nussbaum, Edmund; Orban De Xivry, Gilles; Quirrenbach, Andreas; Peter, Diethard; Rahmer, Gustavo; Rademacher, Matt; Storm, Jesper; Schwab, Christian; Vaitheeswaran, Vidhya; Ziegleder, Julian

2013-12-01

ARGOS is an innovative multiple laser guide star adaptive optics system for the Large Binocular Telescope (LBT), designed to perform effective GLAO correction over a very wide field of view. The system is using high powered pulsed green (532 nm) lasers to generate a set of three guide stars above each of the LBT mirrors. The laser beams are launched through a 40 cm telescope and focused at an altitude of 12 km, creating laser beacons by means of Rayleigh scattering. The returning scattered light, primarily sensitive to the turbulences close to the ground, is detected by a gated wavefront sensor system. The derived ground layer correction signals are directly driving the adaptive secondary mirror of the LBT. ARGOS is especially designed for operation with the multiple object spectrograph Luci, which will benefit from both, the improved spatial resolution, as well as the strongly enhanced flux. In addition to the GLAO Rayleigh beacon system, ARGOS was also designed for a possible future upgrade with a hybrid sodium laser - Rayleigh beacon combination, enabling diffraction limited operation. The ARGOS laser system has undergone extensive tests during Summer 2012 and is scheduled for installation at the LBT in Spring 2013. The remaining sub-systems will be installed during the course of 2013. We report on the overall status of the ARGOS system and the results of the sub-system characterizations carried out so far.

Citizen Science Provides Valuable Data for Monitoring Global Night Sky Luminance

PubMed Central

Kyba, Christopher C. M.; Wagner, Janna M.; Kuechly, Helga U.; Walker, Constance E.; Elvidge, Christopher D.; Falchi, Fabio; Ruhtz, Thomas; Fischer, Jürgen; Hölker, Franz

2013-01-01

The skyglow produced by artificial lights at night is one of the most dramatic anthropogenic modifications of Earth's biosphere. The GLOBE at Night citizen science project allows individual observers to quantify skyglow using star maps showing different levels of light pollution. We show that aggregated GLOBE at Night data depend strongly on artificial skyglow, and could be used to track lighting changes worldwide. Naked eye time series can be expected to be very stable, due to the slow pace of human eye evolution. The standard deviation of an individual GLOBE at Night observation is found to be 1.2 stellar magnitudes. Zenith skyglow estimates from the “First World Atlas of Artificial Night Sky Brightness” are tested using a subset of the GLOBE at Night data. Although we find the World Atlas overestimates sky brightness in the very center of large cities, its predictions for Milky Way visibility are accurate. PMID:23677222

Research of centroiding algorithms for extended and elongated spot of sodium laser guide star

NASA Astrophysics Data System (ADS)

Shao, Yayun; Zhang, Yudong; Wei, Kai

2016-10-01

Laser guide stars (LGSs) increase the sky coverage of astronomical adaptive optics systems. But spot array obtained by Shack-Hartmann wave front sensors (WFSs) turns extended and elongated, due to the thickness and size limitation of sodium LGS, which affects the accuracy of the wave front reconstruction algorithm. In this paper, we compared three different centroiding algorithms , the Center-of-Gravity (CoG), weighted CoG (WCoG) and Intensity Weighted Centroid (IWC), as well as those accuracies for various extended and elongated spots. In addition, we compared the reconstructed image data from those three algorithms with theoretical results, and proved that WCoG and IWC are the best wave front reconstruction algorithms for extended and elongated spot among all the algorithms.

Status of the GTC adaptive optics: integration in laboratory

NASA Astrophysics Data System (ADS)

Reyes García-Talavera, M.; Béjar, V. J. S.; López, J. C.; López, R. L.; Martín, C.; Martín, Y.; Montilla, I.; Núñez, M.; Puga, M.; Rodríguez, L. F.; Tenegi, F.; Tubío, O.; Bello, D.; Cavaller, L.; Prieto, G.; Rosado, M.

2016-07-01

Since the beginning of the development of the Gran Telescopio Canarias (GTC), an Adaptive Optics (AO) system was considered necessary to exploit the full diffraction-limited potential of the telescope. The GTC AO system designed during the last years is based on a single deformable mirror conjugated to the telescope pupil, and a Shack-Hartmann wavefront sensor with 20 x 20 subapertures, using an OCAM2 camera. The GTCAO system will provide a corrected beam with a Strehl Ratio (SR) of 0.65 in K-band with bright natural guide stars. Most of the subsystems have been manufactured and delivered. The upgrade for the operation with a Laser Guide Star (LGS) system has been recently approved. The present status of the GTCAO system, currently in its laboratory integration phase, is summarized in this paper.

Concept for polychromatic laser guide stars: one-photon excitation of the 4P3/2 level of a sodium atom.

PubMed

Pique, Jean-Paul; Moldovan, Ioana Cristina; Fesquet, Vincent

2006-11-01

One challenge for polychromatic laser guide stars is to create a sufficiently intense source in the UV. The flux required for the measurement of differential tip-tilt is the main issue that we address. We describe a model that has been validated using on-sky data. We present a method that excites the 4P3/2 sodium level using a one-photon excitation at 330 nm. It is more efficient than the two-photon excitation previously suggested since its power slope flux is 3 x 10(4) photons/s/m2/W instead of 1.3 x 10(3) photons/s/m2/W. This method is very promising both in terms of flux and system simplicity.

The Laser Guide Star System for Adaptive Optics at Subaru Telescope

NASA Astrophysics Data System (ADS)

Hayano, Y.; Saito, Y.; Ito, M.; Saito, N.; Akagawa, K.; Takazawa, A.; Ito, M.; Wada, S.; Takami, H.; Iye, M.

We report on the current status of developing the new laser guide star (LGS) system for the Subaru adaptive optics (AO) system. We have three major subsystems: the laser unit, the relay optical fiber and the laser launching telescope. A 4W-class all-solid-state 589nm laser has been developed as a light source for sodium laser guide star. We use two mode-locked Nd:YAG lasers operated at the wavelength of 1064nm and 1319nm to generate sum-frequency conversion into 589nm. The side-LD pumped configuration is used for the mode-locked Nd:YAG lasers. We have carefully considered the thermal lens effect in the cavity to achieve a high beam quality with TEM00; M2 = 1.06. The mode-locked frequency is selected at 143 MHz. We obtained the output powers of 16.5 W and 5.0 W at 1064nm and 1319 nm. Sum frequency generated by mixing two synchronized Nd:YAG mode-locked pulsed beams is precisely tuned to the sodium D2 line by thermal control of the etalon in the 1064nm Nd:YAG laser by observing the maximum fluorescence intensity of heated sodium vapor cell. The maximum output power at 589.159 nm reaches to 4.6 W using a PPMgOSLT crystal as a nonlinear optical crystal. And the output power can be maintained within a stability of +/- 1.2% for more than 3 days without optical damage. We developed a single-mode photonic crystal fiber (PCF) to relay the laser beam from laser clean room, in which the laser unit is located on the Nasmyth platform, to the laser launching telescope mounted behind the secondary mirror of Subaru Telescope. The photonic crystal fiber has solid pure silica core with the mode field diameter of 14 micron, which is relatively larger than that of the conventional step-index type single mode fiber. The length of the PCF is 35m and transmission loss due to the pure silica is 10dB/km at 589nm, which means PCF transmits 92% of the laser beam. We have preliminary achieved 75% throughput in total. Small mode-locked pulse width in time allows us to transmit the high-power laser beam with no suffer from the non-linear scatter effect, i.e. stimulated Brillouin scatter, in the PCF. The laser launching telescope (LLT) has an output clear aperture as 50 cm. It is classical Cassegrain type optical configuration with tertiary mirror to insert the laser beam from the side. The wavefront error is designed to be 60 to 70nm. The LLT is a copy product what European Southern Observatory has been designed for the laser guide star system at Very Large Telescope. We succeeded to launch the laser beam to the sky on October 12, 2006. After several tests on the sky, we succeeded to get an image of the laser guide star with the size of more than 10 arc second. The larger size of the laser guide star is caused by the large optical aberration on the primary mirror of LLT due to the heat stress generated at the trigonal support points. We are making a plan to repair this problem during June and the second laser launching test will start around this summer.

Astrometry of the omega Centauri Hubble Space Telescope Calibration Field

NASA Technical Reports Server (NTRS)

Mighell, Kenneth J.

2000-01-01

Astrometry, on the International Celestial Reference Frame (epoch J2000.0), is presented for the Walker (1994, PASP, 106, 828) stars in the omega Centauri (=NGC 5139=C 1323-1472) Hubble Space Telescope Wide Field/Planetary Camera (WF/PC) calibration field of Harris et al. (1993, AJ, 105, 1196). Harris et al. stars were first identified on a WFPC2 observation of the omega Cen HST calibration field. Relative astrometry of the Walker stars in this field was then obtained using Walker's CCD positions and astrometry derived using the STSDAS METRIC task on the positions of the Harris et al. stars on the WFPC2 observation. Finally, the relative astrometry, which was based on the HST Guide Star Catalog, is placed on the International Celestial Reference Frame with astrometry from the USNO-A2.0 catalog. An ASCII text version of the astrometric data of the Walker stars in the omega Cen HST calibration field is available electronically in the online version of the article.

Chico High School Students' Astrometric Observations of the Visual Double Star STF 1657

NASA Astrophysics Data System (ADS)

Ahiligwo, Jonelle; Bergamini, Clara; Berglund, Kallan; Bhardwaj, Mohit; Chelson, Spud; Costa, Amanda; Epis, Ashley; Grant, Azure; Osteen, Courtney; Reiner, Skyla; Rose, Adam; Schmidt, Emily; Sears, Forest; Sullivan-Hames, Maddie; Johnson, Jolyon

2012-01-01

In the spring of 2011, Chico Senior High School students participated in an astronomy seminar at the Gateway Science Museum, University of California, Chico. The observers used a Celestron NexStar 6 SE telescope and a Celestron MicroGuide eyepiece to determine the separation and position angle of the visual double star STF 1657. Observations were made in approximately one hour on the evening of May 1, 2011. The observers determined that the separation of STF 1657 was 22.1" and the position angle was 273.4&°. Seminar members then used the spectral type, parallax, and proper motion vectors of the two stars to determine if they are a line-of-sight optical pair or physically bound by gravity. Due to large errors in the parallax and the proper motion vector for the secondary star, the results were inconclusive. Through this experience, the students learned the skills needed to observe, analyze, and report on double stars.

Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernández-Trincado, J. G.; Geisler, D.; Tang, B.

We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] ≳ −1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similarmore » metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.« less

Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns

NASA Astrophysics Data System (ADS)

Fernández-Trincado, J. G.; Zamora, O.; García-Hernández, D. A.; Souto, Diogo; Dell'Agli, F.; Schiavon, R. P.; Geisler, D.; Tang, B.; Villanova, S.; Hasselquist, Sten; Mennickent, R. E.; Cunha, Katia; Shetrone, M.; Allende Prieto, Carlos; Vieira, K.; Zasowski, G.; Sobeck, J.; Hayes, C. R.; Majewski, S. R.; Placco, V. M.; Beers, T. C.; Schleicher, D. R. G.; Robin, A. C.; Mészáros, Sz.; Masseron, T.; García Pérez, Ana E.; Anders, F.; Meza, A.; Alves-Brito, A.; Carrera, R.; Minniti, D.; Lane, R. R.; Fernández-Alvar, E.; Moreno, E.; Pichardo, B.; Pérez-Villegas, A.; Schultheis, M.; Roman-Lopes, A.; Fuentes, C. E.; Nitschelm, C.; Harding, P.; Bizyaev, D.; Pan, K.; Oravetz, D.; Simmons, A.; Ivans, Inese I.; Blanco-Cuaresma, S.; Hernández, J.; Alonso-García, J.; Valenzuela, O.; Chanamé, J.

2017-09-01

We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] ≳ -1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.

Assessment of visiting activities for young children using the UNAWE Evaluation Guide

NASA Astrophysics Data System (ADS)

Tomita, Akihiko

2015-08-01

When the target is young children and the activity type is play, the assessment of the activity is not easy. The table of domains of active learning shown in the EU Universe Awareness Programme Evaluation Guide is useful for the assessment; the Guide shows the four domains; motivation, scientific skills, universe knowledge, and intercultural attitudes, and many items of objectives in each domains. The Guide can be a basic format and the items can be modified so as to fit each activity. Taking my activity as an example, I will present an assessment using the Guide. The activity I will present is "Uchu no O-hanashi," a visiting activity which includeds slide show, story telling, and enjoying pictures on large sheets for children at nursery, kindergarten, preschool and other sites. In order to obtain the data, I have recorded the voice of children. The analysis method is a kind of qualitative one. I picked up "motivation" and "scientific skills" words from the record when they muttered about and asked each other what they felt, what they found, and what they got excited about. Among the items in the "scientific skills domain," looking at carefully, asking, exchanging opinions, interpreting or trying to interpret, and trying were frequently appeared. Other skills such as devising and confirming were not frequently appeared but they would sometimes appear later at home or at school after the activity. I also picked up the words of children obtaining scientific way of view and attitude through the activity. One example is "It seems that stars float in the sky and do not move. Do they really set like the Sun, our nearest star? I never saw stars set!" A boy was trying to make a new framework for his understanding. This kind of thinking will enrich his or her future "universe knowledge" and "intercultural attitudes."

DDN (Defence Data Network) Protocol Implementations and Vendors Guide

DTIC Science & Technology

1988-08-01

Artificial Intelligence Laboratory Room NE43-723 545 Technology Square Cambridge, MA 02139 (617) 253-8843 S John Wroclawski, (JTW@AI.AJ.MIT.EDU...Massachusetts Institute of Technology Artificial Intelligence Laboratory Room NE43-743 545 Technology Square 0 Cambridge, MA 02139 (617) 253-7885 ORDERING...TCP/IP Network Software for PC-DOS Systems CPU: IBM-PC/XT/AT/compatible in conjunction with EXOS 205 Inteligent Ethernet Controller for PCbus 0/s

Optical System Error Analysis and Calibration Method of High-Accuracy Star Trackers

PubMed Central

Sun, Ting; Xing, Fei; You, Zheng

2013-01-01

The star tracker is a high-accuracy attitude measurement device widely used in spacecraft. Its performance depends largely on the precision of the optical system parameters. Therefore, the analysis of the optical system parameter errors and a precise calibration model are crucial to the accuracy of the star tracker. Research in this field is relatively lacking a systematic and universal analysis up to now. This paper proposes in detail an approach for the synthetic error analysis of the star tracker, without the complicated theoretical derivation. This approach can determine the error propagation relationship of the star tracker, and can build intuitively and systematically an error model. The analysis results can be used as a foundation and a guide for the optical design, calibration, and compensation of the star tracker. A calibration experiment is designed and conducted. Excellent calibration results are achieved based on the calibration model. To summarize, the error analysis approach and the calibration method are proved to be adequate and precise, and could provide an important guarantee for the design, manufacture, and measurement of high-accuracy star trackers. PMID:23567527

The Large Binocular Telescope's ARGOS ground-layer AO system

NASA Astrophysics Data System (ADS)

Hart, M.; Rabien, S.; Busoni, L.; Barl, L.; Bechmann, U.; Bonaglia, M.; Boose, Y.; Borelli, J.; Bluemchen, T.; Carbonaro, L.; Connot, C.; Deysenroth, M.; Davies, R.; Durney, O.; Elberich, M.; Ertl, T.; Esposito, S.; Gaessler, W.; Gasho, V.; Gemperlein, H.; Hubbard, P.; Kanneganti, S.; Kulas, M.; Newman, K.; Noenickx, J.; Orban de Xivry, G.; Qirrenback, A.; Rademacher, M.; Schwab, C.; Storm, J.; Vaitheeswaran, V.; Weigelt, G.; Ziegleder, J.

2011-09-01

ARGOS, the laser-guided adaptive optics system for the Large Binocular Telescope (LBT), is now under construction at the telescope. By correcting atmospheric turbulence close to the telescope, the system is designed to deliver high resolution near infrared images over a field of 4 arc minute diameter. ARGOS is motivated by a successful prototype multi-laser guide star system on the 6.5 m MMT telescope, results from which are presented in this paper. At the LBT, each side of the twin 8.4 m aperture is being equipped with three Rayleigh laser guide stars derived from six 18 W pulsed green lasers and projected into two triangular constellations matching the size of the corrected field. The returning light is to be detected by wavefront sensors that are range gated within the seeinglimited depth of focus of the telescope. Wavefront correction will be introduced by the telescope’s deformable secondary mirrors driven on the basis of the average wavefront errors computed from the respective guide star constellation. Measured atmospheric turbulence profiles from the site lead us to expect that by compensating the ground-layer turbulence, ARGOS will deliver median image quality of about 0.2 arc sec in the near infrared bands. This will be exploited by a pair of multi-object near-IR spectrographs, LUCI1 and LUCI2, each with 4 arc minute field already operating on the telescope. In future, ARGOS will also feed two interferometric imaging instruments, the LBT Interferometer operating in the thermal infrared, and LINC-NIRVANA, operating at visible and near infrared wavelengths. Together, these instruments will offer very broad spectral coverage at the diffraction limit of the LBT’s combined aperture, 23 m in size.

KSC-2009-1652

NASA Image and Video Library

2009-02-16

CAPE CANAVERAL, Fla. – At the Hazardous Processing Facility at Astrotech in Titusville, Fla., workers guide the suspended Kepler spacecraft onto a Delta II third stage. Kepler is designed to survey more than 100,000 stars in our galaxy to determine the number of sun-like stars that have Earth-size and larger planets, including those that lie in a star's "habitable zone," a region where liquid water, and perhaps life, could exist. If these Earth-size worlds do exist around stars like our sun, Kepler is expected to be the first to find them and the first to measure how common they are. The liftoff of Kepler aboard a Delta II rocket is currently targeted for 10:48 p.m. EST March 5 from Space Launch Complex 17 on Cape Canaveral Air Force Station. Photo credit: NASA/Troy Cryder

L: How Long Do They Last?

NASA Astrophysics Data System (ADS)

Shostak, Seth

The Drake equation, a commonly-used starting point for discussions about the likelihood of finding extraterrestrial intelligence, is now nearly a halfcentury old. It dates from 1961, a year after Frank Drake made his pioneering radio search for artificial signals from other worlds. That search, dubbed Project Ozma, was a 200-hour scrutiny of two nearby, Sun-like stars for transmissions spectrally situated near the 1420 MHz line of neutral hydrogen, and was conducted with an 85-foot antenna at the National Radio Astronomy Observatory in Green Bank, West Virginia (Drake, 1960; Kellermann and Seielstad, 1986). These efforts to find easy evidence of intelligence in other star systems provoked considerable public interest, including a major article in Saturday Review (Lear, 1960).

Simultaneous Planning and Control for Autonomous Ground Vehicles

DTIC Science & Technology

2009-02-01

these applications is called A * ( A -star), and it was originally developed by Hart, Nilsson, and Raphael [HAR68]. Their research presented the formal...sequence, rather than a dynamic programming approach. A * search is a technique originally developed for Artificial Intelligence 43 applications ... developed at the Center for Intelligent Machines and Robotics, serves as a platform for the implementation and testing discussed. autonomous

True-sky demonstration of an autonomous star tracker

NASA Astrophysics Data System (ADS)

van Bezooijen, Roelof W.

1994-07-01

An autonomous star tracker (AST) is basically a `star field in, attitude out' device capable of determining its attitude without requiring any a priori attitude knowledge. In addition to this attitude acquisition capability, an AST can perform attitude updates autonomously and is able to provide its attitude `continuously' while tracking a star field. The Lockheed Palo Alto Research Laboratory is developing a reliable, low-cost, miniature AST that has a one arcsec overall accuracy, weighs less than 1.5 kg, consumes less than 7 watts of power, and is sufficiently sensitive to be used at all sky locations. The device performs attitude acquisition in a fraction of a second and outputs its attitude at a 10 Hz rate when operating in its tracking mode. Besides providing the functionality needed for future advanced attitude control and navigation systems, an AST also improves spacecraft reliability, mass, power, cost, and operating expenses. The AST comprises a-thermalized, refractive optics, a frame-transfer CCD with a sensitive area of 1024 by 1024 pixels, camera electronics implemented with application- specific integrated circuits, a compact single board computer with a radiation hard 32 bit RISC processor, and an all-sky guide star database. Star identification is performed by a memory- efficient and highly robust algorithm that finds the largest group of observed stars matching a group of guide stars. An important milestone has recently been achieved with the validation of the attitude acquisition capability through correct and rapid identification of all 704 true-sky star fields obtained at the Lick Observatory, using an uncalibrated prototype AST with a 512 by 1024 pixel frame-transfer CCD and a 50 mm f/1.2 lens that provided an effective 6.5 by 13.2 degree field of view. The overlapping fields cover 47% of the sky, including both rich and sparse areas. The paper contains a description of the AST, a summary of the functions enabled or improved by the device, an overview of the identification algorithm, results obtained with a realistic simulation program, a description of the true-sky star field identification method and a presentation of the results obtained. The AST tolerates the presence of bright objects as was demonstrated by a field that included Jupiter.

Artificial intelligence: the clinician of the future.

PubMed

Gallagher, S M

2001-09-01

Human beings have long been fascinated with the idea of artificial intelligence. This fascination is fueled by popular films such as Stanley Kubrick's 2001: A Space Odyssey and Stephen Spielberg's recent film, AI. However intriguing artificial intelligence may be, Hubert and Spencer Dreyfus contend that qualities exist that are uniquely human--the qualities thought to be inaccessible to the computer "mind." Patricia Benner further investigated the qualities that guide clinicians in making decisions and assessments that are not entirely evidence-based or grounded in scientific data. Perhaps it is the intuitive nature of the human being that separates us from the machine. The state of artificial intelligence is described herein, along with a discussion of computerized clinical decision-making and the role of the human being in these decisions.

Degree of Biomimicry of Artificial Spider Silk Spinning Assessed by NMR Spectroscopy.

PubMed

Otikovs, Martins; Andersson, Marlene; Jia, Qiupin; Nordling, Kerstin; Meng, Qing; Andreas, Loren B; Pintacuda, Guido; Johansson, Jan; Rising, Anna; Jaudzems, Kristaps

2017-10-02

Biomimetic spinning of artificial spider silk requires that the terminal domains of designed minispidroins undergo specific structural changes in concert with the β-sheet conversion of the repetitive region. Herein, we combine solution and solid-state NMR methods to probe domain-specific structural changes in the NT2RepCT minispidroin, which allows us to assess the degree of biomimicry of artificial silk spinning. In addition, we show that the structural effects of post-spinning procedures can be examined. By studying the impact of NT2RepCT fiber drying, we observed a reversible beta-to-alpha conversion. We think that this approach will be useful for guiding the optimization of artificial spider silk fibers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Native Skywatchers and the Makoc&dotbelow;e Wic&dotbelow;aŋḣpi Wowapi—D(L)akota Star Map—Building Community Around Native Star Knowledge

NASA Astrophysics Data System (ADS)

Lee, A. S.; Rock, J.

2014-07-01

In D(L)akota the Big Dipper is known as To/ToŋWiŋ—Blue/Birth Woman. She lives at the center of the scoop in the Big Dipper and is the door keeper between the star world and the Earth. The same group of seven bright stars is also known as Wịakiyuhapi, the Stretcher, and Waṡihdapi/Waṡiglapi, the Mourners. This is the beginning of the journey back into the spirit world for those leaving the Earth. Embedded in the native constellations are teachings that help guide and inspire native peoples. This workshop will present the D(L)akota Star Map and constellations of the current night sky. The Native Skywatchers research and programming seeks out elders, culture teachers, and community members to discuss the Ojibwe and D(L)akota star knowledge. Together we have created Makoc&dotbelow;e Wic&dotbelow;aŋḣpi Wowapi—D(L)akota Star Map. This map and related curriculum was published and disseminated to regional educators at our Native Skywatchers Middle School Teacher workshops in June 2012 and 2013. We are building community around the native star knowledge.

Artificial Intelligence and the Brave New World of Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Devinney, E.; Guinan, E.; Bradstreet, D.; DeGeorge, M.; Giammarco, J.; Alcock, C.; Engle, S.

2005-12-01

The explosive growth of observational capabilities and information technology over the past decade has brought astronomy to a tipping point - we are going to be deluged by a virtual fire hose (more like Niagara Falls!) of data. An important component of this deluge will be newly discovered eclipsing binary stars (EBs) and other valuable variable stars. As exploration of the Local Group Galaxies grows via current and new ground-based and satellite programs, the number of EBs is expected to grow explosively from some 10,000 today to 8 million as GAIA comes online. These observational advances will present a unique opportunity to study the properties of EBs formed in galaxies with vastly different dynamical, star formation, and chemical histories than our home Galaxy. Thus the study of these binaries (e.g., from light curve analyses) is expected to provide clues about the star formation rates and dynamics of their host galaxies as well as the possible effects of varying chemical abundance on stellar evolution and structure. Additionally, minimal-assumption-based distances to Local Group objects (and possibly 3-D mapping within these objects) shall be returned. These huge datasets of binary stars will provide tests of current theories (or suggest new theories) regarding binary star formation and evolution. However, these enormous data will far exceed the capabilities of analysis via human examination. To meet the daunting challenge of successfully mining this vast potential of EBs and variable stars for astrophysical results with minimum human intervention, we are developing new data processing techniques and methodologies. Faced with an overwhelming volume of data, our goal is to integrate technologies of Machine Learning and Pattern Processing (Artificial Intelligence [AI]) into the data processing pipelines of the major current and future ground- and space-based observational programs. Data pipelines of the future will have to carry us from observations to astrophysics with minimal human intervention. While there has been some recognition of this need (e.g. the LSST project drawing on the experience of MACHO/OGLE), few steps have been taken to address this crucial issue. Fortunately, advances in AI have created the opportunity to make significant progress in this direction. Here we discuss our plans to develop an Intelligent Data Pipeline (IDP) that can operate autonomously on large observational datasets to produce results of astrophysical value. Plans and initial results are discussed. This research is supported by NSF/RUI Grant AST05-07542 which we gratefully acknowledge.

Your Dialysis Care Team

MedlinePlus

... A to Z Health Guide Your Dialysis Care Team Tweet Share Print Email Good health care is ... dialyzers (artificial kidneys) for reuse. Vascular Access Care Team If you are a hemodialysis patient, another group ...

Line of Sight Stabilization of James Webb Space Telescope

NASA Technical Reports Server (NTRS)

Meza, Luis; Tung, Frank; Anandakrishnan, Satya; Spector, Victor; Hyde, Tupper

2005-01-01

The James Webb Space Telescope (JWST) builds upon the successful flight experience of the Chandra Xray Telescope by incorporating an additional LOS pointing servo to meet the more stringent pointing requirements. The LOS pointing servo, referred to in JWST as the Fine Guidance Control System (FGCS), will utilize a Fine Guidance Sensor (FGS) as the sensor, and a Fine Steering Mirror (FSM) as the actuator. The FSM is a part of the Optical Telescope Element (OTE) and is in the optical path between the tertiary mirror and the instrument focal plane, while the FGS is part of the Integrated Science Instrument Module (ISIM). The basic Chandra spacecraft bus attitude control and determination architecture, utilizing gyros, star trackers/aspect camera, and reaction wheels, is retained for JWST. This system has achieved pointing stability of better than 0.5 arcseconds. To reach the JWST requirements of milli-arcsecond pointing stability with this ACS hardware, the local FGCS loop is added to the optical path. The FGCS bandwidth is about 2.0 Hz and will therefore attenuate much of the spacecraft ACS induced low frequency jitter. In order to attenuate the higher frequency (greatet than 2.0 Hz) disturbances associated with reaction wheel static and dynamic imbalances, as well as bearing run-out, JWST will employ a two-stage passive vibration isolation system consisting of (1) 7.0 Hz reaction wheel isolators between each reaction wheel and the spacecraft bus, and (2) a 1.0 Hz tower isolator between the spacecraft bus and the Optical Telescope Element (OTE). In order to sense and measure the LOS, the FGS behaves much like an autonomous star tracker that has a very small field of view and uses the optics of the telescope. It performs the functions of acquisition, identification and tracking of stars in its 2.5 x 2.5 arcminute field of view (FOV), and provides the centroid and magnitude of the selected star for use in LOS control. However, since only a single star is being tracked at any time within the FGS FOV there is only tip and tilt information; rotation about the FGS LOS will not be sensed. The FGCS uses the FSM to move the guide star within the FGS FOV and place the centroid of the guide star at any desired position within the FGS focal plane. Using this architecture allows the FGCS to correct the low frequency LOS jitter that is induced by the spacecraft ACS in pitch and yaw, and achieve the milli-arcsecond pointing stability required by JWST. The less stringent ISIM FOV roll performance will be provided solely by the ACS, using the spacecraft gyros and star trackers. Since the FSM is in the optical path, the pointing stabilrty of a science object in any of the instruments will be similar to that of the guide star LOS.

A search for ejecta nebulae around Wolf-Rayet stars using the SHS Hα survey

NASA Astrophysics Data System (ADS)

Stock, D. J.; Barlow, M. J.

2010-12-01

Recent large-scale Galactic plane Hα surveys allow a re-examination of the environs of Wolf-Rayet (WR) stars for the presence of a circumstellar nebula. Using the morphologies of WR nebulae known to be composed of stellar ejecta as a guide, we constructed ejecta nebula criteria similar to those of Chu and searched for likely WR ejecta nebulae in the Southern Hα Survey (SHS). A new WR ejecta nebula around WR 8 is found and its morphology is discussed. The fraction of WR stars with ejecta-type nebulae is roughly consistent between the Milky Way (MW) and Large Magellanic Cloud (LMC) at around 5-6 per cent, with the MW sample dominated by nitrogen-rich WR central stars (WN type) and the LMC stars having a higher proportion of carbon-rich WR central stars (WC type). We compare our results with those of previous surveys, including those of Marston and Miller & Chu, and find broad consistency. We investigate several trends in the sample: most of the clear examples of ejecta nebulae have WNh central stars, and very few ejecta nebulae have binary central stars. Finally, the possibly unique evolutionary status of the nebula around the binary star WR 71 is explored.

Comparison Study II: Double Star Measurements Made Using an Equatorial Mounted Refractor and an Alt-Az Mounted Reflector

NASA Astrophysics Data System (ADS)

Frey, Thomas G.; Coombs, Lee C.

2012-07-01

Eight double stars with separations between 13 and 48 arc seconds were studied. Their separations and position angles were measured using an equatorial mounted refractor and and alt-az mounted reflector. A 2x Barlow lens was used along with a Celestron Micro Guide eyepiece to magnify the separation. Comparison of the possible effect of magnitude difference on the separation and position angle measurements was investigated.

User's guide for vectorized code EQUIL for calculating equilibrium chemistry on Control Data STAR-100 computer

NASA Technical Reports Server (NTRS)

Kumar, A.; Graves, R. A., Jr.; Weilmuenster, K. J.

1980-01-01

A vectorized code, EQUIL, was developed for calculating the equilibrium chemistry of a reacting gas mixture on the Control Data STAR-100 computer. The code provides species mole fractions, mass fractions, and thermodynamic and transport properties of the mixture for given temperature, pressure, and elemental mass fractions. The code is set up for the electrons H, He, C, O, N system of elements. In all, 24 chemical species are included.

Near-infrared image-guided laser ablation of artificial caries lesions.

PubMed

Tao, You-Chen; Fan, Kenneth; Fried, Daniel

2007-01-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. The objective of this study was to test the hypothesis that two-dimensional NIR images of demineralized tooth surfaces can be used to guide CO(2) laser ablation for the selective removal of artificial caries lesions. Highly patterned artificial lesions were produced by submerging 5 × 5 mm(2) bovine enamel samples in demineralized solution for a 9-day period while sound areas were protected with acid resistant varnish. NIR imaging and polarization sensitive optical coherence tomography (PS-OCT) were used to acquire depth-resolved images at a wavelength of 1310-nm. An imaging processing module was developed to analyze the NIR images and to generate optical maps. The optical maps were used to control a CO(2) laser for the selective removal of the lesions at a uniform depth. This experiment showed that the patterned artificial lesions were removed selectively using the optical maps with minimal damage to sound enamel areas. Post-ablation NIR and PS-OCT imaging confirmed that demineralized areas were removed while sound enamel was conserved. This study successfully demonstrated that near-IR imaging can be integrated with a CO(2) laser ablation system for the selective removal of dental caries.

Near-infrared image-guided laser ablation of artificial caries lesions

PubMed Central

Tao, You-Chen; Fan, Kenneth; Fried, Daniel

2012-01-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. The objective of this study was to test the hypothesis that two–dimensional NIR images of demineralized tooth surfaces can be used to guide CO2 laser ablation for the selective removal of artificial caries lesions. Highly patterned artificial lesions were produced by submerging 5 × 5 mm2 bovine enamel samples in demineralized solution for a 9-day period while sound areas were protected with acid resistant varnish. NIR imaging and polarization sensitive optical coherence tomography (PS-OCT) were used to acquire depth-resolved images at a wavelength of 1310-nm. An imaging processing module was developed to analyze the NIR images and to generate optical maps. The optical maps were used to control a CO2 laser for the selective removal of the lesions at a uniform depth. This experiment showed that the patterned artificial lesions were removed selectively using the optical maps with minimal damage to sound enamel areas. Post-ablation NIR and PS-OCT imaging confirmed that demineralized areas were removed while sound enamel was conserved. This study successfully demonstrated that near-IR imaging can be integrated with a CO2 laser ablation system for the selective removal of dental caries. PMID:22866210

Near-infrared image-guided laser ablation of artificial caries lesions

NASA Astrophysics Data System (ADS)

Tao, You-Chen; Fan, Kenneth; Fried, Daniel

2007-02-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. The objective of this study was to test the hypothesis that two-dimensional NIR images of demineralized tooth surfaces can be used to guide CO II laser ablation for the selective removal of artificial caries lesions. Highly patterned artificial lesions were produced by submerging 5 x 5 mm2 bovine enamel samples in demineralized solution for a 9-day period while sound areas were protected with acid resistant varnish. NIR imaging and polarization sensitive optical coherence tomography (PS-OCT) were used to acquire depth-resolved images at a wavelength of 1310-nm. An imaging processing module was developed to analyze the NIR images and to generate optical maps. The optical maps were used to control a CO II laser for the selective removal of the lesions at a uniform depth. This experiment showed that the patterned artificial lesions were removed selectively using the optical maps with minimal damage to sound enamel areas. Post-ablation NIR and PS-OCT imaging confirmed that demineralized areas were removed while sound enamel was conserved. This study successfully demonstrated that near-IR imaging can be integrated with a CO II laser ablation system for the selective removal of dental caries.

Conceptual design for a user-friendly adaptive optics system at Lick Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bissinger, H.D.; Olivier, S.; Max, C.

1996-03-08

In this paper, we present a conceptual design for a general-purpose adaptive optics system, usable with all Cassegrain facility instruments on the 3 meter Shane telescope at the University of California`s Lick Observatory located on Mt. Hamilton near San Jose, California. The overall design goal for this system is to take the sodium-layer laser guide star adaptive optics technology out of the demonstration stage and to build a user-friendly astronomical tool. The emphasis will be on ease of calibration, improved stability and operational simplicity in order to allow the system to be run routinely by observatory staff. A prototype adaptivemore » optics system and a 20 watt sodium-layer laser guide star system have already been built at Lawrence Livermore National Laboratory for use at Lick Observatory. The design presented in this paper is for a next- generation adaptive optics system that extends the capabilities of the prototype system into the visible with more degrees of freedom. When coupled with a laser guide star system that is upgraded to a power matching the new adaptive optics system, the combined system will produce diffraction-limited images for near-IR cameras. Atmospheric correction at wavelengths of 0.6-1 mm will significantly increase the throughput of the most heavily used facility instrument at Lick, the Kast Spectrograph, and will allow it to operate with smaller slit widths and deeper limiting magnitudes. 8 refs., 2 figs.« less

Mesospheric sodium structure variability on horizontal scales relevant to laser guide star asterisms

NASA Astrophysics Data System (ADS)

Pfrommer, Thomas; Hickson, Paul

2012-07-01

Adaptive optics (AO) systems of modern telescopes use laser guide stars, produced by resonant excitation of sodium atoms in the mesosphere at around 92 km. Wavefront sensor subapertures, if sufficiently far away from the primary mirror center, resolve the internal structure of the sodium layer. The variability of this structure is caused by the influence of gravity waves and wind shear turbulence. The relevance of such dynamics to AO has been investigated over the past four years. A high-resolution lidar system, employed at the 6-m liquid mirror telescope, which is located near Vancouver, Canada, has been used to study mesospheric dynamics, such as the temporal behavior of the mean altitude. The main results from this study have been published elsewhere and will be summarized here. Along with the temporal variability, the mean altitude on horizontal scales of order IOs of meters has been studied by introducing a tip/tilt stage in the experimental setup. This enables us to swap the laser pulse within a 1 arcmin field of view. The horizontal mean altitude structure function has been measured on 10 observing nights between July and August 2011. Results reveal severe structural differences and a strong horizontal anisotropy. Individual laser beacons in a laser guide star asterism will therefore have at the same time significantly different focus heights. By propagating this 2d structure function to the entrance pupil of a 39 m telescope, we derive a differential focus wavefront error map.

Feasibility of Respiratory Triggering for MR-Guided Microwave Ablation of Liver Tumors Under General Anesthesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morikawa, Shigehiro, E-mail: morikawa@belle.shiga-med.ac.jp; Inubushi, Toshiro; Kurumi, Yoshimasa

2004-08-15

We obtained clear and reproducible MR fluoroscopic images and temperature maps for MR image-guided microwave ablation of liver tumors under general anesthesia without suspending the artificial ventilation. Respiratory information was directly obtained from air-way pressure without a sensor on the chest wall. The trigger signal started scanning of one whole image with a spoiled gradient echo sequence. The delay time before the start of scanning was adjusted to acquire the data corresponding to the k-space center at the maximal expiratory phase. The triggered images were apparently clearer than the nontriggered ones and the location of the liver was consistent, whichmore » made targeting of the tumor easy. MR temperature images, which were highly susceptible to the movement of the liver, during microwave ablation using a proton resonance frequency method, could be obtained without suspending the artificial ventilation. Respiratory triggering technique was found to be useful for MR fluoroscopic images and MR temperature monitoring in MR-guided microwave ablation of liver tumors under general anesthesia.« less

Programmable DNA-Guided Artificial Restriction Enzymes.

PubMed

Enghiad, Behnam; Zhao, Huimin

2017-05-19

Restriction enzymes are essential tools for recombinant DNA technology that have revolutionized modern biological research. However, they have limited sequence specificity and availability. Here we report a Pyrococcus furiosus Argonaute (PfAgo) based platform for generating artificial restriction enzymes (AREs) capable of recognizing and cleaving DNA sequences at virtually any arbitrary site and generating defined sticky ends of varying length. Short DNA guides are used to direct PfAgo to target sites for cleavage at high temperatures (>87 °C) followed by reannealing of the cleaved single stranded DNAs. We used this platform to generate over 18 AREs for DNA fingerprinting and molecular cloning of PCR-amplified or genomic DNAs. These AREs work as efficiently as their naturally occurring counterparts, and some of them even do not have any naturally occurring counterparts, demonstrating easy programmability, generality, versatility, and high efficiency for this new technology.

On the estimation of stellar parameters with uncertainty prediction from Generative Artificial Neural Networks: application to Gaia RVS simulated spectra

NASA Astrophysics Data System (ADS)

Dafonte, C.; Fustes, D.; Manteiga, M.; Garabato, D.; Álvarez, M. A.; Ulla, A.; Allende Prieto, C.

2016-10-01

Aims: We present an innovative artificial neural network (ANN) architecture, called Generative ANN (GANN), that computes the forward model, that is it learns the function that relates the unknown outputs (stellar atmospheric parameters, in this case) to the given inputs (spectra). Such a model can be integrated in a Bayesian framework to estimate the posterior distribution of the outputs. Methods: The architecture of the GANN follows the same scheme as a normal ANN, but with the inputs and outputs inverted. We train the network with the set of atmospheric parameters (Teff, log g, [Fe/H] and [α/ Fe]), obtaining the stellar spectra for such inputs. The residuals between the spectra in the grid and the estimated spectra are minimized using a validation dataset to keep solutions as general as possible. Results: The performance of both conventional ANNs and GANNs to estimate the stellar parameters as a function of the star brightness is presented and compared for different Galactic populations. GANNs provide significantly improved parameterizations for early and intermediate spectral types with rich and intermediate metallicities. The behaviour of both algorithms is very similar for our sample of late-type stars, obtaining residuals in the derivation of [Fe/H] and [α/ Fe] below 0.1 dex for stars with Gaia magnitude Grvs < 12, which accounts for a number in the order of four million stars to be observed by the Radial Velocity Spectrograph of the Gaia satellite. Conclusions: Uncertainty estimation of computed astrophysical parameters is crucial for the validation of the parameterization itself and for the subsequent exploitation by the astronomical community. GANNs produce not only the parameters for a given spectrum, but a goodness-of-fit between the observed spectrum and the predicted one for a given set of parameters. Moreover, they allow us to obtain the full posterior distribution over the astrophysical parameters space once a noise model is assumed. This can be used for novelty detection and quality assessment.

A fast and efficient python library for interfacing with the Biological Magnetic Resonance Data Bank.

PubMed

Smelter, Andrey; Astra, Morgan; Moseley, Hunter N B

2017-03-17

The Biological Magnetic Resonance Data Bank (BMRB) is a public repository of Nuclear Magnetic Resonance (NMR) spectroscopic data of biological macromolecules. It is an important resource for many researchers using NMR to study structural, biophysical, and biochemical properties of biological macromolecules. It is primarily maintained and accessed in a flat file ASCII format known as NMR-STAR. While the format is human readable, the size of most BMRB entries makes computer readability and explicit representation a practical requirement for almost any rigorous systematic analysis. To aid in the use of this public resource, we have developed a package called nmrstarlib in the popular open-source programming language Python. The nmrstarlib's implementation is very efficient, both in design and execution. The library has facilities for reading and writing both NMR-STAR version 2.1 and 3.1 formatted files, parsing them into usable Python dictionary- and list-based data structures, making access and manipulation of the experimental data very natural within Python programs (i.e. "saveframe" and "loop" records represented as individual Python dictionary data structures). Another major advantage of this design is that data stored in original NMR-STAR can be easily converted into its equivalent JavaScript Object Notation (JSON) format, a lightweight data interchange format, facilitating data access and manipulation using Python and any other programming language that implements a JSON parser/generator (i.e., all popular programming languages). We have also developed tools to visualize assigned chemical shift values and to convert between NMR-STAR and JSONized NMR-STAR formatted files. Full API Reference Documentation, User Guide and Tutorial with code examples are also available. We have tested this new library on all current BMRB entries: 100% of all entries are parsed without any errors for both NMR-STAR version 2.1 and version 3.1 formatted files. We also compared our software to three currently available Python libraries for parsing NMR-STAR formatted files: PyStarLib, NMRPyStar, and PyNMRSTAR. The nmrstarlib package is a simple, fast, and efficient library for accessing data from the BMRB. The library provides an intuitive dictionary-based interface with which Python programs can read, edit, and write NMR-STAR formatted files and their equivalent JSONized NMR-STAR files. The nmrstarlib package can be used as a library for accessing and manipulating data stored in NMR-STAR files and as a command-line tool to convert from NMR-STAR file format into its equivalent JSON file format and vice versa, and to visualize chemical shift values. Furthermore, the nmrstarlib implementation provides a guide for effectively JSONizing other older scientific formats, improving the FAIRness of data in these formats.

AGN contamination in total infrared determined star formation rates in dusty galaxies at z~2-3

NASA Astrophysics Data System (ADS)

Mazzei, Renato; Sharon, Chelsea E.; Riechers, Dominik

2017-01-01

Along with theoretical work that suggests feedback from active galactic nuclei (AGN) may quench star formation in massive galaxies, the temporal coincidence between the peak of cosmic star formation rates and black hole accretion rates suggests that AGN are common in star forming galaxies at z~2-3. Since star forming galaxies at these epochs are also very dusty, it is important that we correct galaxies’ long-wavelength properties for the presence of dust-obscured AGN in order to accurately capture their star formation rates and gas characteristics. We present a spectral energy distribution (SED) analysis of several un-lensed z~2-3 dusty star-forming galaxies from Pope et al. (2008) and Coppin et al. (2010), which we compare to several other high-z starbursts with well sampled SEDs. We constructed dust SEDs from existing Spitzer, Herschel, and SCUBA-2 photometry catalogues with data between 3.6 and 850 μm. For the SED fits, we used the Code Investigating GALaxy Emission (CIGALE), since it self-consistently determines the dust attenuation of stars and dust emission in the infrared in addition to determining the dust emission from obscured AGN (Noll et al. 2009; Serra et al. 2011). Our best-fit SEDs have typical reduced χ2 values between 0.2 and ~3. We use the output from CIGALE to determine the fraction of the total infrared luminosity (LTIR 8-1000 um) from star formation and from any potential obscured AGN. In order to examine the effects of buried AGN on the integrated Schmidt-Kennicutt relation (log(LTIR) vs. log(L'CO)), we compare our new LTIR to recently obtained CO(1-0) line luminosities from the Karl G. Jansky Very Large Array. Unaccounted for dust emission from AGN can artificially inflate the star formation rate inferred from LTIR, and may therefore offset starburst galaxies from the local Schmidt-Kennicutt relation and increase the slope of the relation, which can affect the inferred drivers of star formation.

Teacher's Guide for Computational Models of Animal Behavior: A Computer-Based Curriculum Unit to Accompany the Elementary Science Study Guide "Behavior of Mealworms." Artificial Intelligence Memo No. 432.

ERIC Educational Resources Information Center

Abelson, Hal; Goldenberg, Paul

This experimental curriculum unit suggests how dramatic innovations in classroom content may be achieved through use of computers. The computational perspective is viewed as one which can enrich and transform traditional curricula, act as a focus for integrating insights from diverse disciplines, and enable learning to become more active and…

Atmospherical wavefront phases using the plenoptic sensor (real data)

NASA Astrophysics Data System (ADS)

Rodríguez-Ramos, L. F.; Montilla, I.; Lüke, J. P.; López, R.; Marichal-Hernández, J. G.; Trujillo-Sevilla, J.; Femenía, B.; López, M.; Fernández-Valdivia, J. J.; Puga, M.; Rosa, F.; Rodríguez-Ramos, J. M.

2012-06-01

Plenoptic cameras have been developed the last years as a passive method for 3d scanning, allowing focal stack capture from a single shot. But data recorded by this kind of sensors can also be used to extract the wavefront phases associated to the atmospheric turbulence in an astronomical observation. The terrestrial atmosphere degrades the telescope images due to the diffraction index changes associated to the turbulence. Na artificial Laser Guide Stars (Na-LGS, 90km high) must be used to obtain the reference wavefront phase and the Optical Transfer Function of the system, but they are affected by defocus because of the finite distance to the telescope. Using the telescope as a plenoptic camera allows us to correct the defocus and to recover the wavefront phase tomographically, taking advantage of the two principal characteristics of the plenoptic sensors at the same time: 3D scanning and wavefront sensing. Then, the plenoptic sensors can be studied and used as an alternative wavefront sensor for Adaptive Optics, particularly relevant when Extremely Large Telescopes projects are being undertaken. In this paper, we will present the first observational wavefront phases extracted from real astronomical observations, using punctual and extended objects, and we show that the restored wavefronts match the Kolmogorov atmospheric turbulence.

The Stellar Cusp in the Galactic Center: Three-Dimensional Orbits of Stars

NASA Astrophysics Data System (ADS)

Chappell, Samantha; Ghez, Andrea M.; Boehle, Anna; Yelda, Sylvana; Sitarski, Breann; Witzel, Gunther; Do, Tuan; Lu, Jessica R.; Morris, Mark; Becklin, Eric E.

2015-01-01

We present new findings from our long term study of the nuclear star cluster around the Galaxy's central supermassive blackhole (SMBH). Measurements where made using speckle and laser guided adaptive optics imaging and integral field spectroscopy on the Keck telescopes. We report 13 new measurable accelerating sources around the SMBH, down to ~17 mag in K band, only 4 of which are known to be young stars, the rest are either known to be old stars or have yet to be spectral typed. Thus we more than double the number of measured accelerations for the known old stars and unknown spectral type population (increasing the number from 6 to 15). Previous observations suggest a flat density profile of late-type stars, contrary to the theorized Bahcall-Wolf cusp (Bahcall & Wolf 1976, 1977; Buchholz et al. 2009; Do et al. 2009; Bartko et al. 2010). With three-dimensional orbits of significantly accelerating sources, we will be able to better characterize the stellar cusp in the Galactic center, including the slope of the stellar density profile.

High Resolution Active Optics Observations from the Kepler Follow-up Observation Program

NASA Astrophysics Data System (ADS)

Gautier, Thomas N.; Ciardi, D. R.; Marcy, G. W.; Hirsch, L.

2014-01-01

The ground based follow-up observation program for candidate exoplanets discovered with the Kepler observatory has supported a major effort for high resolution imaging of candidate host stars using adaptive optics wave-front correction (AO), speckle imaging and lucky imaging. These images allow examination of the sky as close as a few tenths of an arcsecond from the host stars to detect background objects that might be the source of the Kepler transit signal instead of the host star. This poster reports on the imaging done with AO cameras on the Keck, Palomar 5m and Shane 3m (Lick Observatory) which have been used to obtain high resolution images of over 500 Kepler Object of Interest (KOI) exoplanet candidate host stars. All observations were made at near infrared wavelengths in the J, H and K bands, mostly using the host target star as the AO guide star. Details of the sensitivity to background objects actually attained by these observations and the number of background objects discovered are presented. Implications to the false positive rate of the Kepler candidates are discussed.

Fixed-head star tracker attitude updates on the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Nadelman, Matthew S.; Karl, Jeffrey B.; Hallock, Lou

1994-01-01

The Hubble Space Telescope (HST) was launched in April 1990 to begin observing celestial space to the edge of the universe. National Aeronautics and Space Administration (NASA) standard fixed-head star trackers (FHST's) are used operationally onboard the HST to regularly adjust ('update') the spacecraft attitude before the acquisition of guide stars for science observations. During the first 3 months of the mission, the FHST's updated the spacecraft attitude successfully only 85 percent of the time. During the other periods, the trackers were unable to find the selected stars -- either they failed to find any star, or worse, they selected incorrect stars and produced erroneous attitude updates. In July 1990, the HST project office at Goddard Space Flight Center (GSFC) requested that Computer Sciences Corporation (CSC) form an investigative 'tiger' team to examine these FHST update failures. This paper discusses the work of the FHST tiger team, describes the investigations that led the team to identify the sources of the errors, and defines the solutions that were subsequently developed, which ultimately increased the success rate of FHST updates to approximately 98 percent.

Space-Based Observations of Satellites From the MOST Microsatellite

DTIC Science & Technology

2006-11-01

error estimate for these observations. To perform differential photometry, reference magnitudes for the background stars are needed. The Hubble Guide ...22 6.3 External Calibration References ..................................................................... 23 6.4 Post...32 10. References

Terrestrial Planet Finder Coronagraph 2005: Overview of Technology Development and System Design Studies

NASA Technical Reports Server (NTRS)

Ford, Virginia G.

2005-01-01

Technology research, design trades, and modeling and analysis guide the definition of a Terrestrial Planet Finder Coronagraph Mission that will search for and characterize earth-like planets around near-by stars. Operating in visible wavebands, this mission will use coronagraphy techniques to suppress starlight to enable capturing and imaging the reflected light from a planet orbiting in the habitable zone of its parent star. The light will be spectrally characterized to determine the presence of life-indicating chemistry in the planet atmosphere.

The Black Hole Masses and Star Formation Rates of z>1 Dust Obscured Galaxies: Results from Keck OSIRIS Integral Field Spectroscopy

NASA Astrophysics Data System (ADS)

Melbourne, J.; Peng, Chien Y.; Soifer, B. T.; Urrutia, Tanya; Desai, Vandana; Armus, L.; Bussmann, R. S.; Dey, Arjun; Matthews, K.

2011-04-01

We have obtained high spatial resolution Keck OSIRIS integral field spectroscopy of four z ~ 1.5 ultra-luminous infrared galaxies that exhibit broad Hα emission lines indicative of strong active galactic nucleus (AGN) activity. The observations were made with the Keck laser guide star adaptive optics system giving a spatial resolution of 0farcs1 or <1 kpc at these redshifts. These high spatial resolution observations help to spatially separate the extended narrow-line regions—possibly powered by star formation—from the nuclear regions, which may be powered by both star formation and AGN activity. There is no evidence for extended, rotating gas disks in these four galaxies. Assuming dust correction factors as high as A(Hα) = 4.8 mag, the observations suggest lower limits on the black hole masses of (1-9) × 108 M sun and star formation rates <100 M sun yr-1. The black hole masses and star formation rates of the sample galaxies appear low in comparison to other high-z galaxies with similar host luminosities. We explore possible explanations for these observations, including host galaxy fading, black hole growth, and the shut down of star formation.

Artificial Neural Network-Based Early-Age Concrete Strength Monitoring Using Dynamic Response Signals.

PubMed

Kim, Junkyeong; Lee, Chaggil; Park, Seunghee

2017-06-07

Concrete is one of the most common materials used to construct a variety of civil infrastructures. However, since concrete might be susceptible to brittle fracture, it is essential to confirm the strength of concrete at the early-age stage of the curing process to prevent unexpected collapse. To address this issue, this study proposes a novel method to estimate the early-age strength of concrete, by integrating an artificial neural network algorithm with a dynamic response measurement of the concrete material. The dynamic response signals of the concrete, including both electromechanical impedances and guided ultrasonic waves, are obtained from an embedded piezoelectric sensor module. The cross-correlation coefficient of the electromechanical impedance signals and the amplitude of the guided ultrasonic wave signals are selected to quantify the variation in dynamic responses according to the strength of the concrete. Furthermore, an artificial neural network algorithm is used to verify a relationship between the variation in dynamic response signals and concrete strength. The results of an experimental study confirm that the proposed approach can be effectively applied to estimate the strength of concrete material from the early-age stage of the curing process.

Artificial Neural Network-Based Early-Age Concrete Strength Monitoring Using Dynamic Response Signals

PubMed Central

Kim, Junkyeong; Lee, Chaggil; Park, Seunghee

2017-01-01

Concrete is one of the most common materials used to construct a variety of civil infrastructures. However, since concrete might be susceptible to brittle fracture, it is essential to confirm the strength of concrete at the early-age stage of the curing process to prevent unexpected collapse. To address this issue, this study proposes a novel method to estimate the early-age strength of concrete, by integrating an artificial neural network algorithm with a dynamic response measurement of the concrete material. The dynamic response signals of the concrete, including both electromechanical impedances and guided ultrasonic waves, are obtained from an embedded piezoelectric sensor module. The cross-correlation coefficient of the electromechanical impedance signals and the amplitude of the guided ultrasonic wave signals are selected to quantify the variation in dynamic responses according to the strength of the concrete. Furthermore, an artificial neural network algorithm is used to verify a relationship between the variation in dynamic response signals and concrete strength. The results of an experimental study confirm that the proposed approach can be effectively applied to estimate the strength of concrete material from the early-age stage of the curing process. PMID:28590456

On the search for artificial Dyson-like structures around pulsars

NASA Astrophysics Data System (ADS)

Osmanov, Z.

2016-04-01

Assuming the possibility of existence of a supercivilization we extend the idea of Freeman Dyson considering pulsars instead of stars. It is shown that instead of a spherical shell the supercivilization must use ring-like constructions. We have found that a size of the `ring' should be of the order of (10-4-10-1) AU with temperature interval (300-600) K for relatively slowly rotating pulsars and (10-350) AU with temperature interval (300-700) K for rapidly spinning neutron stars, respectively. Although for the latter the Dyson construction is unrealistically massive and cannot be considered seriously. Analyzing the stresses in terms of the radiation and wind flows it has been argued that they cannot significantly affect the ring construction. On the other hand, the ring in-plane unstable equilibrium can be restored by the energy which is small compared with the energy extracted from the star. This indicates that the search for infrared ring-like sources close to slowly rotating pulsars seems to be quite promising.

An Improved Technique for the Photometry and Astrometry of Faint Companions

NASA Astrophysics Data System (ADS)

Burke, Daniel; Gladysz, Szymon; Roberts, Lewis; Devaney, Nicholas; Dainty, Chris

2009-07-01

We propose a new approach to differential astrometry and photometry of faint companions in adaptive optics images. It is based on a prewhitening matched filter, also referred to in the literature as the Hotelling observer. We focus on cases where the signal of the companion is located within the bright halo of the parent star. Using real adaptive optics data from the 3 m Shane telescope at the Lick Observatory, we compare the performance of the Hotelling algorithm with other estimation algorithms currently used for the same problem. The real single-star data are used to generate artificial binary objects with a range of magnitude ratios. In most cases, the Hotelling observer gives significantly lower astrometric and photometric errors. In the case of high Strehl ratio (SR) data (SR ≈ 0.5), the differential photometry of a binary star with a Δm = 4.5 and a separation of 0.6″ is better than 0.1 mag a factor of 2 lower than the other algorithms considered.

Development of artificial meteor for observation of upper atmosphere

NASA Astrophysics Data System (ADS)

Watanabe, Masaki; Sahara, Hironori; Abe, Shinsuke; Watanabe, Takeo; Nojiri, Yuta; Okajima, Lena

2016-04-01

This study proposes a method for the observation of the upper atmosphere using an artificial meteor injected by a mass driver installed on a microsatellite. The mass driver injects a pill at a velocity of 200 m/s and deorbits it into the atmosphere. The emission of the pill can then be observed from the ground at the necessary time and location. This approach could contribute to a better understanding of the global environment as well as different aspects of astronomy and planetary science. To realize the proposed method, the required size and emission of the pill have to be determined. Therefore, we conducted flow-field simulations, spectroscopic estimations, and an experiment on an artificial meteor in the arc heater wind tunnel at the Institute of Space and Astronautical Science in the Japan Aerospace Exploration Agency (ISAS/JAXA). From the results, we confirmed that the light emission could be observed as a shooting star by the naked eye and thus verified the feasibility of the method.

FIRE's Guide to First-Year Orientation and Thought Reform on Campus. FIRE's Guides to Student Rights on Campus

ERIC Educational Resources Information Center

Silverglate, Harvey A.; Lorence, Jordan

2005-01-01

Before one can have the freedom to express ideas in open debate, however, one must have freedom of conscience: the right to arrive at one's private beliefs, without being coerced into an artificial unity by those who wield power over him/her. After all, the freedom to speak is a dead letter if one lacks the freedom to think, to believe, or to…

MAPPING THE CLUMPY STRUCTURES WITHIN SUBMILLIMETER GALAXIES USING LASER-GUIDE STAR ADAPTIVE OPTICS SPECTROSCOPY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menendez-Delmestre, Karin; Goncalves, Thiago S.; Blain, Andrew W.

2013-04-20

We present the first integral-field spectroscopic observations of high-redshift submillimeter-selected galaxies (SMGs) using Laser-Guide Star Adaptive Optics. We target H{alpha} emission of three SMGs at redshifts z {approx} 1.4-2.4 with the OH-Suppressing Infrared Imaging Spectrograph on Keck. The spatially resolved spectroscopy of these galaxies reveals unresolved broad-H{alpha} line regions (FWHM >1000 km s{sup -1}) likely associated with an active galactic nucleus (AGN) and regions of diffuse star formation traced by narrow-line H{alpha} emission (FWHM {approx}< 500 km s{sup -1}) dominated by multiple H{alpha}-bright stellar clumps, each contributing 1%-30% of the total clump-integrated H{alpha} emission. We find that these SMGs hostmore » high star formation rate surface densities, similar to local extreme sources, such as circumnuclear starbursts and luminous infrared galaxies. However, in contrast to these local environments, SMGs appear to be undergoing such intense activity on significantly larger spatial scales as revealed by extended H{alpha} emission over 4-16 kpc. H{alpha} kinematics show no evidence of ordered global motion as would be found in a disk, but rather large velocity offsets ({approx}few Multiplication-Sign 100 km s{sup -1}) between the distinct stellar clumps. Together with the asymmetric distribution of the stellar clumps around the AGN in these objects, it is unlikely that we are unveiling a clumpy disk structure as has been suggested in other high-redshift populations of star-forming galaxies. The SMG clumps in this sample may correspond to remnants of originally independent gas-rich systems that are in the process of merging, hence triggering the ultraluminous SMG phase.« less

From Cool to Hot F-stars: The Influence of Two Ionization Regions in the Acoustic Oscillations

NASA Astrophysics Data System (ADS)

Brito, Ana; Lopes, Ilídio

2018-02-01

The high-precision data available from the Kepler satellite allows us to study the complex outer convective envelopes of solar-type stars. We use a seismic diagnostic, specialized for investigating the outer layers of solar-type stars, to infer the impact of the ionization processes on the oscillation spectrum, for a sample of Kepler stars. These stars, of spectral type F, cover all of the observational seismic domain of the acoustic oscillation spectrum in solar-type stars. They also cover the range between a cool F-dwarf (∼6000 K) and a hotter F-star (∼6400 K). Our study reveals the existence of two relevant ionization regions. One of these regions, which is located closer to the surface of the star, is commonly associated with the second ionization of helium, although other chemical species also contribute to ionization. The second region, located deeper in the envelope, is linked with the ionization of heavy elements. Specifically, in this study, we analyze the elements carbon, nitrogen, oxygen, neon, and iron. Both regions can be related to the K electronic shell. We show that, while for cooler stars like the Sun, the influence of this second region on the oscillation frequencies is small; in hotter stars, its influence becomes comparable to the influence of the region of the second ionization of helium. This can guide us in the study of the outer layers of F-stars, specifically with the understanding of phenomena related to rotation and magnetic activity in these stars.

KAPAO first light: the design, construction and operation of a low-cost natural guide star adaptive optics system

NASA Astrophysics Data System (ADS)

Severson, Scott A.; Choi, Philip I.; Badham, Katherine E.; Bolger, Dalton; Contreras, Daniel S.; Gilbreth, Blaine N.; Guerrero, Christian; Littleton, Erik; Long, Joseph; McGonigle, Lorcan P.; Morrison, William A.; Ortega, Fernando; Rudy, Alex R.; Wong, Jonathan R.; Spjut, Erik; Baranec, Christoph; Riddle, Reed

2014-07-01

We present the instrument design and first light observations of KAPAO, a natural guide star adaptive optics (AO) system for the Pomona College Table Mountain Observatory (TMO) 1-meter telescope. The KAPAO system has dual science channels with visible and near-infrared cameras, a Shack-Hartmann wavefront sensor, and a commercially available 140-actuator MEMS deformable mirror. The pupil relays are two pairs of custom off-axis parabolas and the control system is based on a version of the Robo-AO control software. The AO system and telescope are remotely operable, and KAPAO is designed to share the Cassegrain focus with the existing TMO polarimeter. We discuss the extensive integration of undergraduate students in the program including the multiple senior theses/capstones and summer assistantships amongst our partner institutions. This material is based upon work supported by the National Science Foundation under Grant No. 0960343.

An adaptive optics package designed for astronomical use with a laser guide star tuned to an absorption line of atomic sodium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salmon, J.T.; Avicola, K.; Brase, J.M.

1994-04-11

We present the design and implementation of a very compact adaptive optic system that senses the return light from a sodium guide-star and controls a deformable mirror and a pointing mirror to compensate atmospheric perturbations in the wavefront. The deformable mirror has 19 electrostrictive actuators and triangular subapertures. The wavefront sensor is a Hartmann sensor with lenslets on triangular centers. The high-bandwidth steering mirror assembly incorporates an analog controller that samples the tilt with an avalanche photodiode quad cell. An {line_integral}/25 imaging leg focuses the light into a science camera that can either obtain long-exposure images or speckle data. Inmore » laboratory tests overall Strehl ratios were improved by a factor of 3 when a mylar sheet was used as an aberrator. The crossover frequency at unity gain is 30 Hz.« less

A conceptual scheme for cophasing across gaps in segmented pupils with a laser guide star Fizeau interferometer

NASA Astrophysics Data System (ADS)

Tuthill, Peter

2016-08-01

Finding and maintaining an accurate cophasing solution for the large primary mirrors which comprise the coming generation of Extremely Large Telescopes has required a significant technological development effort that is still ongoing. Mirrors based on an assembly of a few large segments, such as the Giant Magellan Telescope (GMT - under construction) and the Large Binocular Telescope (LBT - operational) face a particular challenge: elements must be cophased across a gaps ranging from tens of centimeters to meters. Although it is widely believed that laser guide stars are not useful for this specific application, this paper advances a new concept that challenges this orthodoxy. By projecting a Fizeau interference pattern into the sky, and analyzing the form of the backscattered image, it is shown that at least in principle it is possible to cophase across arbitrary gaps.

Research on the compensation of laser launch optics to improve the performance of the LGS spot.

PubMed

Liu, Jie; Wang, Jianli; Wang, Yuning; Tian, Donghe; Zheng, Quan; Lin, Xudong; Wang, Liang; Yang, Qingyun

2018-02-01

To improve the beam quality of the uplink laser, a 37 channel piezo-ceramic deformable mirror was inserted into the laser launch optics to compensate the static aberrations. An interferometer was used as the calibration light source as well as the wavefront sensor to perform closed-loop correction for the moment. About 0.38λ root mean square (rms) aberrations, including the deformable mirror's initial figure error, were compensated, and the residual error was less than 0.07λ rms. Field observations with a 2 m optical telescope demonstrated that the peak intensity value of the laser guide star (LGS) spot increased from 5650 to 7658, and the full width at half-maximum (FWHM) size reduced from 4.07 arcseconds to 3.52 arcseconds. With the compensation, an improved guide star spot can be obtained, which is crucial for the adaptive optics systems of ground-based large telescopes.

Nonlinear oscillations of compact stars in the vicinity of the maximum mass configuration

NASA Astrophysics Data System (ADS)

Brillante, A.; Mishustin, I. N.

2015-07-01

We solve the dynamical GR equations for the spherically symmetric evolution of compact stars in the vicinity of the maximum mass, for which instability sets in according to linear perturbation theory. The calculations are done with the analytical Zeldovich-like EOS P=a≤ft(ρ-ρ_0\\right) and with the TM1 parametrisation of the RMF model. The initial configurations for the dynamical calculations are represented by spherical stars with equilibrium density profile, which are perturbed by either i) an artificially added inward velocity field proportional to the radial coordinate, or ii) a rarefaction corresponding to a static and expanded star. These configurations are evolved using a one-dimensional GR hydro code for ideal and barotropic fluids. Depending on the initial conditions we obtain either stable oscillations or the collapse to a black hole. The minimal amplitude of the perturbation, needed to trigger gravitational collapse is evaluated. The approximate independence of this energy on the type of perturbation is pointed out. At the threshold we find type-I critical behaviour for all stellar models considered and discuss the dependence of the time scaling exponent on the baryon mass and EOS.

ARGOS laser system mechanical design

NASA Astrophysics Data System (ADS)

Deysenroth, M.; Honsberg, M.; Gemperlein, H.; Ziegleder, J.; Raab, W.; Rabien, S.; Barl, L.; Gässler, W.; Borelli, J. L.

2014-07-01

ARGOS, a multi-star adaptive optics system is designed for the wide-field imager and multi-object spectrograph LUCI on the LBT (Large Binocular Telescope). Based on Rayleigh scattering the laser constellation images 3 artificial stars (at 532 nm) per each of the 2 eyes of the LBT, focused at a height of 12 km (Ground Layer Adaptive Optics). The stars are nominally positioned on a circle 2' in radius, but each star can be moved by up to 0.5' in any direction. For all of these needs are following main subsystems necessary: 1. A laser system with its 3 Lasers (Nd:YAG ~18W each) for delivering strong collimated light as for LGS indispensable. 2. The Launch system to project 3 beams per main mirror as a 40 cm telescope to the sky. 3. The Wave Front Sensor with a dichroic mirror. 4. The dichroic mirror unit to grab and interpret the data. 5. A Calibration Unit to adjust the system independently also during day time. 6. Racks + platforms for the WFS units. 7. Platforms and ladders for a secure access. This paper should mainly demonstrate how the ARGOS Laser System is configured and designed to support all other systems.

Investigation on the use of artificial neural networks to overcome the effects of environmental and operational changes on guided waves monitoring

NASA Astrophysics Data System (ADS)

El Mountassir, M.; Yaacoubi, S.; Dahmene, F.

2015-07-01

Intelligent feature extraction and advanced signal processing techniques are necessary for a better interpretation of ultrasonic guided waves signals either in structural health monitoring (SHM) or in nondestructive testing (NDT). Such signals are characterized by at least multi-modal and dispersive components. In addition, in SHM, these signals are closely vulnerable to environmental and operational conditions (EOCs), and can be severely affected. In this paper we investigate the use of Artificial Neural Network (ANN) to overcome these effects and to provide a reliable damage detection method with a minimal of false indications. An experimental case of study (full scale pipe) is presented. Damages sizes have been increased and their shapes modified in different steps. Various parameters such as the number of inputs and the number of hidden neurons were studied to find the optimal configuration of the neural network.

Collapse of differentially rotating neutron stars and cosmic censorship

NASA Astrophysics Data System (ADS)

Giacomazzo, Bruno; Rezzolla, Luciano; Stergioulas, Nikolaos

2011-07-01

We present new results on the dynamics and gravitational-wave emission from the collapse of differentially rotating neutron stars. We have considered a number of polytropic stellar models having different values of the dimensionless angular momentum J/M2, where J and M are the asymptotic angular momentum and mass of the star, respectively. For neutron stars with J/M2<1, i.e. “sub-Kerr” models, we were able to find models that are dynamically unstable and that collapse promptly to a rotating black hole. Both the dynamics of the collapse and the consequent emission of gravitational waves resemble those seen for uniformly rotating stars, although with an overall decrease in the efficiency of gravitational-wave emission. For stellar models with J/M2>1, i.e. “supra-Kerr” models, on the other hand, we were not able to find models that are dynamically unstable and all of the computed supra-Kerr models were found to be far from the stability threshold. For these models a gravitational collapse is possible only after a very severe and artificial reduction of the pressure, which then leads to a torus developing nonaxisymmetric instabilities and eventually contracting to a stable axisymmetric stellar configuration. While this does not exclude the possibility that a naked singularity can be produced by the collapse of a differentially rotating star, it also suggests that cosmic censorship is not violated and that generic conditions for a supra-Kerr progenitor do not lead to a naked singularity.

Simple Activities for Powerful Impact

NASA Astrophysics Data System (ADS)

LaConte, K.; Shupla, C. B.; Dusenbery, P.; Harold, J. B.; Holland, A.

2016-12-01

STEM education is having a transformational impact on libraries across the country. The STAR Library Education Network (STAR_Net) provides free Science-Technology Activities & Resources that are helping libraries to engage their communities in STEM learning experiences. Hear the results of a national 2015 survey of library and STEM professionals and learn what STEM programming is currently in place in public libraries and how libraries approach and implement STEM programs. Experience hands-on space science activities that are being used in library programs with multiple age groups. Through these hands-on activities, learners explore the nature of science and employ science and engineering practices, including developing and using models, planning and carrying out investigations, and engaging in argument from evidence (NGSS Lead States, 2013). Learn how STAR_Net can help you print (free!) mini-exhibits and educator guides. Join STAR_Net's online community and access STEM resources and webinars to work with libraries in your local community.

KSC-2009-1691

NASA Image and Video Library

2009-02-18

CAPE CANAVERAL, Fla. – At the Astrotech payload processing facility in Titusville, Fla., workers help guide the canister segment for NASA's Kepler spacecraft as it is lifted toward workers above. The segment will be added to the stack around Kepler. The "canning" provides protection during the spacecraft's transport to the pad. The liftoff of Kepler aboard a Delta II rocket is currently targeted for 10:48 p.m. EST March 5 from Pad 17-B. Kepler is designed to survey more than 100,000 stars in our galaxy to determine the number of sun-like stars that have Earth-size and larger planets, including those that lie in a star's "habitable zone," a region where liquid water, and perhaps life, could exist. If these Earth-size worlds do exist around stars like our sun, Kepler is expected to be the first to find them and the first to measure how common they are. Photo credit: NASA/Troy Cryder

Galaxy Classification using Machine Learning

NASA Astrophysics Data System (ADS)

Fowler, Lucas; Schawinski, Kevin; Brandt, Ben-Elias; widmer, Nicole

2017-01-01

We present our current research into the use of machine learning to classify galaxy imaging data with various convolutional neural network configurations in TensorFlow. We are investigating how five-band Sloan Digital Sky Survey imaging data can be used to train on physical properties such as redshift, star formation rate, mass and morphology. We also investigate the performance of artificially redshifted images in recovering physical properties as image quality degrades.

An artificial Kepler dichotomy? Implications for the coplanarity of planetary systems

NASA Astrophysics Data System (ADS)

Bovaird, Timothy; Lineweaver, Charles H.

2016-10-01

We challenge the assumptions present in previous efforts to model the ensemble of detected Kepler systems, which require a dichotomous stellar population of `fertile' and `sterile' planet producing stars. We remove the assumption of Rayleigh distributed mutual inclinations between planets and show that the need for two distinct stellar populations disappears when the inner part of planetary disks are assumed to be flat, rather than flared.

[A case of cerebral fat embolism after artificial bone replacement operation for femoral head fracture].

PubMed

Kontani, Satoru; Nakamura, Akinobu; Tokumi, Hiroshi; Hirose, Genjirou

2014-01-01

A 83 years old woman was slipped and injured with right femoral neck fracture. After three days from the fracture, she underwent an artificial head bone replacement operation. Immediately after surgery, she complained of chest discomfort, nausea and dyspnea. A few hours later, she became comatose. Brain CT showed no abnormality and clinical diagnosis of heart failure was made without pulmonary embolism on enhanced chest CT. Magnetic resonance imaging (MRI) of the brain next day showed multiple small patchy hyperintense lesion in bilateral hemispheres on diffusion-weighted images (DWI), producing a "star field pattern''. Based on Criteria of Gurd, this patient had one major criterion and four minor criteria. And according to the Criteria of Schonfeld, this patient had 5 points, consistent with clinical diagnosis of fat embolism. Because of these criteria, she was diagnosed as cerebral fat embolism syndrome. We started supported care and edaravon. Two weeks after surgery, her condition recovered and remaind to stuporous state even six month after surgery. We experienced a typical case of cerebral fat embolism, after bone surgery with diagnostic findings on MRI-DWI. Diagnosis of cerebral fat embolism syndrome requires a history of long bone fracture and/or replacing surgery with typical finding on MRI images, such as "star field pattern''.

Use of Synergistic Interactions to Fabricate Strong, Tough, and Conductive Artificial Nacre Based on Graphene Oxide and Chitosan.

PubMed

Wan, Sijie; Peng, Jingsong; Li, Yuchen; Hu, Han; Jiang, Lei; Cheng, Qunfeng

2015-10-27

Graphene is the strongest and stiffest material, leading to the development of promising applications in many fields. However, the assembly of graphene nanosheets into macrosized nanocomposites for practical applications remains a challenge. Nacre in its natural form sets the "gold standard" for toughness and strength, which serves as a guide to the assembly of graphene nanosheets into high-performance nanocomposites. Here we show the strong, tough, conductive artificial nacre based on graphene oxide through synergistic interactions of hydrogen and covalent bonding. Tensile strength and toughness was 4 and 10 times higher, respectively, than that of natural nacre. The exceptional integrated strong and tough artificial nacre has promising applications in aerospace, artificial muscle, and tissue engineering, especially for flexible supercapacitor electrodes due to its high electrical conductivity. The use of synergistic interactions is a strategy for the development of high-performance nanocomposites.

Artificial Intelligence in Cardiology.

PubMed

Johnson, Kipp W; Torres Soto, Jessica; Glicksberg, Benjamin S; Shameer, Khader; Miotto, Riccardo; Ali, Mohsin; Ashley, Euan; Dudley, Joel T

2018-06-12

Artificial intelligence and machine learning are poised to influence nearly every aspect of the human condition, and cardiology is not an exception to this trend. This paper provides a guide for clinicians on relevant aspects of artificial intelligence and machine learning, reviews selected applications of these methods in cardiology to date, and identifies how cardiovascular medicine could incorporate artificial intelligence in the future. In particular, the paper first reviews predictive modeling concepts relevant to cardiology such as feature selection and frequent pitfalls such as improper dichotomization. Second, it discusses common algorithms used in supervised learning and reviews selected applications in cardiology and related disciplines. Third, it describes the advent of deep learning and related methods collectively called unsupervised learning, provides contextual examples both in general medicine and in cardiovascular medicine, and then explains how these methods could be applied to enable precision cardiology and improve patient outcomes. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Effect of data gaps on correlation dimension computed from light curves of variable stars

NASA Astrophysics Data System (ADS)

George, Sandip V.; Ambika, G.; Misra, R.

2015-11-01

Observational data, especially astrophysical data, is often limited by gaps in data that arises due to lack of observations for a variety of reasons. Such inadvertent gaps are usually smoothed over using interpolation techniques. However the smoothing techniques can introduce artificial effects, especially when non-linear analysis is undertaken. We investigate how gaps can affect the computed values of correlation dimension of the system, without using any interpolation. For this we introduce gaps artificially in synthetic data derived from standard chaotic systems, like the Rössler and Lorenz, with frequency of occurrence and size of missing data drawn from two Gaussian distributions. Then we study the changes in correlation dimension with change in the distributions of position and size of gaps. We find that for a considerable range of mean gap frequency and size, the value of correlation dimension is not significantly affected, indicating that in such specific cases, the calculated values can still be reliable and acceptable. Thus our study introduces a method of checking the reliability of computed correlation dimension values by calculating the distribution of gaps with respect to its size and position. This is illustrated for the data from light curves of three variable stars, R Scuti, U Monocerotis and SU Tauri. We also demonstrate how a cubic spline interpolation can cause a time series of Gaussian noise with missing data to be misinterpreted as being chaotic in origin. This is demonstrated for the non chaotic light curve of variable star SS Cygni, which gives a saturated D2 value, when interpolated using a cubic spline. In addition we also find that a careful choice of binning, in addition to reducing noise, can help in shifting the gap distribution to the reliable range for D2 values.

ANSI-ASQ National Accreditation Board /ACLASS

DTIC Science & Technology

2011-03-28

unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18  Laboratories – ISO / IEC 17025  Inspection...Bodies – ISO / IEC 17020  RMPs – ISO Guide 34 (Reference Materials)  PT Providers – ISO 17043  Product Certifiers – ISO Guide 65  Government...Programs: DoD ELAP, EPA Energy Star, CPSC Toy Safety, NRC, NIST IPV6, NLLAP, NEFAP  TRAINING Programs  Certification Bodies – ISO / IEC 17021

Soldier Quality of Life (Operational) and Readiness at Contingency Base Camps: Insights From Qualitative Interviews

DTIC Science & Technology

2017-03-13

camps and Soldier/small unit readiness to guide the development of a quantitative readiness survey . • During structured interviews, 31 Soldiers...camps and Soldier/small unit readiness to guide the development of a quantitative readiness survey . 11UNCLASSIFIED Click to hear quote Methods...We were rock stars.” 60UNCLASSIFIED • These data are driving the selection of attributes for a future quantitative survey of the link between QoL

GMTIFS: the adaptive optics beam steering mirror for the GMT integral-field spectrograph

NASA Astrophysics Data System (ADS)

Davies, J.; Bloxham, G.; Boz, R.; Bundy, D.; Espeland, B.; Fordham, B.; Hart, J.; Herrald, N.; Nielsen, J.; Sharp, R.; Vaccarella, A.; Vest, C.; Young, P. J.

2016-07-01

To achieve the high adaptive optics sky coverage necessary to allow the GMT Integral-Field Spectrograph (GMTIFS) to access key scientific targets, the on-instrument adaptive-optics wavefront-sensing (OIWFS) system must patrol the full 180 arcsecond diameter guide field passed to the instrument. The OIWFS uses a diffraction limited guide star as the fundamental pointing reference for the instrument. During an observation the offset between the science target and the guide star will change due to sources such as flexure, differential refraction and non-sidereal tracking rates. GMTIFS uses a beam steering mirror to set the initial offset between science target and guide star and also to correct for changes in offset. In order to reduce image motion from beam steering errors to those comparable to the AO system in the most stringent case, the beam steering mirror is set a requirement of less than 1 milliarcsecond RMS. This corresponds to a dynamic range for both actuators and sensors of better than 1/180,000. The GMTIFS beam steering mirror uses piezo-walk actuators and a combination of eddy current sensors and interferometric sensors to achieve this dynamic range and control. While the sensors are rated for cryogenic operation, the actuators are not. We report on the results of prototype testing of single actuators, with the sensors, on the bench and in a cryogenic environment. Specific failures of the system are explained and suspected reasons for them. A modified test jig is used to investigate the option of heating the actuator and we report the improved results. In addition to individual component testing, we built and tested a complete beam steering mirror assembly. Testing was conducted with a point source microscope, however controlling environmental conditions to less than 1 micron was challenging. The assembly testing investigated acquisition accuracy and if there was any un-sensed hysteresis in the system. Finally we present the revised beam steering mirror design based on the outcomes and lessons learnt from this prototyping.

A 1.1-1.9 GHz SETI Survey of the Kepler Field. I. A Search for Narrow-band Emission from Select Targets

NASA Astrophysics Data System (ADS)

Siemion, Andrew P. V.; Demorest, Paul; Korpela, Eric; Maddalena, Ron J.; Werthimer, Dan; Cobb, Jeff; Howard, Andrew W.; Langston, Glen; Lebofsky, Matt; Marcy, Geoffrey W.; Tarter, Jill

2013-04-01

We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T eq > 230 K, stars with five or more detected candidates or stars with a super-Earth (R p < 3 R ⊕) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of ~1.5 × 1021 erg s-1, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be {<}10^{-6}\\ M^{-1}_\\odot. Here we describe our observations, data reduction procedures and results.

Non-contact inline monitoring of thermoplastic CFRP tape quality using air-coupled ultrasound

NASA Astrophysics Data System (ADS)

Essig, W.; Fey, P.; Meiler, S.; Kreutzbruck, M.

2017-02-01

Beginning with the aerospace industry, fiber reinforced plastics have spread towards many applications such as automotive, civil engineering as well as sports and leisure articles. Their superior strength and stiffness to mass ratio made them the number one material for achieving high performance. Especially continuous fiber reinforced plastics allow for the construction of structures which are custom tailored to their mechanical loads by adjusting the paths of the fibers to the loading direction. The two main constituents of CFRP are carbon fibers and matrix. Two possibilities for matrix material exist: thermosetting and thermoplastic matrix. While thermosetting matrix may yield better properties with respect to thermal loads, thermoplasticity opens a wide range of applications due to weldability, shapeability, and compatibility to e.g. injection molded thermoplastic materials. Thin (0.1 mm) thermoplastic continuous fiber CFRP tapes with a width of 100 mm were examined using air-coupled ultrasound. Transducers were arranged in reflection as well as transmission setup. By slanted incidence of the ultrasound on the tape surface, guided waves were excited in the material in fiber direction and perpendicular to the fiber direction. Artificial defects - fiber cuts, matrix cuts, circular holes, low velocity impacts from tool drop, and sharp bends - were produced. Experiments on a stationary tape showed good detectability of all artificial defects by guided waves. Also the effects of variation in material properties, fiber volume content and fiber matrix adhesion being the most relevant, on guided wave propagation were examined, to allow for quality assessment. Guided wave measurements were supported by destructive analysis. Also an apparatus containing one endless loop of CFRP tape was constructed and built to simulate inline testing of CFRP tapes, as it would be employed in a CFRP tape production environment or at a CFRP tape processing facility. The influences of tape conveying speed on detectability of artificial defects as well as material properties were elaborated and recommendations for implementation in production scale inline monitoring are given.

Toward the Development of an Artificial Brain on a Micropatterned and Material-Regulated Biochip by Guiding and Promoting the Differentiation and Neurite Outgrowth of Neural Stem/Progenitor Cells.

PubMed

Liu, Yung-Chiang; Lee, I-Chi; Lei, Kin Fong

2018-02-14

An in vitro model mimicking the in vivo environment of the brain must be developed to study neural communication and regeneration and to obtain an understanding of cellular and molecular responses. In this work, a multilayered neural network was successfully constructed on a biochip by guiding and promoting neural stem/progenitor cell differentiation and network formation. The biochip consisted of 3 × 3 arrays of cultured wells connected with channels. Neurospheroids were cultured on polyelectrolyte multilayer (PEM) films in the culture wells. Neurite outgrowth and neural differentiation were guided and promoted by the micropatterns and the PEM films. After 5 days in culture, a 3 × 3 neural network was constructed on the biochip. The function and the connections of the network were evaluated by immunocytochemistry and impedance measurements. Neurons were generated and produced functional and recyclable synaptic vesicles. Moreover, the electrical connections of the neural network were confirmed by measuring the impedance across the neurospheroids. The current work facilitates the development of an artificial brain on a chip for investigations of electrical stimulations and recordings of multilayered neural communication and regeneration.

Near-infrared image-guided laser ablation of dental decay

NASA Astrophysics Data System (ADS)

Tao, You-Chen; Fried, Daniel

2009-09-01

Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO2 laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO2 laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO2 laser ablation system for the selective removal of dental caries.

Near-infrared image-guided laser ablation of dental decay

PubMed Central

Tao, You-Chen; Fried, Daniel

2009-01-01

Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO2 laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO2 laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO2 laser ablation system for the selective removal of dental caries. PMID:19895146

Near-infrared image-guided laser ablation of dental decay.

PubMed

Tao, You-Chen; Fried, Daniel

2009-01-01

Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO(2) laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO(2) laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO(2) laser ablation system for the selective removal of dental caries.

Massive star formation by accretion. I. Disc accretion

NASA Astrophysics Data System (ADS)

Haemmerlé, L.; Eggenberger, P.; Meynet, G.; Maeder, A.; Charbonnel, C.

2016-01-01

Context. Massive stars likely form by accretion and the evolutionary track of an accreting forming star corresponds to what is called the birthline in the Hertzsprung-Russell (HR) diagram. The shape of this birthline is quite sensitive to the evolution of the entropy in the accreting star. Aims: We first study the reasons why some birthlines published in past years present different behaviours for a given accretion rate. We then revisit the question of the accretion rate, which allows us to understand the distribution of the observed pre-main-sequence (pre-MS) stars in the HR diagram. Finally, we identify the conditions needed to obtain a large inflation of the star along its pre-MS evolution that may push the birthline towards the Hayashi line in the upper part of the HR diagram. Methods: We present new pre-MS models including accretion at various rates and for different initial structures of the accreting core. We compare them with previously published equivalent models. From the observed upper envelope of pre-MS stars in the HR diagram, we deduce the accretion law that best matches the accretion history of most of the intermediate-mass stars. Results: In the numerical computation of the time derivative of the entropy, some treatment leads to an artificial loss of entropy and thus reduces the inflation that the accreting star undergoes along the birthline. In the case of cold disc accretion, the existence of a significant swelling during the accretion phase, which leads to radii ≳ 100 R⊙ and brings the star back to the red part of the HR diagram, depends sensitively on the initial conditions. For an accretion rate of 10-3M⊙ yr-1, only models starting from a core with a significant radiative region evolve back to the red part of the HR diagram. We also obtain that, in order to reproduce the observed upper envelope of pre-MS stars in the HR diagram with an accretion law deduced from the observed mass outflows in ultra-compact HII regions, the fraction of the mass that is accreted onto the star should represent a decreasing fraction of the mass outflows when the mass of the accreting object increases. In other words, the accretion efficiency (mass effectively accreted onto the star with respect to the total in falling matter) decreases when the mass of the star increases.

Intelligence Aid for Evaluating Enemy Courses of Action (ENCOA): Guide for Manual and HP41-C/HP41-CV Calculator Procedures

DTIC Science & Technology

1982-06-01

for use by intellignece analysts in field operations, tactical training, and academic DD I 1473wu EDITION OF f OV 65 IS OBSOLETE UNCLASSIFIED SECURITY...Category Factor t.i Fields of fire 1.2 Cover and concealment 1.0 TERRAIN FACTORS 1. oblt 1.4 Seize/deny key terrain 1.5 Observation 1.o Natural/ artificial ...provisions of terrain. - 1.6 Exploits or accommodates natural and artificial obstacles. 2.0 U.S. FORCE FACTORS *: As related to mission accomplishment

A strategic framework for the development and enhancement of safety culture in the artificial tanning sector in Greece.

PubMed

Petri, Aspasia; Karabetsos, Efthymios

2018-06-08

Herein, the strategic framework for the development and enhancement of safety culture in the artificial tanning sector in Greece is presented. This framework has been designed and promoted by the competent national regulatory authority, which is the Greek Atomic Energy Commission (EEAE). The aim is to ensure a common understanding regarding ultraviolet radiation (UVR) and artificial tanning among the artificial tanning professionals, the stakeholders and the general public. The strategic framework is founded on the international organizations' recommendations, the EU requirements and the relevant technical standards. It is comprised of three autonomous but interconnected components: A) A sunbed operators' e-training course and certification process, B) A code of practice addressed individually to the business owners, the sunbeds operators and the sunbeds users, C) Communication strategies aiming to raise awareness regarding UVR and artificial tanning to all the interested parties. The artificial tanning safety culture framework presented here is the policy option that EEAE undertook and it is embedded in the upcoming legislation and regulations for the provision of artificial tanning services in Greece. EEAE considers that the structure of the artificial tanning safety culture strategic framework will serve as the guide for the development and promotion of relevant safety culture strategic frameworks for the provision of aesthetic/wellness services that utilize other non-ionizing radiation sources, which currently don't exist. © 2018 IOP Publishing Ltd.

Patient behavior and the benefits of artificial intelligence: the perils of "dangerous" literacy and illusory patient empowerment.

PubMed

Schulz, Peter J; Nakamoto, Kent

2013-08-01

Artificial intelligence can provide important support of patient health. However, limits to realized benefits can arise as patients assume an active role in their health decisions. Distinguishing the concepts of health literacy and patient empowerment, we analyze conditions that bias patient use of the Internet and limit access to and impact of artificial intelligence. Improving health literacy in the face of the Internet requires significant guidance. Patients must be directed toward the appropriate tools and also provided with key background knowledge enabling them to use the tools and capitalize on the artificial intelligence technology. Benefits of tools employing artificial intelligence to promote health cannot be realized without recognizing and addressing the patients' desires, expectations, and limitations that impact their Internet behavior. In order to benefit from artificial intelligence, patients need a substantial level of background knowledge and skill in information use-i.e., health literacy. It is critical that health professionals respond to patient search for information on the Internet, first by guiding their search to relevant, authoritative, and responsive sources, and second by educating patients about how to interpret the information they are likely to encounter. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Chemical Evolution and History of Star Formation in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Gustafsson, Bengt

1995-07-01

Large scale processes controlling star formation and nucleosynthesis are fundamental but poorly understood. This is especially true for external galaxies. A detailed study of individual main sequence stars in the LMC Bar is proposed. The LMC is close enough to allow this, has considerable spread in stellar ages and a structure permitting identification of stellar populations and their structural features. The Bar presumably plays a dominant role in the chemical and dynamical evolution of the galaxy. Our knowledge is, at best, based on educated guesses. Still, the major population of the Bar is quite old, and many member stars are relatively evolved. The Bar seems to contain stars similar to those of Intermediate to Extreme Pop II in the Galaxy. We want to study the history of star formation, chemical evolution and initial mass function of the population dominating the Bar. We will use field stars close to the turn off point in the HR diagram. From earlier studies, we know that 250-500 such stars are available for uvby photometry in the PC field. We aim at an accuracy of 0.1 -0.2 dex in Me/H and 25% or better in relative ages. This requires an accuracy of about 0.02 mag in the uvby indices, which can be reached, taking into account errors in calibration, flat fielding, guiding and problems due to crowding. For a study of the luminosity function fainter stars will be included as well. Calibration fields are available in Omega Cen and M 67.

Laser-only Adaptive Optics Achieves Significant Image Quality Gains Compared to Seeing-limited Observations over the Entire Sky

NASA Astrophysics Data System (ADS)

Howard, Ward S.; Law, Nicholas M.; Ziegler, Carl A.; Baranec, Christoph; Riddle, Reed

2018-02-01

Adaptive optics laser guide-star systems perform atmospheric correction of stellar wavefronts in two parts: stellar tip-tilt and high-spatial-order laser correction. The requirement of a sufficiently bright guide star in the field-of-view to correct tip-tilt limits sky coverage. In this paper, we show an improvement to effective seeing without the need for nearby bright stars, enabling full sky coverage by performing only laser-assisted wavefront correction. We used Robo-AO, the first robotic AO system, to comprehensively demonstrate this laser-only correction. We analyze observations from four years of efficient robotic operation covering 15000 targets and 42000 observations, each realizing different seeing conditions. Using an autoguider (or a post-processing software equivalent) and the laser to improve effective seeing independent of the brightness of a target, Robo-AO observations show a 39% ± 19% improvement to effective FWHM, without any tip-tilt correction. We also demonstrate that 50% encircled energy performance without tip-tilt correction remains comparable to diffraction-limited, standard Robo-AO performance. Faint-target science programs primarily limited by 50% encircled energy (e.g., those employing integral field spectrographs placed behind the AO system) may see significant benefits to sky coverage from employing laser-only AO.

An improved non-uniformity correction algorithm and its hardware implementation on FPGA

NASA Astrophysics Data System (ADS)

Rong, Shenghui; Zhou, Huixin; Wen, Zhigang; Qin, Hanlin; Qian, Kun; Cheng, Kuanhong

2017-09-01

The Non-uniformity of Infrared Focal Plane Arrays (IRFPA) severely degrades the infrared image quality. An effective non-uniformity correction (NUC) algorithm is necessary for an IRFPA imaging and application system. However traditional scene-based NUC algorithm suffers the image blurring and artificial ghosting. In addition, few effective hardware platforms have been proposed to implement corresponding NUC algorithms. Thus, this paper proposed an improved neural-network based NUC algorithm by the guided image filter and the projection-based motion detection algorithm. First, the guided image filter is utilized to achieve the accurate desired image to decrease the artificial ghosting. Then a projection-based moving detection algorithm is utilized to determine whether the correction coefficients should be updated or not. In this way the problem of image blurring can be overcome. At last, an FPGA-based hardware design is introduced to realize the proposed NUC algorithm. A real and a simulated infrared image sequences are utilized to verify the performance of the proposed algorithm. Experimental results indicated that the proposed NUC algorithm can effectively eliminate the fix pattern noise with less image blurring and artificial ghosting. The proposed hardware design takes less logic elements in FPGA and spends less clock cycles to process one frame of image.

Stellar Populations in the Central 0.5 pc of the Galaxy. I. A New Method for Constructing Luminosity Functions and Surface-density Profiles

NASA Astrophysics Data System (ADS)

Do, T.; Lu, J. R.; Ghez, A. M.; Morris, M. R.; Yelda, S.; Martinez, G. D.; Wright, S. A.; Matthews, K.

2013-02-01

We present new high angular resolution near-infrared spectroscopic observations of the nuclear star cluster surrounding the Milky Way's central supermassive black hole. Using the integral-field spectrograph OSIRIS on Keck II behind the laser-guide-star adaptive optics system, this spectroscopic survey enables us to separate early-type (young, 4-6 Myr) and late-type (old, >1 Gyr) stars with a completeness of 50% down to K' = 15.5 mag, which corresponds to ~10 M ⊙ for the early-type stars. This work increases the radial extent of reported OSIRIS/Keck measurements by more than a factor of three from 4'' to 14'' (0.16 to 0.56 pc), along the projected disk of young stars. For our analysis, we implement a new method of completeness correction using a combination of star-planting simulations and Bayesian inference. We assign probabilities for the spectral type of every source detected in deep imaging down to K' = 15.5 mag using information from spectra, simulations, number counts, and the distribution of stars. The inferred radial surface-density profiles, Σ(R)vpropR -Γ, for the young stars and late-type giants are consistent with earlier results (Γearly = 0.93 ± 0.09, Γlate = 0.16 ± 0.07). The late-type surface-density profile is approximately flat out to the edge of the survey. While the late-type stellar luminosity function is consistent with the Galactic bulge, the completeness-corrected luminosity function of the early-type stars has significantly more young stars at faint magnitudes compared with previous surveys with similar depth. This luminosity function indicates that the corresponding mass function of the young stars is likely less top-heavy than that inferred from previous surveys.

In search of Nemesis

NASA Technical Reports Server (NTRS)

Carlson, S.; Culler, T.; Muller, R. A.; Tetreault, M.; Perlmutter, S.

1994-01-01

The parallax of all stars of visual magnitude greater than about 6.5 has already been measured. If Nemesis is a main-sequence star 1 parsec away, this requires Nemesis's mass to be less than about 0.4 solar masses. If it were less than about 0.05 solar masses its gravity would be too weak to trigger a comet storm. If Nemesis is on the main sequence, this mass range requires it to be a red dwarf. A red dwarf companion would probably have been missed by standard astronomical surveys. Nearby stars are usually found because they are bright or have high proper motion. However, Nemesis's proper motion would now be 0.01 arcsec/yr, and if it is a red dwarf its magnitude is about 10 - too dim to attract attention. Unfortunately, standard four-color photometry does not distinguish between red dwarfs and giants. So although surveys such as the Dearborn Red Star Catalog list stars by magnitude and spectral type, they do not identify the dwarfs. Every star of the correct spectral type and magnitude must be scrutinized. Our candidate list is a hybrid; candidate red stars are identified in the astrometrically poor Dearborn Red Star Catalog and their positions are corrected using the Hubble Guide Star Catalog. When errors in the Dearborn catalog make it impossible to identify the corresponding Hubble star, the fields are split so that we have one centering on each possible candidate. We are currently scrutinizing 3098 fields, which we believe contain all possible red dwarf candidates in the northern hemisphere. Since our last report the analysis and database software has been completely rebuilt to take advantage of updated hardware, to make the data more accessible, and to implement improved methods of data analysis. The software is now completed and we are eliminating stars every clear night.

A Novel Artificial Intelligence System for Endotracheal Intubation.

PubMed

Carlson, Jestin N; Das, Samarjit; De la Torre, Fernando; Frisch, Adam; Guyette, Francis X; Hodgins, Jessica K; Yealy, Donald M

2016-01-01

Adequate visualization of the glottic opening is a key factor to successful endotracheal intubation (ETI); however, few objective tools exist to help guide providers' ETI attempts toward the glottic opening in real-time. Machine learning/artificial intelligence has helped to automate the detection of other visual structures but its utility with ETI is unknown. We sought to test the accuracy of various computer algorithms in identifying the glottic opening, creating a tool that could aid successful intubation. We collected a convenience sample of providers who each performed ETI 10 times on a mannequin using a video laryngoscope (C-MAC, Karl Storz Corp, Tuttlingen, Germany). We recorded each attempt and reviewed one-second time intervals for the presence or absence of the glottic opening. Four different machine learning/artificial intelligence algorithms analyzed each attempt and time point: k-nearest neighbor (KNN), support vector machine (SVM), decision trees, and neural networks (NN). We used half of the videos to train the algorithms and the second half to test the accuracy, sensitivity, and specificity of each algorithm. We enrolled seven providers, three Emergency Medicine attendings, and four paramedic students. From the 70 total recorded laryngoscopic video attempts, we created 2,465 time intervals. The algorithms had the following sensitivity and specificity for detecting the glottic opening: KNN (70%, 90%), SVM (70%, 90%), decision trees (68%, 80%), and NN (72%, 78%). Initial efforts at computer algorithms using artificial intelligence are able to identify the glottic opening with over 80% accuracy. With further refinements, video laryngoscopy has the potential to provide real-time, direction feedback to the provider to help guide successful ETI.

Solar sailing for radio astronomy and seti: An extrasolar mission to 550 AU

NASA Astrophysics Data System (ADS)

Matloff, Gregory L.

1994-11-01

Current or near-term technology is capable of propelling small payloads to 550 Astronomical Units (AU) on flights of decades duration. Beyond 550 AU, natural or artificial electromagnetic (EM) radiation emitted by galactic objects occulted by the Sun is greatly amplified by solar gravitational focusing. Propulsion systems capable of launching such an extrasolar probe include Jupiter gravity-assist, flat or inflatable solar sails unfurled from parabolic solar orbits sunward of the Earth, and the proton-reflecting 'Magsail'. Best performance for a near-future probe is obtained using the solar sail; a superconducting Magsail has great potential for course-correction purposes. A properly configured solar sail can also serve as a radio telescope and as a solar-energy collector to power the probe's instrumentation. The best direction for the probe's trajectory is towards the galactic anti-center. This is because of the astrophysical interest in amplified EM radiation from the galactic center and the large number of Sunlike stars in the galactic arm. Many of these stars could be surveyed for artificial radio emissions using the proposed probe by astronomers engaged in SETI (Search for ExtraTerrestrial Intelligence). By chance, the anti-galactic-center is not too far from the positions on the celestial sphere of the nearby Sunlike stars Tau Ceti and Epsilon Eridani. This random celestial arrangement increases the potential interest of the proposed mission. While focused on or near the galactic center, the probe could also examine a number of objects of astrophysical interest. These include supernova remnants, HI and HIII regions, and neutron stars or black holes near the galctic center. A number of alternative directions for probes of this type exists. Missions could be flown to sample amplified radio emissions from globular clusters such as M13 and M22 and extra-galactic objects such as the Magellanic Clouds and the Great Spiral Galaxy (M31) in Andromeda. For a number of reasons, the galactic center is superior to these objects, at least for the first flights of the SETI-sail.

Hubble Space Telescope Reduced-Gyro Control Law Design, Implementation, and On-Orbit Performance

NASA Technical Reports Server (NTRS)

Clapp, Brian R.; Ramsey, Patrick R.; Wirzburger, John H.; Smith, Daniel C.; VanArsadall, John C.

2008-01-01

Following gyro failures in April 2001 and April 2003, HST Pointing Control System engineers designed reduced-gyro control laws to extend the spacecraft science mission. The Two-Gyro Science (TGS) and One-Gyro Science (OGS) control laws were designed and implemented using magnetometers, star trackers, and Fine Guidance Sensors in succession to control vehicle rate about the missing gyro axes. Both TGS and OGS have demonstrated on-orbit pointing stability of 7 milli-arcseconds or less, which depends upon the guide star magnitude used by the Fine Guidance Sensor. This paper describes the design, implementation, and on-orbit performance of the TGS and OGS control law fine-pointing modes using Fixed Head Star Trackers and Fine Guidance Sensors, after successfully achieving coarse-pointing control using magnetometers.

VizieR Online Data Catalog: A Finding List of Faint UV-Bright Stars (Lanning+, 1998)

NASA Astrophysics Data System (ADS)

Lanning, H. H.

1997-02-01

The Sandage two-color photographic survey was originally made in support of the UHURU x-ray satellite in order to identify those optical counterparts of the detected x-ray sources found in the galactic plane. During inspection of the plates, however, many UV-bright objects fainter than 10th magnitude were seen in the general field. A larger image in the U filter suggested the possibility of a bluer object as in the case of low-luminosity stars, white dwarfs, novae, CVs, normal early B stars, etc. As these are interesting in themselves, it was decided to publish a catalog for the use of other observers. This multi-color photographic technique has been described, for example, by Haro and Herbig (1955). The survey was concentrated on objects with m(B)~10 or fainter. It employed the Palomar 48-in (Oschin) Schmidt telescope and was centered on the galactic plane with overlapping regions covering the galactic latitudes +- 9 degrees, and extending throughout most of the northern plane (l = 0 deg - 227 deg). Plates were taken by J. Kristian, A.R. Sandage, R.J. Brucato, and Lanning, primarily. The data presented here were found following a careful examination of the plates but it should not be assumed these data represent a complete survey of the fields examined. The categories were roughly calibrated against photoelectric (U-B) measures, but a full scale calibration program, including magnitude effects, etc. was not done. The numerical (U-B) limits of the tables should not therefore be taken precisely. The blue magnitude of the sources in the finding list has been estimated using these photoelectric values as a guide but should be considered accurate to only +- 0.5 mag. due to the difficulty of adjusting to the various plate characteristics. Positions were measured from images retrieved from the Space Telescope Science Institute collection of Guide Star digital plate scans. The accuracy of positions from the Guide Star Catalog images has been estimated to be on the order of 0.2-0.8 arcsec (Russell et al. 1990) Information provided by Bidelman (private communication) resulted in the discovery that 15 positions for objects listed in Paper II were in error. Investigation indicated that an incorrect header was associated with the scan of the Guide Star plate originally archived onto optical disk. The incorrect astrometric solution, based on the use of an incorrect origin point, was subsequently applied in the positional determination when centroiding the object. The average offset for positions in right ascension is 14.17 seconds of time, with no detectable trend in the numbers. The offsets in declination range from +6.56 arcseconds through zero to -6.85 arcseconds as one progresses from west to east across the plate. This is consistent with a rotation being introduced into the bad plate solution. Objects with incorrect positions included Lanning 96, 97, 98, 99, 100, 102, 104, 108, 111, 113, 114, 115, 116, 119, and 122. uv.dat contains the corrected coordinates. (2 data files).

On-Sky Tests of a High-Power Pulsed Laser for Sodium Laser Guide Star Adaptive Optics

NASA Astrophysics Data System (ADS)

Otarola, Angel; Hickson, Paul; Gagné, Ronald; Bo, Yong; Zuo, Junwei; Xie, Shiyong; Feng, Lu; Rochester, Simon; Budker, Dmitry; Shen, Shixia; Xue, Suijian; Min, Li; Wei, Kai; Boyer, Corinne; Ellerbroek, Brent; Hu, Jingyao; Peng, Qinjun; Xu, Zuyan

2016-03-01

We present results of on-sky tests performed in the summer of 2013 to characterize the performance of a prototype high-power pulsed laser for adaptive optics. The laser operates at a pulse repetition rate (PRR) of 600-800Hz, with a 6% duty cycle. Its coupling efficiency was found to be, in the best test case (using 18W of transmitted power), 231±14 photons s-1 sr-1 atom-1 W-1 m2 when circular polarization was employed and 167±17 photons s-1 sr-1 atom-1 W-1 m2 with linear polarization. No improvement was seen when D2b repumping was used, but this is likely due to the relatively large laser guide star (LGS) diameter, typically 10 arcsec or more, which resulted in low irradiance levels. Strong relaxation oscillations were present in the laser output, which have the effect of reducing the coupling efficiency. To better understand the results, a physical modeling was performed using the measured pulse profiles and parameters specific to these tests. The model results, for a 10 arcsec angular size LGS spot, agree well with the observations. When extrapolating the physical model for a sub-arcsecond angular size LGS (typical of what is needed for a successful astronomical guide star), the model predicts that this laser would have a coupling efficiency of 130 photons s-1 sr-1 atom-1 W-1 m2, using circular polarization and D2b repumping, for a LGS diameter of 0.6 arcsec Full Width at Half Maximum (FWHM), and free of relaxation oscillations in the 589 nm laser light.

CT Fluoroscopy-Guided Lung Biopsy with Novel Steerable Biopsy Canula: Ex-Vivo Evaluation in Ventilated Porcine Lung Explants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaefer, Philipp J., E-mail: jp.schaefer@rad.uni-kiel.de; Fabel, Michael; Bolte, Hendrik

2010-08-15

The purpose was to evaluate ex-vivo a prototype of a novel biopsy canula under CT fluoroscopy-guidance in ventilated porcine lung explants in respiratory motion simulations. Using an established chest phantom for porcine lung explants, n = 24 artificial lesions consisting of a fat-wax-Lipiodol mixture (approx. 70HU) were placed adjacent to sensible structures such as aorta, pericardium, diaphragm, bronchus and pulmonary artery. A piston pump connected to a reservoir beneath a flexible silicone reconstruction of a diaphragm simulated respiratory motion by rhythmic inflation and deflation of 1.5 L water. As biopsy device an 18-gauge prototype biopsy canula with a lancet-like, helicallymore » bended cutting edge was used. The artificial lesions were punctured under CT fluoroscopy-guidance (SOMATOM Sensation 64, Siemens, Erlangen, Germany; 30mAs/120 kV/5 mm slice thickness) implementing a dedicated protocol for CT fluoroscopy-guided lung biopsy. The mean-diameter of the artificial lesions was 8.3 {+-} 2.6 mm, and the mean-distance of the phantom wall to the lesions was 54.1 {+-} 13.5 mm. The mean-displacement of the lesions by respiratory motion was 14.1 {+-} 4.0 mm. The mean-duration of CT fluoroscopy was 9.6 {+-} 5.1 s. On a 4-point scale (1 = central; 2 = peripheral; 3 = marginal; 4 = off target), the mean-targeted precision was 1.9 {+-} 0.9. No misplacement of the biopsy canula affecting adjacent structures could be detected. The novel steerable biopsy canula proved to be efficient in the ex-vivo set-up. The chest phantom enabling respiratory motion and the steerable biopsy canula offer a feasible ex-vivo system for evaluating and training CT fluoroscopy-guided lung biopsy adapted to respiratory motion.« less

Monitoring the reflection from an artificial defect in rail track using guided wave ultrasound

NASA Astrophysics Data System (ADS)

Loveday, Philip W.; Taylor, Rebecca M. C.; Long, Craig S.; Ramatlo, Dineo A.

2018-04-01

Guided wave ultrasound has the potential to detect relatively large defects in continuously welded rail track at long range. As monitoring can be performed in near real time it would be acceptable to only detect fairly large cracks provided this is achieved prior to complete rail breakage. Heavy haul rail lines are inspected periodically by conventional ultrasound and sections with even relatively small cracks are removed; therefore, no sizable defects are available to demonstrate monitoring in the presence of realistic environmental operating conditions. Instead, we glued a small mass to the rail to simulate reflection from a crack and monitored the guided wave signals as the glue joint deteriorated over time. Data was collected over a two week period on an operational heavy haul line. A piezoelectric transducer mounted under the head of the rail was used in pulse-echo mode to transmit and receive a mode of propagation with energy confined mainly in the head of the rail. The small mass was attached under the head of the rail, at a distance of 375m from the transducer, using a cyanoacrylate glue, which was not expected to remain intact for long. Pre-processing of the collected signals involved rejection of signals containing train noise, averaging, filtering and dispersion compensation. Reflections from aluminothermic welds were used to stretch and scale the signals to reduce the influence of temperature variations. Singular value decomposition and independent component analysis were then applied to the signals with the aim of separating the reflection caused by the artificial defect from the background signal. The performance of these techniques was compared for different time spans. The reflection from the artificial defect showed unanticipated fluctuations.

Artificial Incoherent Speckles Enable Precision Astrometry and Photometry in High-contrast Imaging

NASA Astrophysics Data System (ADS)

Jovanovic, N.; Guyon, O.; Martinache, F.; Pathak, P.; Hagelberg, J.; Kudo, T.

2015-11-01

State-of-the-art coronagraphs employed on extreme adaptive optics enabled instruments are constantly improving the contrast detection limit for companions at ever-closer separations from the host star. In order to constrain their properties and, ultimately, compositions, it is important to precisely determine orbital parameters and contrasts with respect to the stars they orbit. This can be difficult in the post-coronagraphic image plane, as by definition the central star has been occulted by the coronagraph. We demonstrate the flexibility of utilizing the deformable mirror in the adaptive optics system of the Subaru Coronagraphic Extreme Adaptive Optics system to generate a field of speckles for the purposes of calibration. Speckles can be placed up to 22.5 λ/D from the star, with any position angle, brightness, and abundance required. Most importantly, we show that a fast modulation of the added speckle phase, between 0 and π, during a long science integration renders these speckles effectively incoherent with the underlying halo. We quantitatively show for the first time that this incoherence, in turn, increases the robustness and stability of the adaptive speckles, which will improve the precision of astrometric and photometric calibration procedures. This technique will be valuable for high-contrast imaging observations with imagers and integral field spectrographs alike.

The Planning and Scheduling of HST: Improvements and Enhancements since Launch

NASA Astrophysics Data System (ADS)

Taylor, D. K.; Chance, D. R.; Jordan, I. J. E.; Patterson, A. P.; Stanley, M.; Taylor, D. C.

2001-12-01

The planning and scheduling (P&S) systems used in operating the Hubble Space Telescope (HST) have undergone such substantial and pervasive re-engineering that today they dimly resemble those used when HST was launched. Processes (i.e., software, procedures, networking, etc.) which allow program implementation, the generation of a Long Range Plan (LRP), and the scheduling of science and mission activities have improved drastically in nearly 12 years, resulting in a consistently high observing efficiency, a stable LRP that principal investigators can use, exceptionally clean command loads uplinked to the spacecraft, and the capability of a very fast response time due to onboard anomalies or targets of opportunity. In this presentation we describe many of the systems which comprise the P&S ("front-end") system for HST, how and why they were improved, and what benefits have been realized by either the HST user community or the STScI staff. The systems include the Guide Star System, the Remote Proposal Submission System - 2 (RPS2), Artificial Intelligence (AI) planning tools such as Spike, and the science and mission scheduling software. We also describe how using modern software languages such as Python and better development practices allow STScI staff to do more with HST (e.g., to handle much more science data when ACS is installed) without increasing the cost to HST operations.

Astrophotography Basics: Meteors, Comets, Eclipses, Aurorae, Star Trails. Revised.

ERIC Educational Resources Information Center

Eastman Kodak Co., Rochester, NY.

This pamphlet gives an introduction to the principles of astronomical picture-taking. Chapters included are: (1) "Getting Started" (describing stationary cameras, sky charts and mapping, guided cameras, telescopes, brightness of astronomical subjects, estimating exposure, film selection, camera filters, film processing, and exposure for…

Solar tomography adaptive optics.

PubMed

Ren, Deqing; Zhu, Yongtian; Zhang, Xi; Dou, Jiangpei; Zhao, Gang

2014-03-10

Conventional solar adaptive optics uses one deformable mirror (DM) and one guide star for wave-front sensing, which seriously limits high-resolution imaging over a large field of view (FOV). Recent progress toward multiconjugate adaptive optics indicates that atmosphere turbulence induced wave-front distortion at different altitudes can be reconstructed by using multiple guide stars. To maximize the performance over a large FOV, we propose a solar tomography adaptive optics (TAO) system that uses tomographic wave-front information and uses one DM. We show that by fully taking advantage of the knowledge of three-dimensional wave-front distribution, a classical solar adaptive optics with one DM can provide an extra performance gain for high-resolution imaging over a large FOV in the near infrared. The TAO will allow existing one-deformable-mirror solar adaptive optics to deliver better performance over a large FOV for high-resolution magnetic field investigation, where solar activities occur in a two-dimensional field up to 60'', and where the near infrared is superior to the visible in terms of magnetic field sensitivity.

On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars

NASA Astrophysics Data System (ADS)

Basden, A. G.; Bardou, L.; Bonaccini Calia, D.; Buey, T.; Centrone, M.; Chemla, F.; Gach, J. L.; Gendron, E.; Gratadour, D.; Guidolin, I.; Jenkins, D. R.; Marchetti, E.; Morris, T. J.; Myers, R. M.; Osborn, J.; Reeves, A. P.; Reyes, M.; Rousset, G.; Lombardi, G.; Townson, M. J.; Vidal, F.

2017-04-01

The performance of adaptive optics systems is partially dependent on the algorithms used within the real-time control system to compute wavefront slope measurements. We demonstrate the use of a matched filter algorithm for the processing of elongated laser guide star (LGS) Shack-Hartmann images, using the CANARY adaptive optics instrument on the 4.2 m William Herschel Telescope and the European Southern Observatory Wendelstein LGS Unit placed 40 m away. This algorithm has been selected for use with the forthcoming Thirty Meter Telescope, but until now had not been demonstrated on-sky. From the results of a first observing run, we show that the use of matched filtering improves our adaptive optics system performance, with increases in on-sky H-band Strehl measured up to about a factor of 1.1 with respect to a conventional centre of gravity approach. We describe the algorithm used, and the methods that we implemented to enable on-sky demonstration.

Real-time turbulence profiling with a pair of laser guide star Shack-Hartmann wavefront sensors for wide-field adaptive optics systems on large to extremely large telescopes.

PubMed

Gilles, L; Ellerbroek, B L

2010-11-01

Real-time turbulence profiling is necessary to tune tomographic wavefront reconstruction algorithms for wide-field adaptive optics (AO) systems on large to extremely large telescopes, and to perform a variety of image post-processing tasks involving point-spread function reconstruction. This paper describes a computationally efficient and accurate numerical technique inspired by the slope detection and ranging (SLODAR) method to perform this task in real time from properly selected Shack-Hartmann wavefront sensor measurements accumulated over a few hundred frames from a pair of laser guide stars, thus eliminating the need for an additional instrument. The algorithm is introduced, followed by a theoretical influence function analysis illustrating its impulse response to high-resolution turbulence profiles. Finally, its performance is assessed in the context of the Thirty Meter Telescope multi-conjugate adaptive optics system via end-to-end wave optics Monte Carlo simulations.

Microbial Repopulation Following In Situ STAR Remediation

NASA Astrophysics Data System (ADS)

Gerhard, J.; Overbeeke, G.; Edwards, E.; Lomheim, L.; Grant, G.

2016-12-01

STAR (Self-sustaining Treatment for Active Remediation) is an emerging remediation technology that employs a self-sustaining smouldering reaction to destroy nonaqueous phase liquids (NAPLs) in the subsurface. The reaction front travels outwards from an ignition well at approximately 0.5 per day and subjects the soil to temperatures of 400°C-1000°C. The objectives of this work were to monitor re-saturation of the soil over time and quantify the microbial repopulation of the treated zone. STAR is currently being applied as a full scale, in situ remedy for coal tar beneath a former creosol manufacturing facility in New Jersey, USA. This study analyzed soil cores taken at regular intervals following STAR treatment, allowing time for groundwater to re-infiltrate and for microbial populations to potentially reestablish. Soil and groundwater were analyzed for total number of microorganisms via quantitative Polymerase Chain Reaction (qPCR), as well as microbial diversity via amplicon sequencing. Results demonstrate that microbes rapidly repopulated over a 2 month period to 106 gene copies/g of soil. However, concentrations in the treated zone did not rise above this concentration over 6 months post-STAR, indicating a low carrying capacity of the treated soil. To examine the system in more detail and consider the effects of bio-stimulation, a bench top column study using site soil and artificial groundwater explored the rate at which STAR-treated soil is repopulated with naturally occurring microorganisms in the presence and absence of lactate and a terminal electron acceptor. Results demonstrated that biostimulation did not increase the carrying capacity of the STAR treated sol, but rather shifted the microbial community to reflect the TEA provided, in this case, promoting sulfate reducers. Overall, the work illustrates that microbial populations in STAR treated soil do recover via groundwater infiltration but robust communities will take time to naturally establish.

Radius Determination of Solar-type Stars Using Asteroseismology: What to Expect from the Kepler Mission

NASA Astrophysics Data System (ADS)

Stello, Dennis; Chaplin, William J.; Bruntt, Hans; Creevey, Orlagh L.; García-Hernández, Antonio; Monteiro, Mario J. P. F. G.; Moya, Andrés; Quirion, Pierre-Olivier; Sousa, Sergio G.; Suárez, Juan-Carlos; Appourchaux, Thierry; Arentoft, Torben; Ballot, Jerome; Bedding, Timothy R.; Christensen-Dalsgaard, Jørgen; Elsworth, Yvonne; Fletcher, Stephen T.; García, Rafael A.; Houdek, Günter; Jiménez-Reyes, Sebastian J.; Kjeldsen, Hans; New, Roger; Régulo, Clara; Salabert, David; Toutain, Thierry

2009-08-01

For distant stars, as observed by the NASA Kepler satellite, parallax information is currently of fairly low quality and is not complete. This limits the precision with which the absolute sizes of the stars and their potential transiting planets can be determined by traditional methods. Asteroseismology will be used to aid the radius determination of stars observed during NASA's Kepler mission. We report on the recent asteroFLAG hare-and-hounds Exercise#2, where a group of "hares" simulated data of F-K main-sequence stars that a group of "hounds" sought to analyze, aimed at determining the stellar radii. We investigated stars in the range 9 < V < 15, both with and without parallaxes. We further test different uncertainties in T eff, and compare results with and without using asteroseismic constraints. Based on the asteroseismic large frequency spacing, obtained from simulations of 4 yr time series data from the Kepler mission, we demonstrate that the stellar radii can be correctly and precisely determined, when combined with traditional stellar parameters from the Kepler Input Catalogue. The radii found by the various methods used by each independent hound generally agree with the true values of the artificial stars to within 3%, when the large frequency spacing is used. This is 5-10 times better than the results where seismology is not applied. These results give strong confidence that radius estimation can be performed to better than 3% for solar-like stars using automatic pipeline reduction. Even when the stellar distance and luminosity are unknown we can obtain the same level of agreement. Given the uncertainties used for this exercise we find that the input log g and parallax do not help to constrain the radius, and that T eff and metallicity are the only parameters we need in addition to the large frequency spacing. It is the uncertainty in the metallicity that dominates the uncertainty in the radius.

Is Sucralose Too Good to Be True?

ERIC Educational Resources Information Center

Thomas, Courtney L.

2012-01-01

Student interest in artificial sweeteners can enhance the biochemistry classroom learning experience. This in class, guided-inquiry activity focuses on sucralose and fits into a 50-min biochemistry class for undergraduate science majors. Background knowledge of carbohydrate structure, function, and metabolism as well as familiarity with…

Killer artificial antigen-presenting cells: the synthetic embodiment of a ‘guided missile’

PubMed Central

Schütz, Christian; Oelke, Mathias; Schneck, Jonathan P; Mackensen, Andreas; Fleck, Martin

2010-01-01

At present, the treatment of T-cell-dependent autoimmune diseases relies exclusively on strategies leading to nonspecific suppression of the immune systems causing a substantial reduced ability to control concomitant infections or malignancies. Furthermore, long-term treatment with most drugs is accompanied by several serious adverse effects and does not consequently result in cure of the primary immunological malfunction. By contrast, antigen-specific immunotherapy offers the potential to achieve the highest therapeutic efficiency in accordance with minimal adverse effects. Therefore, several studies have been performed utilizing antigen-presenting cells specifically engineered to deplete allo- or antigen-specific T cells (‘guided missiles’). Many of these strategies take advantage of the Fas/Fas ligand signaling pathway to efficiently induce antigen-presenting cell-mediated apoptosis in targeted T cells. In this article, we discuss the advantages and shortcomings of a novel non-cell-based ‘killer artificial antigen-presenting cell’ strategy, developed to overcome obstacles related to current cell-based approaches for the treatment of T-cell-mediated autoimmunity. PMID:20636007

Kepler Eclipsing Binary Stars. I. Catalog and Principal Characterization of 1879 Eclipsing Binaries in the First Data Release

NASA Astrophysics Data System (ADS)

Prša, Andrej; Batalha, Natalie; Slawson, Robert W.; Doyle, Laurance R.; Welsh, William F.; Orosz, Jerome A.; Seager, Sara; Rucker, Michael; Mjaseth, Kimberly; Engle, Scott G.; Conroy, Kyle; Jenkins, Jon; Caldwell, Douglas; Koch, David; Borucki, William

2011-03-01

The Kepler space mission is devoted to finding Earth-size planets orbiting other stars in their habitable zones. Its large, 105 deg2 field of view features over 156,000 stars that are observed continuously to detect and characterize planet transits. Yet, this high-precision instrument holds great promise for other types of objects as well. Here we present a comprehensive catalog of eclipsing binary stars observed by Kepler in the first 44 days of operation, the data being publicly available through MAST as of 2010 June 15. The catalog contains 1879 unique objects. For each object, we provide its Kepler ID (KID), ephemeris (BJD0, P 0), morphology type, physical parameters (T eff, log g, E(B - V)), the estimate of third light contamination (crowding), and principal parameters (T 2/T 1, q, fillout factor, and sin i for overcontacts, and T 2/T 1, (R 1 + R 2)/a, esin ω, ecos ω, and sin i for detached binaries). We present statistics based on the determined periods and measure the average occurrence rate of eclipsing binaries to be ~1.2% across the Kepler field. We further discuss the distribution of binaries as a function of galactic latitude and thoroughly explain the application of artificial intelligence to obtain principal parameters in a matter of seconds for the whole sample. The catalog was envisioned to serve as a bridge between the now public Kepler data and the scientific community interested in eclipsing binary stars.

The progenitors of stripped-envelope supernovae

NASA Astrophysics Data System (ADS)

Elias-Rosa, N.

2013-05-01

The type Ib/c SNe are those explosions which come from massive star populations, but lack hydrogen and helium. These have been proposed to originate in the explosions of massive Wolf-Rayet stars, and we should easily be able to detect the very luminous, young progenitors if they exist. However, there has not been any detection of progenitors so far. I present the study of two extinguished Type Ic SNe 2003jg and 2004cc. In both cases there is no clear evidence of a direct detection of their progenitors in deep pre-explosion images. Upper limits derived by inserting artificial stars of known brightness at random positions around the progenitor positions (M_v>-8.8 and M_v>-9 magnitudes for the progenitors of SN 2003jg and SN 2004cc, respectively) are brighter than those expected for a massive WC (Wolf-Rayet, carbon-rich) or WO (Wolf-Rayet, oxygen-rich) (e.g., approximately between -3 and -6 in the LMC). Therefore, this is perhaps further evidence that the most massive stars may give rise to black-holes forming SNe, or it is an undetected, compact massive star hidden by a thick dust lane. However the extinction toward these SNe is currently one of the largest known. Even if these results do not directly reveal the nature of the type Ic SN progenitors, they can help to characterize the dusty environment which surrounded the progenitor of the stripped-envelope CC-SNe.

A 1.1-1.9 GHz SETI SURVEY OF THE KEPLER FIELD. I. A SEARCH FOR NARROW-BAND EMISSION FROM SELECT TARGETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siemion, Andrew P. V.; Korpela, Eric; Werthimer, Dan

2013-04-10

We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T{sub eq} > 230 K, stars with five or more detected candidates or stars with a super-Earth (R{sub p} < 3 R{sub Circled-Plus }) in a >50 day orbit. Baseband voltage data across the entire bandmore » between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than {approx}1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of {approx}1.5 Multiplication-Sign 10{sup 21} erg s{sup -1}, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be <10{sup -6} M{sub Sun }{sup -1}. Here we describe our observations, data reduction procedures and results.« less

StarGuides Plus

NASA Astrophysics Data System (ADS)

Heck, A.

StarGuides Plus represents the most comprehensive and accurately validated collection of practical data on organizations involved in astronomy, related space sciences and other related fields. This invaluable reference source (and its companion volume, StarBriefs Plus) should be on the reference shelf of every library, organization or individual with any interest in these areas. The coverage includes relevant universities, scientific committees, institutions, associations, societies, agencies, companies, bibliographic services, data centers, museums, dealers, distributors, funding organizations, journals, manufacturers, meteorological services, national norms & standard institutes, parent associations & societies, publishers, software producers & distributors, and so on. Besides astronomy and associated space sciences, related fields such as aeronautics, aeronomy, astronautics, atmospheric sciences, chemistry, communications, computer sciences, data processing, education, electronics, engineering, energetics, environment, geodesy, geophysics, information handling, management, mathematics, meteorology, optics, physics, remote sensing, and so on, are also covered where appropriate. After some thirty years in continuous compilation, verification and updating, StarGuides Plus currently gathers together some 6,000 entries from 100 countries. The information is presented in a clear, uncluttered manner for direct and easy use. For each entry, all practical data are listed: city, postal and electronic-mail addresses, telephone and fax numbers, URLs for WWW access, foundation years, numbers of members and/or numbers of staff, main activities, publications titles (with frequencies, ISS-Numbers and circulations), names and geographical coordinates of observing sites, names of planetariums, awards (prizes and/or distinctions) granted, etc. The entries are listed alphabetically in each country. An exhaustive index gives a breakdown not only by different designations and acronyms, but also by location and major terms in names. Thematic sub-indices are also provided as well as a list of telephone and telefax national codes. In short, almost anyone involved in any way in the fields of astronomy and related space sciences will find invaluable contact and background information in this volume. All entries have been compiled from data supplied by the listed organizations and all data have been independently verified - making this compilation the most accurate and relevant source available. Link: http://www.wkap.nl/prod/b/1-4020-1926-2

Fluorescent supramolecular micelles for imaging-guided cancer therapy

NASA Astrophysics Data System (ADS)

Sun, Mengmeng; Yin, Wenyan; Dong, Xinghua; Yang, Wantai; Zhao, Yuliang; Yin, Meizhen

2016-02-01

A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth-inhibitory studies reveal a better therapeutic effect of FSMs after CPT encapsulation when compared with the free CPT drug. The multifunctional FSM nanomedicine platform as a nanovehicle has great potential for fluorescence imaging-guided cancer therapy.A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth-inhibitory studies reveal a better therapeutic effect of FSMs after CPT encapsulation when compared with the free CPT drug. The multifunctional FSM nanomedicine platform as a nanovehicle has great potential for fluorescence imaging-guided cancer therapy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00450d

Possible Observational Criteria for Distinguishing Brown Dwarfs From Planets

NASA Technical Reports Server (NTRS)

Black, David C.

1997-01-01

The difference in formation process between binary stars and planetary systems is reflected in their composition, as well as orbital architecture, particularly in their orbital eccentricity as a function of orbital period. It is suggested here that this difference can be used as an observational criterion to distinguish between brown dwarfs and planets. Application of the orbital criterion suggests that, with three possible exceptions, all of the recently discovered substellar companions may be brown dwarfs and not planets. These criterion may be used as a guide for interpretation of the nature of substellar-mass companions to stars in the future.

A Study Guide for the Analysis of Gaia Astrometic Data

NASA Astrophysics Data System (ADS)

van Altena, W. F.

2018-01-01

The purpose of this paper is to enthusiastically support the use of Gaia's data and to suggest an approach for improving our backgrounds so that its data is used in the best possible manner. The principal goals of the Gaia mission are to investigate the origin and subsequent evolution of the Milky Way by mapping the Galaxy to the 20th magnitude and the determination of positions, parallaxes and proper motions of 109 stars. In addition, Gaia is to determine spectroscopic data including the metallicity, distance, extinction and radial velocities for 150× 106 stars brighter than 15th magnitude.

Project Longshot: A mission to Alpha Centauri

NASA Technical Reports Server (NTRS)

West, Curtis; Chamberlain, Sally; Pagan, Neftali; Stevens, Robert

1989-01-01

Project Longshot, an exercise in the Advanced Design Program for Space, had as its destination Alpha Centauri, the closest star system to our own solar system. Alpha Centauri, a trinary star system, is 4.34 light years from earth. Although Project Longshot is impossible based on existing technologies, areas that require further investigation in order to make this feat possible are identified. Three areas where advances in technology are needed are propulsion, data processing for autonomous command and control functions, and reliability. Propulsion, possibly by antimatter annihilation; navigation and navigation aids; reliable hardware and instruments; artificial intelligence to eliminate the need for command telemetry; laser communication; and a reliable, compact, and lightweight power system that converts energy efficiently and reliably present major challenges. Project Longshot promises exciting advances in science and technology and new information concerning the universe.

Using an Iterative Fourier Series Approach in Determining Orbital Elements of Detached Visual Binary Stars

NASA Astrophysics Data System (ADS)

Tupa, Peter R.; Quirin, S.; DeLeo, G. G.; McCluskey, G. E., Jr.

2007-12-01

We present a modified Fourier transform approach to determine the orbital parameters of detached visual binary stars. Originally inspired by Monet (ApJ 234, 275, 1979), this new method utilizes an iterative routine of refining higher order Fourier terms in a manner consistent with Keplerian motion. In most cases, this approach is not sensitive to the starting orbital parameters in the iterative loop. In many cases we have determined orbital elements even with small fragments of orbits and noisy data, although some systems show computational instabilities. The algorithm was constructed using the MAPLE mathematical software code and tested on artificially created orbits and many real binary systems, including Gliese 22 AC, Tau 51, and BU 738. This work was supported at Lehigh University by NSF-REU grant PHY-9820301.

Epistasis analysis using artificial intelligence.

PubMed

Moore, Jason H; Hill, Doug P

2015-01-01

Here we introduce artificial intelligence (AI) methodology for detecting and characterizing epistasis in genetic association studies. The ultimate goal of our AI strategy is to analyze genome-wide genetics data as a human would using sources of expert knowledge as a guide. The methodology presented here is based on computational evolution, which is a type of genetic programming. The ability to generate interesting solutions while at the same time learning how to solve the problem at hand distinguishes computational evolution from other genetic programming approaches. We provide a general overview of this approach and then present a few examples of its application to real data.

VizieR Online Data Catalog: HST VI Photometry of Six LMC Old Globular Clusters (Olsen+ 1998)

NASA Astrophysics Data System (ADS)

Olsen, K. A. G.; Hodge, P. W.; Mateo, M.; Olszewski, E. W.; Schommer, R. A.; Suntzeff, N. B.; Walker, A. R.

1998-11-01

The following tables contain the results of photometry performed on Hubble Space Telescope WFPC2 images of the Large Magellanic Cloud globular clusters NGC 1754, 1835, 1898, 1916, 2005, and 2019. The magnitudes reported here were measured from Planetary Camera F555W and F814W images using DoPHOT (Schechter, Mateo, & Saha 1993) and afterwards transformed to Johnson V/Kron-Cousins I using equation 9 of Holtzman et al. (1995PASP..107.1065H). We carried out photometry on both long (1500 sec combined in F555W, 1800 sec in F814W) and short (40 sec combined in F555W, 60 sec in F814W) exposures. Where the short exposure photometry produced smaller errors, we report those magnitudes in place of those measured from the long exposures. For each star, we give an integer identifier, its x and y pixel position as measured in the F555W PC image, its V and I magnitude, the photometric errors reported by DoPHOT, both the V and I DoPHOT object types (multiplied by 10 if the reported magnitude was measured in the short exposure frame), and a flag if the star was removed during our procedure for statistical field star subtraction. Summary of data reduction and assessment of photometric accuracy: Cosmic ray rejection, correction for the y-dependent CTE effect (Holtzman et al. 1995a), geometric distortion correction, and bad pixel flagging were applied to the images before performing photometry. For the photometry, we used version 2.5 of DoPHOT, modified by Eric Deutsch to handle floating-point images. We found that there were insufficient numbers of bright, isolated stars in the PC frames for producing aperture corrections. Aperture corrections as a function of position in the frame were instead derived using WFPC2 point spread functions kindly provided by Peter Stetson. As these artificially generated aperture corrections agree well with ones derived from isolated stars in the WF chips, we trust that they are reliable to better than 0.05 mag. In agreement with the report of Whitmore & Heyer (1997), we found an offset in mean magnitudes between the short- and long-exposure photometry. We corrected for this effect by adjusting the short-exposure magnitudes to match, on average, those of the long exposures. Finally, we merged the short- and long- exposure lists of photometry as described above and transformed the magnitudes from the WFPC2 system to Johnson V/Kron-Cousins I, applying the Holtzman et al. (1995PASP..107.1065H) zero points. Statistical field star subtraction was performed using color-magnitude diagrams of the field stars produced from the combined WF frames. Completeness and random and systematic errors in the photometry were extensively modelled through artificial star tests. Crowding causes the completeness to be a strong function of position in the frame, with detection being most difficult near the cluster centers. In addition, we found that crowding introduces systematic errors in the photometry, generally <0.05 mag, that depend on the V-I and V of the star. Fortunately, these errors are well-understood. However, unknown errors in the zero points may persist at the ~0.05 mag level. (5 data files).

VizieR Online Data Catalog: HST VI Photometry of Six LMC Old Globular Clusters (Olsen+ 1998)

NASA Astrophysics Data System (ADS)

Olsen, K. A. G.; Hodge, P. W.; Mateo, M.; Olszewski, E. W.; Schommer, R. A.; Suntzeff, N. B.; Walker, A. R.

1998-11-01

The following tables contain the results of photometry performed on Hubble Space Telescope WFPC2 images of the Large Magellanic Cloud globular clusters NGC 1754, 1835, 1898, 1916, 2005, and 2019. The magnitudes reported here were measured from Planetary Camera F555W and F814W images using DoPHOT (Schechter, Mateo, & Saha 1993) and afterwards transformed to Johnson V/Kron-Cousins I using equation 9 of Holtzman et al. (1995PASP..107.1065H). We carried out photometry on both long (1500 sec combined in F555W, 1800 sec in F814W) and short (40 sec combined in F555W, 60 sec in F814W) exposures. Where the short exposure photometry produced smaller errors, we report those magnitudes in place of those measured from the long exposures. For each star, we give an integer identifier, its x and y pixel position as measured in the F555W PC image, its V and I magnitude, the photometric errors reported by DoPHOT, both the V and I DoPHOT object types (multiplied by 10 if the reported magnitude was measured in the short exposure frame), and a flag if the star was removed during our procedure for statistical field star subtraction. Summary of data reduction and assessment of photometric accuracy: Cosmic ray rejection, correction for the y-dependent CTE effect (Holtzman et al. 1995a), geometric distortion correction, and bad pixel flagging were applied to the images before performing photometry. For the photometry, we used version 2.5 of DoPHOT, modified by Eric Deutsch to handle floating-point images. We found that there were insufficient numbers of bright, isolated stars in the PC frames for producing aperture corrections. Aperture corrections as a function of position in the frame were instead derived using WFPC2 point spread functions kindly provided by Peter Stetson. As these artificially generated aperture corrections agree well with ones derived from isolated stars in the WF chips, we trust that they are reliable to better than 0.05 mag. In agreement with the report of Whitmore & Heyer (1997), we found an offset in mean magnitudes between the short- and long-exposure photometry. We corrected for this effect by adjusting the short-exposure magnitudes to match, on average, those of the long exposures. Finally, we merged the short- and long- exposure lists of photometry as described above and transformed the magnitudes from the WFPC2 system to Johnson V/Kron-Cousins I, applying the Holtzman et al. (1995PASP..107.1065H) zero points. Statistical field star subtraction was performed using color-magnitude diagrams of the field stars produced from the combined WF frames. Completeness and random and systematic errors in the photometry were extensively modelled through artificial star tests. Crowding causes the completeness to be a strong function of position in the frame, with detection being most difficult near the cluster centers. In addition, we found that crowding introduces systematic errors in the photometry, generally <0.05 mag, that depend on the V-I and V of the star. Fortunately, these errors are well-understood. However, unknown errors in the zero points may persist at the ~0.05 mag level. (6 data files).

Predicting the locations of possible long-lived low-mass first stars: importance of satellite dwarf galaxies

NASA Astrophysics Data System (ADS)

Magg, Mattis; Hartwig, Tilman; Agarwal, Bhaskar; Frebel, Anna; Glover, Simon C. O.; Griffen, Brendan F.; Klessen, Ralf S.

2018-02-01

The search for metal-free stars has so far been unsuccessful, proving that if there are surviving stars from the first generation, they are rare, they have been polluted or we have been looking in the wrong place. To predict the likely location of Population III (Pop III) survivors, we semi-analytically model early star formation in progenitors of Milky Way-like galaxies and their environments. We base our model on merger trees from the high-resolution dark matter only simulation suite Caterpillar. Radiative and chemical feedback are taken into account self-consistently, based on the spatial distribution of the haloes. Our results are consistent with the non-detection of Pop III survivors in the Milky Way today. We find that possible surviving Pop III stars are more common in Milky Way satellites than in the main Galaxy. In particular, low-mass Milky Way satellites contain a much larger fraction of Pop III stars than the Milky Way. Such nearby, low-mass Milky Way satellites are promising targets for future attempts to find Pop III survivors, especially for high-resolution, high signal-to-noise spectroscopic observations. We provide the probabilities of finding a Pop III survivor in the red giant branch phase for all known Milky Way satellites to guide future observations.

Young Stellar Populations in MYStIX Star-forming Regions: Candidate Protostars

NASA Astrophysics Data System (ADS)

Romine, Gregory; Feigelson, Eric D.; Getman, Konstantin V.; Kuhn, Michael A.; Povich, Matthew S.

2016-12-01

The Massive Young Star-Forming Complex in Infrared and X-ray (MYStIX) project provides a new census on stellar members of massive star-forming regions within 4 kpc. Here the MYStIX Infrared Excess catalog and Chandra-based X-ray photometric catalogs are mined to obtain high-quality samples of Class I protostars using criteria designed to reduce extragalactic and Galactic field star contamination. A total of 1109 MYStIX Candidate Protostars (MCPs) are found in 14 star-forming regions. Most are selected from protoplanetary disk infrared excess emission, but 20% are found from their ultrahard X-ray spectra from heavily absorbed magnetospheric flare emission. Two-thirds of the MCP sample is newly reported here. The resulting samples are strongly spatially associated with molecular cores and filaments on Herschel far-infrared maps. This spatial agreement and other evidence indicate that the MCP sample has high reliability with relatively few “false positives” from contaminating populations. But the limited sensitivity and sparse overlap among the infrared and X-ray subsamples indicate that the sample is very incomplete with many “false negatives.” Maps, tables, and source descriptions are provided to guide further study of star formation in these regions. In particular, the nature of ultrahard X-ray protostellar candidates without known infrared counterparts needs to be elucidated.

Measuring the stellar luminosity function and spatial density profile of the inner 0.5 pc of the Milky Way nuclear star cluster

NASA Astrophysics Data System (ADS)

Do, Tuan; Ghez, Andrea; Lu, Jessica R.; Morris, Mark R.; Yelda, Sylvana; Martinez, Gregory D.; Peter, Annika H. G.; Wright, Shelley; Bullock, James; Kaplinghat, Manoj; Matthews, K.

2012-07-01

We report on measurements of the luminosity function of early (young) and late-type (old) stars in the central 0.5 pc of the Milky Way nuclear star cluster as well as the density profiles of both components. The young (~ 6 Myr) and old stars (> 1 Gyr) in this region provide different physical probes of the environment around a supermassive black hole; the luminosity function of the young stars offers us a way to measure the initial mass function from star formation in an extreme environment, while the density profile of the old stars offers us a probe of the dynamical interaction of a star cluster with a massive black hole. The two stellar populations are separated through a near-infrared spectroscopic survey using the integral-field spectrograph OSIRIS on Keck II behind the laser guide star adaptive optics system. This spectroscopic survey is able to separate early-type (young) and late-type (old) stars with a completeness of 50% at K' = 15.5. We describe our method of completeness correction using a combination of star planting simulations and Bayesian inference. The completeness corrected luminosity function of the early-type stars contains significantly more young stars at faint magnitudes compared to previous surveys with similar depth. In addition, by using proper motion and radial velocity measurements along with anisotropic spherical Jeans modeling of the cluster, it is possible to measure the spatial density profile of the old stars, which has been difficult to constrain with number counts alone. The most probable model shows that the spatial density profile, n(r) propto r-γ, to be shallow with γ = 0.4 ± 0.2, which is much flatter than the dynamically relaxed case of γ = 3/2 to 7/4, but does rule out a 'hole' in the distribution of old stars. We show, for the first time, that the spatial density profile, the black hole mass, and velocity anisotropy can be fit simultaneously to obtain a black hole mass that is consistent with that derived from individual orbits of stars at distances < 1000 AU from the Galactic center.

Whispering galleries and the control of artificial atoms.

PubMed

Forrester, Derek Michael; Kusmartsev, Feodor V

2016-04-28

Quantum computation using artificial-atoms, such as novel superconducting circuits, can be sensitively controlled by external electromagnetic fields. These fields and the self-fields attributable to the coupled artificial-atoms influence the amount of quantum correlation in the system. However, control elements that can operate without complete destruction of the entanglement of the quantum-bits are difficult to engineer. Here we investigate the possibility of using closely-spaced-linear arrays of metallic-elliptical discs as whispering gallery waveguides to control artificial-atoms. The discs confine and guide radiation through the array with small notches etched into their sides that act as scatterers. We focus on π-ring artificial-atoms, which can generate their own spontaneous fluxes. We find that the micro-discs of the waveguides can be excited by terahertz frequency fields to exhibit whispering-modes and that a quantum-phase-gate composed of π-rings can be operated under their influence. Furthermore, we gauge the level of entanglement through the concurrence measure and show that under certain magnetic conditions a series of entanglement sudden-deaths and revivals occur between the two qubits. This is important for understanding the stability and life-time of qubit operations using, for example, a phase gate in a hybrid of quantum technologies composed of control elements and artificial-atoms.

First Aid Instruction Course.

ERIC Educational Resources Information Center

Bureau of Mines (Dept. of Interior), Washington, DC.

Prepared by the Department of the Interior, this teaching guide is for the instructors' use in teaching a first aid course. Six fundamental areas include: (1) Artificial Respiration, (2) Control of Bleeding, (3) Physical Shock, (4) Open Wounds, Closed Wounds, and Burns, (5) Fractures and Dislocations, and (6) Transportation. A complete…

Intelligent Frameworks for Instructional Design.

ERIC Educational Resources Information Center

Spector, J. Michael; And Others

Many researchers are attempting to develop automated instructional development systems to guide subject matter experts through the lengthy and difficult process of courseware development. Because the targeted users often lack instructional design expertise, a great deal of emphasis has been placed on the use of artificial intelligence (AI) to…

An Automated Approach to Instructional Design Guidance.

ERIC Educational Resources Information Center

Spector, J. Michael; And Others

This paper describes the Guided Approach to Instructional Design Advising (GAIDA), an automated instructional design tool that incorporates techniques of artificial intelligence. GAIDA was developed by the U.S. Air Force Armstrong Laboratory to facilitate the planning and production of interactive courseware and computer-based training materials.…

Stargazing

NASA Astrophysics Data System (ADS)

Moore, Patrick

2000-10-01

On a clear night, the vastness and beauty of the star-filled sky is awe inspiring. In Stargazing: Astronomy without a Telescope Patrick Moore, Britain's best known astronomer, tells you all you need to know about the universe visible to the naked eye. With the aid of charts and illustrations, he explains how to "read" the stars, to know which constellations lie overhead, their trajectory throughout the seasons, and the legends ascribed to them. In a month-by-month guide he describes using detailed star maps of the night skies of both the northern and southern hemispheres. He also takes a look at the planets, the Sun and the Moon and their eclipses, comets, meteors, as well as aurorae and other celestial phenomena--all in accessible scientific detail. This captivating book shows how, even with just the naked eye, astronomy can be a fascinating and rewarding hobby--for life.

Biologically inspired artificial compound eyes.

PubMed

Jeong, Ki-Hun; Kim, Jaeyoun; Lee, Luke P

2006-04-28

This work presents the fabrication of biologically inspired artificial compound eyes. The artificial ommatidium, like that of an insect's compound eyes, consists of a refractive polymer microlens, a light-guiding polymer cone, and a self-aligned waveguide to collect light with a small angular acceptance. The ommatidia are omnidirectionally arranged along a hemispherical polymer dome such that they provide a wide field of view similar to that of a natural compound eye. The spherical configuration of the microlenses is accomplished by reconfigurable microtemplating, that is, polymer replication using the deformed elastomer membrane with microlens patterns. The formation of polymer waveguides self-aligned with microlenses is also realized by a self-writing process in a photosensitive polymer resin. The angular acceptance is directly measured by three-dimensional optical sectioning with a confocal microscope, and the detailed optical characteristics are studied in comparison with a natural compound eye.

User's guide to the Octopus computer network (the SHOC manual)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, C.; Thompson, D.; Whitten, G.

1977-07-18

This guide explains how to enter, run, and debug programs on the Octopus network. It briefly describes the network's operation, and directs the reader to other documents for further information. It stresses those service programs that will be most useful in the long run; ''quick'' methods that have little flexibility are not discussed. The Octopus timesharing network gives the user access to four CDC 7600 computers, two CDC STAR computers, and a broad array of peripheral equipment, from any of 800 or so remote terminals. 16 figures, 7 tables.

User's guide to the Octopus computer network (the SHOC manual)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, C.; Thompson, D.; Whitten, G.

1976-10-07

This guide explains how to enter, run, and debug programs on the Octopus network. It briefly describes the network's operation, and directs the reader to other documents for further information. It stresses those service programs that will be most useful in the long run; ''quick'' methods that have little flexibility are not discussed. The Octopus timesharing network gives the user access to four CDC 7600 computers, two CDC STAR computers, and a broad array of peripheral equipment, from any of 800 or so remote terminals. 8 figures, 4 tables.

User's guide to the Octopus computer network (the SHOC manual)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, C.; Thompson, D.; Whitten, G.

1975-06-02

This guide explains how to enter, run, and debug programs on the Octopus network. It briefly describes the network's operation, and directs the reader to other documents for further information. It stresses those service programs that will be most useful in the long run; ''quick'' methods that have little flexibility are not discussed. The Octopus timesharing network gives the user access to four CDC 7600 computers and a broad array of peripheral equipment, from any of 800 remote terminals. Octopus will soon include the Laboratory's STAR-100 computers. 9 figures, 5 tables. (auth)

Adaptive acoustic energy delivery to near and far fields using foldable, tessellated star transducers

NASA Astrophysics Data System (ADS)

Zou, Chengzhe; Harne, Ryan L.

2017-05-01

Methods of guiding acoustic energy arbitrarily through space have long relied on digital controls to meet performance needs. Yet, more recent attention to adaptive structures with unique spatial configurations has motivated mechanical signal processing (MSP) concepts that may not be subjected to the same functional and performance limitations as digital acoustic beamforming counterparts. The periodicity of repeatable structural reconfiguration enabled by origami-inspired tessellated architectures turns attention to foldable platforms as frameworks for MSP development. This research harnesses principles of MSP to study a tessellated, star-shaped acoustic transducer constituent that provides on-demand control of acoustic energy guiding via folding-induced shape reconfiguration. An analytical framework is established to probe the roles of mechanical and acoustic geometry on the far field directivity and near field focusing of sound energy. Following validation by experiments and verification by simulations, parametric studies are undertaken to uncover relations between constituent topology and acoustic energy delivery to arbitrary points in the free field. The adaptations enabled by folding of the star-shaped transducer reveal capability for restricting sound energy to angular regions in the far field while also introducing means to modulate sound energy by three orders-of-magnitude to locations near to the transducer surface. In addition, the modeling philosophy devised here provides a valuable approach to solve general sound radiation problems for foldable, tessellated acoustic transducer constituents of arbitrary geometry.

Evaluation of articulation simulation system using artificial maxillectomy models.

PubMed

Elbashti, M E; Hattori, M; Sumita, Y I; Taniguchi, H

2015-09-01

Acoustic evaluation is valuable for guiding the treatment of maxillofacial defects and determining the effectiveness of rehabilitation with an obturator prosthesis. Model simulations are important in terms of pre-surgical planning and pre- and post-operative speech function. This study aimed to evaluate the acoustic characteristics of voice generated by an articulation simulation system using a vocal tract model with or without artificial maxillectomy defects. More specifically, we aimed to establish a speech simulation system for maxillectomy defect models that both surgeons and maxillofacial prosthodontists can use in guiding treatment planning. Artificially simulated maxillectomy defects were prepared according to Aramany's classification (Classes I-VI) in a three-dimensional vocal tract plaster model of a subject uttering the vowel /a/. Formant and nasalance acoustic data were analysed using Computerized Speech Lab and the Nasometer, respectively. Formants and nasalance of simulated /a/ sounds were successfully detected and analysed. Values of Formants 1 and 2 for the non-defect model were 675.43 and 976.64 Hz, respectively. Median values of Formants 1 and 2 for the defect models were 634.36 and 1026.84 Hz, respectively. Nasalance was 11% in the non-defect model, whereas median nasalance was 28% in the defect models. The results suggest that an articulation simulation system can be used to help surgeons and maxillofacial prosthodontists to plan post-surgical defects that will be facilitate maxillofacial rehabilitation. © 2015 John Wiley & Sons Ltd.

Binary-corrected velocity dispersions from single- and multi-epoch radial velocities: massive stars in R136 as a test case

NASA Astrophysics Data System (ADS)

Cottaar, M.; Hénault-Brunet, V.

2014-02-01

Orbital motions from binary stars can broaden the observed line-of-sight velocity distribution of a stellar system and artificially inflate the measured line-of-sight velocity dispersion, which can in turn lead to erroneous conclusions about the dynamical state of the system. Recently, a maximum-likelihood procedure was proposed to recover the intrinsic velocity dispersion of a resolved star cluster from a single epoch of radial velocity data of individual stars, which was achieved by simultaneously fitting the intrinsic velocity distribution of the single stars and the centers of mass of the binaries along with the velocity shifts caused by binary orbital motions. Assuming well-characterized binary properties, this procedure can accurately reproduce intrinsic velocity dispersions below 1 km s-1 for solar-type stars. Here we investigate the systematic offsets induced when the binary properties are uncertain and we show that two epochs of radial velocity data with an appropriate baseline can help to mitigate these systematic effects. We first test the method described above using Monte Carlo simulations, taking into account the large uncertainties in the binary properties of OB stars. We then apply it to radial velocity data in the young massive cluster R136 for which the intrinsic velocity dispersion of O-type stars is known from an intensive multi-epoch approach. For typical velocity dispersions of young massive clusters (≳4 km s-1) and with a single epoch of data, we demonstrate that the method can just about distinguish between a cluster in virial equilibrium and an unbound cluster. This is due to the higher spectroscopic binary fraction and more loosely constrained distributions of orbital parameters of OB stars compared to solar-type stars. By extending the maximum-likelihood method to multi-epoch data, we show that the accuracy on the fitted velocity dispersion can be improved by only a few percent by using only two epochs of radial velocities. This procedure offers a promising method of accurately measuring the intrinsic stellar velocity dispersion in other systems for which the binary properties are poorly constrained, for example, young clusters and associations whose luminosity is dominated by OB stars. Appendix A is available in electronic form at http://www.aanda.org

A Question and Answer Guide to Astronomy

NASA Astrophysics Data System (ADS)

Christian, Carol; Roy, Jean-René

2017-03-01

Preface; 1. The sky viewed from Earth; 2. The Earth and Moon system; 3. The Solar System; 4. Stars and stellar systems; 5. Galaxies and the Universe; 6. Life in the Universe; 7. Amateur astronomy; 8. Telescopes and instruments; Unit conversion and basic physical and astronomical measurements; References; Bibliography; Index.

In the Wake of Our Ancestors.

ERIC Educational Resources Information Center

Low, Sam

2003-01-01

To understand and revive the ancient Hawaiian culture, the crew of a traditional Polynesian double-hulled voyaging canoe sails among the Pacific Islands without charts or instruments. Trained by Western science, elders, and experience, the navigator guides the craft by the stars and dead reckoning. Each voyage is linked to Hawaiian classroom…

Hawaii: Navigating a Different Way of Knowing.

ERIC Educational Resources Information Center

Thuermer, Kitty

1999-01-01

Seafarer Nainoa Thompson proved Western scientists wrong when they claimed his Pacific Island ancestors lacked the navigational skills to make their 2,500 mile trans-Pacific voyages, guided only by the stars and the sea. In the same way, schools must model different, more affiliative ways of gaining and imparting knowledge. (MLH)

Hypertext Publishing and the Revitalization of Knowledge.

ERIC Educational Resources Information Center

Louie, Steven; Rubeck, Robert F.

1989-01-01

Discusses the use of hypertext for publishing and other document control activities in higher education. Topics discussed include a model of hypertext, called GUIDE, that is used at the University of Arizona Medical School; the increase in the number of scholarly publications; courseware development by faculty; and artificial intelligence. (LRW)

Bioethics in the Hunger Games

ERIC Educational Resources Information Center

Cook, Kristin; Keller, Donna; Myers, Alyce

2014-01-01

In this guided inquiry, students investigate advantages and disadvantages of genetic engineering by integrating popular fiction into their study of bioethics. What are the effects of artificially created hybrid creatures on characters in "The Hunger Games" and in our society? What are the effects on and basic rights of the organisms…

Evolution of a Rapidly Learned Representation for Speech.

ERIC Educational Resources Information Center

Nakisa, Ramin Charles; Plunkett, Kim

1998-01-01

Describes a connectionist model accounting for newborn infants' ability to finely discriminate almost all human speech contrasts and the fact that their phonemic category boundaries are identical, even for phonemes outside their target language. The model posits an innately guided learning in which an artificial neural network is stored in a…

The first US Naval Observatory CCD Astrograph Catalog

NASA Astrophysics Data System (ADS)

Germain, M. E.; Zacharias, N.; Urban, S. E.; Rafferty, T. J.; Holdenried, E. R.; Zacharias, M. I.; Hall, D. M.; Wycoff, G. L.; Monet, D. G.

2000-05-01

The USNO CCD Astrograph Catalog (UCAC) project is a high precision, astrometric survey of stars having R magnitudes between 7th and 16th. The positional accuracy is 20 mas for stars between 9th and 14th, and 70 mas for fainter stars. This gives a density (stars per square degree) higher than that of the Guide Star Catalog (GSC), with an improvement in positional accuracy of about a factor of ten. Observations began in January 1998 at Cerro Tololo Inter--American Observatory (CTIO) using a five-element 0.2 meter astrograph equipped with a 4k by 4k CCD. The instrument will be moved north in early 2001, and full sky coverage is expected by early 2003. A preliminary catalog (UCAC1) of positions and proper motions of 27 million stars has been constructed which is available on CD-ROM from USNO. Observations between 13 Feb 1998 and 07 Nov 1999 are included with a total of over 79,000 CCD frames covering 80% of the Southern Hemisphere. The catalog is on the International Celestial Reference System (ICRS), which is consistent with J2000. Proper motions of bright stars (V <= 12.5) were derived using a combination of ground-based astrometric catalogs, Hipparcos, and Tycho-2 positions, giving a typical error of 3 mas/yr. For the fainter stars the USNO A2.0 (Monet, 1998) was used as first epoch, with typical proper motion errors of 10 to 15 mas/yr. External comparisons with Tycho-2 and the Yale Southern Proper Motion (SPM) 2.0 data reveal systematic errors to be only on the 10 mas level.

Lucky imaging multiplicity studies of exoplanet host stars

NASA Astrophysics Data System (ADS)

Ginski, C.; Mugrauer, M.; Neuhäuser, R.

2014-03-01

The multiplicity of stars is an important parameter in order to understand star and planet formation. In the past decades extrasolar planets have been discovered around more than 600 stars with the radial velocity and transit techniques. Many of these systems present extreme cases of massive planetary objects at very close separations to their primary stars. To explain the configurations of such systems is hence a continued challenge in the development of formation theories. It will be very interesting to determine if there are significant differences between planets in single and multiple star systems. In our ongoing study we use high resolution imaging techniques to clarify the multiplicity status of nearby (within 250 pc) planet host stars. For targets on the northern hemisphere we employ the lucky imaging instrument Astralux at the 2.2 m telescope of the Calar Alto Observatory. The lucky imaging approach consists of taking several thousand short images with integration times shorter than the speckle coherence time, to sample the speckle variations during the observation window. We then only choose the so called "lucky shots" with a very high Strehl ratio in one of the speckles, to shift and add, resulting in a final image with the highest possible Strehl ratio and therefore highest possible angular resolution. We will present recent results of our study at the Calar Alto Observatory, as well as observations undertaken with the RTK camera at the 20 cm guiding telescope in our own observatory in Großschwabhausen.

A Three-dimensional Simulation of a Magnetized Accretion Disk: Fast Funnel Accretion onto a Weakly Magnetized Star

NASA Astrophysics Data System (ADS)

Takasao, Shinsuke; Tomida, Kengo; Iwasaki, Kazunari; Suzuki, Takeru K.

2018-04-01

We present the results of a global, three-dimensional magnetohydrodynamics simulation of an accretion disk with a rotating, weakly magnetized central star. The disk is threaded by a weak, large-scale poloidal magnetic field, and the central star has no strong stellar magnetosphere initially. Our simulation investigates the structure of the accretion flows from a turbulent accretion disk onto the star. The simulation reveals that fast accretion onto the star at high latitudes occurs even without a stellar magnetosphere. We find that the failed disk wind becomes the fast, high-latitude accretion as a result of angular momentum exchange mediated by magnetic fields well above the disk, where the Lorentz force that decelerates the rotational motion of gas can be comparable to the centrifugal force. Unlike the classical magnetospheric accretion scenario, fast accretion streams are not guided by magnetic fields of the stellar magnetosphere. Nevertheless, the accretion velocity reaches the free-fall velocity at the stellar surface due to the efficient angular momentum loss at a distant place from the star. This study provides a possible explanation why Herbig Ae/Be stars whose magnetic fields are generally not strong enough to form magnetospheres also show indications of fast accretion. A magnetically driven jet is not formed from the disk in our model. The differential rotation cannot generate sufficiently strong magnetic fields for the jet acceleration because the Parker instability interrupts the field amplification.

Mysterious eclipses in the light curve of KIC8462852: a possible explanation

NASA Astrophysics Data System (ADS)

Neslušan, L.; Budaj, J.

2017-04-01

Context. Apart from thousands of "regular" exoplanet candidates, Kepler satellite has discovered a small number of stars exhibiting peculiar eclipse-like events. They are most probably caused by disintegrating bodies transiting in front of the star. However, the nature of the bodies and obscuration events, such as those observed in KIC 8462852, remain mysterious. A swarm of comets or artificial alien mega-structures have been proposed as an explanation for the latter object. Aims: We explore the possibility that such eclipses are caused by the dust clouds associated with massive parent bodies orbiting the host star. Methods: We assumed a massive object and a simple model of the dust cloud surrounding the object. Then, we used the numerical integration to simulate the evolution of the cloud, its parent body, and resulting light-curves as they orbit and transit the star. Results: We found that it is possible to reproduce the basic features in the light-curve of KIC 8462852 with only four objects enshrouded in dust clouds. The fact that they are all on similar orbits and that such models require only a handful of free parameters provides additional support for this hypothesis. Conclusions: This model provides an alternative to the comet scenario. With such physical models at hand, at present, there is no need to invoke alien mega-structures for an explanation of these light-curves.

Structural parameters of young star clusters: fractal analysis

NASA Astrophysics Data System (ADS)

Hetem, A.

2017-07-01

A unified view of star formation in the Universe demand detailed and in-depth studies of young star clusters. This work is related to our previous study of fractal statistics estimated for a sample of young stellar clusters (Gregorio-Hetem et al. 2015, MNRAS 448, 2504). The structural properties can lead to significant conclusions about the early stages of cluster formation: 1) virial conditions can be used to distinguish warm collapsed; 2) bound or unbound behaviour can lead to conclusions about expansion; and 3) fractal statistics are correlated to the dynamical evolution and age. The technique of error bars estimation most used in the literature is to adopt inferential methods (like bootstrap) to estimate deviation and variance, which are valid only for an artificially generated cluster. In this paper, we expanded the number of studied clusters, in order to enhance the investigation of the cluster properties and dynamic evolution. The structural parameters were compared with fractal statistics and reveal that the clusters radial density profile show a tendency of the mean separation of the stars increase with the average surface density. The sample can be divided into two groups showing different dynamic behaviour, but they have the same dynamic evolution, since the entire sample was revealed as being expanding objects, for which the substructures do not seem to have been completely erased. These results are in agreement with the simulations adopting low surface densities and supervirial conditions.

Pattern recognition in the ALFALFA.70 and Sloan Digital Sky Surveys: a catalogue of ˜500 000 H I gas fraction estimates based on artificial neural networks

NASA Astrophysics Data System (ADS)

Teimoorinia, Hossen; Ellison, Sara L.; Patton, David R.

2017-02-01

The application of artificial neural networks (ANNs) for the estimation of H I gas mass fraction (M_{H I}/{{M}_{*}}) is investigated, based on a sample of 13 674 galaxies in the Sloan Digital Sky Survey (SDSS) with H I detections or upper limits from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA). We show that, for an example set of fixed input parameters (g - r colour and I-band surface brightness), a multidimensional quadratic model yields M_{H I}/{{M}_{*}} scaling relations with a smaller scatter (0.22 dex) than traditional linear fits (0.32 dex), demonstrating that non-linear methods can lead to an improved performance over traditional approaches. A more extensive ANN analysis is performed using 15 galaxy parameters that capture variation in stellar mass, internal structure, environment and star formation. Of the 15 parameters investigated, we find that g - r colour, followed by stellar mass surface density, bulge fraction and specific star formation rate have the best connection with M_{H I}/{{M}_{*}}. By combining two control parameters, that indicate how well a given galaxy in SDSS is represented by the ALFALFA training set (PR) and the scatter in the training procedure (σfit), we develop a strategy for quantifying which SDSS galaxies our ANN can be adequately applied to, and the associated errors in the M_{H I}/{{M}_{*}} estimation. In contrast to previous works, our M_{H I}/{{M}_{*}} estimation has no systematic trend with galactic parameters such as M⋆, g - r and star formation rate. We present a catalogue of M_{H I}/{{M}_{*}} estimates for more than half a million galaxies in the SDSS, of which ˜150 000 galaxies have a secure selection parameter with average scatter in the M_{H I}/{{M}_{*}} estimation of 0.22 dex.

Archive eggs: a research and management tool for avian conservation breeding

USGS Publications Warehouse

Smith, Des H.V.; Moehrenschlager, Axel; Christensen, Nancy; Knapik, Dwight; Gibson, Keith; Converse, Sarah J.

2012-01-01

Worldwide, approximately 168 bird species are captive-bred for reintroduction into the wild. Programs tend to be initiated for species with a high level of endangerment. Depressed hatching success can be a problem for such programs and has been linked to artificial incubation. The need for artificial incubation is driven by the practice of multiclutching to increase egg production or by uncertainty over the incubation abilities of captive birds. There has been little attempt to determine how artificial incubation differs from bird-contact incubation. We describe a novel archive (data-logger) egg and use it to compare temperature, humidity, and egg-turning in 5 whooping crane (Grus americana) nests, 4 sandhill crane (G. canadensis) nests, and 3 models of artificial incubator; each of which are used to incubate eggs in whooping crane captive-breeding programs. Mean incubation temperature was 31.7° C for whooping cranes and 32.83° C for sandhill cranes. This is well below that of the artificial incubators (which were set based on a protocol of 37.6° C). Humidity in crane nests varied considerably, but median humidity in all 3 artificial incubators was substantially different from that in the crane nests. Two artificial incubators failed to turn the eggs in a way that mimicked crane egg-turning. Archive eggs are an effective tool for guiding the management of avian conservation breeding programs, and can be custom-made for other species. They also have potential to be applied to research on wild populations.

Isotropic Versus Bipolar Functionalized Biomimetic Artificial Basement Membranes and Their Evaluation in Long-Term Human Cell Co-Culture.

PubMed

Rossi, Angela; Wistlich, Laura; Heffels, Karl-Heinz; Walles, Heike; Groll, Jürgen

2016-08-01

In addition to dividing tissues into compartments, basement membranes are crucial as cell substrates and to regulate cellular behavior. The development of artificial basement membranes is indispensable for the ultimate formation of functional engineered tissues; however, pose a challenge due to their complex structure. Herein, biodegradable electrospun polyester meshes are presented, exhibiting isotropic or bipolar bioactivation as a biomimetic and biofunctional model of the natural basement membrane. In a one-step preparation process, reactive star-shaped prepolymer additives, which generate a hydrophilic fiber surface, are electrospun with cell-adhesion-mediating peptides, derived from major components of the basement membrane. Human skin cells adhere to the functionalized meshes, and long-term co-culture experiments confirm that the artificial basement membranes recapitulate and preserve tissue specific functions. Several layers of immortalized human keratinocytes grow on the membranes, differentiating toward the surface and expressing typical epithelial markers. Fibroblasts migrate into the reticular lamina mimicking part of the mesh. Both cells types begin to produce extracellular matrix proteins and to remodel the initial membrane. It is shown at the example of skin that the artificial basement membrane design provokes biomimetic responses of different cell types and can thus be used as basis for the future development of basement membrane containing tissues. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improving Efficiency in Multi-Strange Baryon Reconstruction in d-Au at STAR

NASA Astrophysics Data System (ADS)

Leight, William

2003-10-01

We report preliminary multi-strange baryon measurements for d-Au collisions recorded at RHIC by the STAR experiment. After using classical topological analysis, in which cuts for each discriminating variable are adjusted by hand, we investigate improvements in signal-to-noise optimization using Linear Discriminant Analysis (LDA). LDA is an algorithm for finding, in the n-dimensional space of the n discriminating variables, the axis on which the signal and noise distributions are most separated. LDA is the first step in moving towards more sophisticated techniques for signal-to-noise optimization, such as Artificial Neural Nets. Due to the relatively low background and sufficiently high yields of d-Au collisions, they form an ideal system to study these possibilities for improving reconstruction methods. Such improvements will be extremely important for forthcoming Au-Au runs in which the size of the combinatoric background is a major problem in reconstruction efforts.

Using Machine Learning To Predict Which Light Curves Will Yield Stellar Rotation Periods

NASA Astrophysics Data System (ADS)

Agüeros, Marcel; Teachey, Alexander

2018-01-01

Using time-domain photometry to reliably measure a solar-type star's rotation period requires that its light curve have a number of favorable characteristics. The probability of recovering a period will be a non-linear function of these light curve features, which are either astrophysical in nature or set by the observations. We employ standard machine learning algorithms (artificial neural networks and random forests) to predict whether a given light curve will produce a robust rotation period measurement from its Lomb-Scargle periodogram. The algorithms are trained and validated using salient statistics extracted from both simulated light curves and their corresponding periodograms, and we apply these classifiers to the most recent Intermediate Palomar Transient Factory (iPTF) data release. With this pipeline, we anticipate measuring rotation periods for a significant fraction of the ∼4x108 stars in the iPTF footprint.

Development of a high-precision selenodetic coordinate system for the physical surface of the Moon based on LED beacons on its surface

NASA Astrophysics Data System (ADS)

Shirenin, A. M.; Mazurova, E. M.; Bagrov, A. V.

2016-11-01

The paper presents a mathematical algorithm for processing an array of angular measurements of light beacons on images of the lunar surface onboard a polar artificial lunar satellite (PALS) during the Luna-Glob mission and coordinate-time referencing of the PALS for the development of reference selenocentric coordinate systems. The algorithm makes it possible to obtain angular positions of point light beacons located on the surface of the Moon in selenocentric celestial coordinates. The operation of measurement systems that determine the position and orientation of the PALS during its active existence have been numerically simulated. Recommendations have been made for the optimal use of different types of measurements, including ground radio trajectory measurements, navigational star sensors based on the onboard star catalog, gyroscopic orientation systems, and space videos of the lunar surface.

Astrometric Search Method for Individually Resolvable Gravitational Wave Sources with Gaia

NASA Astrophysics Data System (ADS)

Moore, Christopher J.; Mihaylov, Deyan P.; Lasenby, Anthony; Gilmore, Gerard

2017-12-01

Gravitational waves (GWs) cause the apparent position of distant stars to oscillate with a characteristic pattern on the sky. Astrometric measurements (e.g., those made by Gaia) provide a new way to search for GWs. The main difficulty facing such a search is the large size of the data set; Gaia observes more than one billion stars. In this Letter the problem of searching for GWs from individually resolvable supermassive black hole binaries using astrometry is addressed for the first time; it is demonstrated how the data set can be compressed by a factor of more than 1 06, with a loss of sensitivity of less than 1%. This technique was successfully used to recover artificially injected GW signals from mock Gaia data and to assess the GW sensitivity of Gaia. Throughout the Letter the complementarity of Gaia and pulsar timing searches for GWs is highlighted.

Rocket instrument for far-UV spectrophotometry of faint astronomical objects.

PubMed

Hartig, G F; Fastie, W G; Davidsen, A F

1980-03-01

A sensitive sounding rocket instrument for moderate (~10-A) resolution far-UV (lambda1160-lambda1750-A) spectrophotometry of faint astronomical objects has been developed. The instrument employs a photon-counting microchannel plate imaging detector and a concave grating spectrograph behind a 40-cm Dall-Kirkham telescope. A unique remote-control pointing system, incorporating an SIT vidicon aspect camera, two star trackers, and a tone-encoded command telemetry link, permits the telescope to be oriented to within 5 arc sec of any target for which suitable guide stars can be found. The design, construction, calibration, and flight performance of the instrument are discussed.

Uprated fine guidance sensor study

NASA Technical Reports Server (NTRS)

1984-01-01

Future orbital observatories will require star trackers of extremely high precision. These sensors must maintain high pointing accuracy and pointing stability simultaneously with a low light level signal from a guide star. To establish the fine guidance sensing requirements and to evaluate candidate fine guidance sensing concepts, the Space Telescope Optical Telescope Assembly was used as the reference optical system. The requirements review was separated into three areas: Optical Telescope Assembly (OTA), Fine Guidance Sensing and astrometry. The results show that the detectors should be installed directly onto the focal surface presented by the optics. This would maximize throughput and minimize point stability error by not incoporating any additional optical elements.

KEPLER ECLIPSING BINARY STARS. I. CATALOG AND PRINCIPAL CHARACTERIZATION OF 1879 ECLIPSING BINARIES IN THE FIRST DATA RELEASE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prsa, Andrej; Engle, Scott G.; Conroy, Kyle

2011-03-15

The Kepler space mission is devoted to finding Earth-size planets orbiting other stars in their habitable zones. Its large, 105 deg{sup 2} field of view features over 156,000 stars that are observed continuously to detect and characterize planet transits. Yet, this high-precision instrument holds great promise for other types of objects as well. Here we present a comprehensive catalog of eclipsing binary stars observed by Kepler in the first 44 days of operation, the data being publicly available through MAST as of 2010 June 15. The catalog contains 1879 unique objects. For each object, we provide its Kepler ID (KID),more » ephemeris (BJD{sub 0}, P{sub 0}), morphology type, physical parameters (T{sub eff}, log g, E(B - V)), the estimate of third light contamination (crowding), and principal parameters (T{sub 2}/T{sub 1}, q, fillout factor, and sin i for overcontacts, and T{sub 2}/T{sub 1}, (R{sub 1} + R{sub 2})/a, esin {omega}, ecos {omega}, and sin i for detached binaries). We present statistics based on the determined periods and measure the average occurrence rate of eclipsing binaries to be {approx}1.2% across the Kepler field. We further discuss the distribution of binaries as a function of galactic latitude and thoroughly explain the application of artificial intelligence to obtain principal parameters in a matter of seconds for the whole sample. The catalog was envisioned to serve as a bridge between the now public Kepler data and the scientific community interested in eclipsing binary stars.« less

High S/N Echelle spectroscopy in young stellar groups. II. Rotational velocities of early-type stars in SCO OB2.

NASA Astrophysics Data System (ADS)

Brown, A. G. A.; Verschueren, W.

1997-03-01

We investigate the rotational velocities of early-type stars in the Sco OB2 association. We measure v.sin(i) for 156 established and probable members of the association. The measurements are performed with three different techniques, which are in increasing order of expected v.sin(i): 1) converting the widths of spectral lines directly to v.sin(i), 2) comparing artificially broadened spectra of low v.sin(i) stars to the target spectrum, 3) comparing the HeI λ4026 line profile to theoretical models. The sample is extended with literature data for 47 established members of Sco OB2. Analysis of the v.sin(i) distributions shows that there are no significant differences between the subgroups of Sco OB2. We find that members of the binary population of Sco OB2 on the whole rotate more slowly than the single stars. In addition, we find that the B7-B9 single star members rotate significantly faster than their B0-B6 counterparts. We test various hypotheses for the distribution of v.sin(i) in the association. The results show that we cannot clearly exclude any form of random distribution of the direction and/or magnitude of the intrinsic rotational velocity vector. We also investigate the effects of rotation on colours in the Walraven photometric system. We show that positions of B7-B9 single dwarfs above the main sequence are a consequence of rotation. This establishes the influence of rotation on the Walraven colours, due primarily to surface gravity effects.

Asteroseismology and mass loss in Be stars. Study with CoRoT

NASA Astrophysics Data System (ADS)

Diago, P. D.

The general aim of this work is the study of Be stars with the CoRoT space mission. The mechanisms responsible of the production and dynamics of the circumstellar gas in Be stars are still not constrained. Observations of non-radial pulsation beating phenomena connected to outbursts point toward a relevance of pulsation, but this mechanism cannot be generalized. In this regard, the observation of classical Be stars with the high-precision CoRoT satellite is providing important keys to understand the physics of these objects and the nature of the Be phenomenon. In order to study the light variations of the selected stars we use photometric and spectroscopic observations. These observations allow us to extract frequencies, amplitudes and phases of these variations. As we will show, these light variations can be connected with pulsations on the stellar surface. For carrying out the frequency analysis we have developed a new code based on standard Fourier analysis. The point is that this code, called PASPER, allows the frequency analysis of large sets of light curves in an automatic mode. This Ph.D. thesis is arranged as follows: In the first three Chapters we describe the scientific framework of this project, giving a brief description on Asteroseismology, presenting the current status of Be stars, and describing the basics of the Fourier analysis and the rudiments of the time series analysis. At the early begin of this Ph.D. thesis, the CoRoT satellite was still on ground getting ready for the launch. In this context, we perform a search for short-period B and Be star variables in the low metallicity environment of the Magellanic Clouds. This study constitutes the Part I of this Ph.D. thesis. This Part has a double goal: i) to test the frequency analysis codes; and ii) to detect observationally beta Cephei and SPB-like B-type pulsators in low metallicity environments, actually not predicted by the pulsational theory and models. This constitutes the PartI. Part II is devoted to the study of Be stars with the CoRoT space mission. Here we depict a complete review on the CoRoT mission. We also describe the results on the analysis of three Be stars from the CoRoT exoplanet field. Finally, we present the results on the frequency analysis of the late Be star HD50209, observed in the seismology field of the \\corot satellite. The analysis of this Be star has revealed up to sixty frequencies, grouped in six different and separated sets, attributed to g-mode pulsations. Finally, we resume the main conclusions of the whole project, including prospects and future work to be done. An addendum with all the published results derived from this project has been added at the end of this Part II. Part III encloses the Appendixes, providing a brief summary of this work in Spanish, a complete description on basic equations of non-radial oscillation, the user guide of the PASPER code and the user guide of the KURTZ_BOS code.

Imaging Transitional Disks with TMT: Lessons Learned from the SEEDS Survey

NASA Technical Reports Server (NTRS)

Grady, Carol A.; Fukagawa, M.; Muto, T.; Hashimoto, J.

2014-01-01

TMT studies of the early phases of giant planet formation will build on studies carried out in this decade using 8-meter class telescopes. One such study is the Strategic Exploration of Exoplanets and Disks with Subaru transitional disk survey. We have found a wealth of indirect signatures of giant planet presence, including spiral arms, pericenter offsets of the outer disk from the star, and changes in disk color at the inner edge of the outer disk in intermediate-mass PMS star disks. T Tauri star transitional disks are less flamboyant, but are also dynamically colder: any spiral arms in these diskswill be more tightly wound. Imaging such features at the distance of the nearest star-forming regions requires higher angular resolution than achieved with HiCIAO+ AO188. Imaging such disks with extreme AO systems requires use of laser guide stars, and are infeasible with the extreme AO systems currently commissioning on 8-meter class telescopes. Similarly, the JWST and AFTAWFIRST coronagraphs being considered have inner working angles 0.2, and will occult the inner 28 atomic units of systems at d140pc, a region where both high-contrast imagery and ALMA data indicate that giant planets are located in transitional disks. However, studies of transitional disks associated with solar-mass stars and their planet complement are feasible with TMT using NFIRAOS.

YOUNG STELLAR POPULATIONS IN MYStIX STAR-FORMING REGIONS: CANDIDATE PROTOSTARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romine, Gregory; Feigelson, Eric D.; Getman, Konstantin V.

The Massive Young Star-Forming Complex in Infrared and X-ray (MYStIX) project provides a new census on stellar members of massive star-forming regions within 4 kpc. Here the MYStIX Infrared Excess catalog and Chandra -based X-ray photometric catalogs are mined to obtain high-quality samples of Class I protostars using criteria designed to reduce extragalactic and Galactic field star contamination. A total of 1109 MYStIX Candidate Protostars (MCPs) are found in 14 star-forming regions. Most are selected from protoplanetary disk infrared excess emission, but 20% are found from their ultrahard X-ray spectra from heavily absorbed magnetospheric flare emission. Two-thirds of the MCP sample ismore » newly reported here. The resulting samples are strongly spatially associated with molecular cores and filaments on Herschel far-infrared maps. This spatial agreement and other evidence indicate that the MCP sample has high reliability with relatively few “false positives” from contaminating populations. But the limited sensitivity and sparse overlap among the infrared and X-ray subsamples indicate that the sample is very incomplete with many “false negatives.” Maps, tables, and source descriptions are provided to guide further study of star formation in these regions. In particular, the nature of ultrahard X-ray protostellar candidates without known infrared counterparts needs to be elucidated.« less

A Daytime Aspect Camera for Balloon Altitudes

NASA Technical Reports Server (NTRS)

Dietz, Kurt L.; Ramsey, Brian D.; Alexander, Cheryl D.; Apple, Jeff A.; Ghosh, Kajal K.; Swift, Wesley R.; Six, N. Frank (Technical Monitor)

2001-01-01

We have designed, built, and flight-tested a new star camera for daytime guiding of pointed balloon-borne experiments at altitudes around 40km. The camera and lens are commercially available, off-the-shelf components, but require a custom-built baffle to reduce stray light, especially near the sunlit limb of the balloon. This new camera, which operates in the 600-1000 nm region of the spectrum, successfully provided daytime aspect information of approximately 10 arcsecond resolution for two distinct star fields near the galactic plane. The detected scattered-light backgrounds show good agreement with the Air Force MODTRAN models, but the daytime stellar magnitude limit was lower than expected due to dispersion of red light by the lens. Replacing the commercial lens with a custom-built lens should allow the system to track stars in any arbitrary area of the sky during the daytime.

Daytime Aspect Camera for Balloon Altitudes

NASA Technical Reports Server (NTRS)

Dietz, Kurt L.; Ramsey, Brian D.; Alexander, Cheryl D.; Apple, Jeff A.; Ghosh, Kajal K.; Swift, Wesley R.

2002-01-01

We have designed, built, and flight-tested a new star camera for daytime guiding of pointed balloon-borne experiments at altitudes around 40 km. The camera and lens are commercially available, off-the-shelf components, but require a custom-built baffle to reduce stray light, especially near the sunlit limb of the balloon. This new camera, which operates in the 600- to 1000-nm region of the spectrum, successfully provides daytime aspect information of approx. 10 arcsec resolution for two distinct star fields near the galactic plane. The detected scattered-light backgrounds show good agreement with the Air Force MODTRAN models used to design the camera, but the daytime stellar magnitude limit was lower than expected due to longitudinal chromatic aberration in the lens. Replacing the commercial lens with a custom-built lens should allow the system to track stars in any arbitrary area of the sky during the daytime.

Methodologic Guide for Evaluating Clinical Performance and Effect of Artificial Intelligence Technology for Medical Diagnosis and Prediction.

PubMed

Park, Seong Ho; Han, Kyunghwa

2018-03-01

The use of artificial intelligence in medicine is currently an issue of great interest, especially with regard to the diagnostic or predictive analysis of medical images. Adoption of an artificial intelligence tool in clinical practice requires careful confirmation of its clinical utility. Herein, the authors explain key methodology points involved in a clinical evaluation of artificial intelligence technology for use in medicine, especially high-dimensional or overparameterized diagnostic or predictive models in which artificial deep neural networks are used, mainly from the standpoints of clinical epidemiology and biostatistics. First, statistical methods for assessing the discrimination and calibration performances of a diagnostic or predictive model are summarized. Next, the effects of disease manifestation spectrum and disease prevalence on the performance results are explained, followed by a discussion of the difference between evaluating the performance with use of internal and external datasets, the importance of using an adequate external dataset obtained from a well-defined clinical cohort to avoid overestimating the clinical performance as a result of overfitting in high-dimensional or overparameterized classification model and spectrum bias, and the essentials for achieving a more robust clinical evaluation. Finally, the authors review the role of clinical trials and observational outcome studies for ultimate clinical verification of diagnostic or predictive artificial intelligence tools through patient outcomes, beyond performance metrics, and how to design such studies. © RSNA, 2018.

Automating individualized coaching and authentic role-play practice for brief intervention training.

PubMed

Hayes-Roth, B; Saker, R; Amano, K

2010-01-01

Brief intervention helps to reduce alcohol abuse, but there is a need for accessible, cost-effective training of clinicians. This study evaluated STAR Workshop , a web-based training system that automates efficacious techniques for individualized coaching and authentic role-play practice. We compared STAR Workshop to a web-based, self-guided e-book and a no-treatment control, for training the Engage for Change (E4C) brief intervention protocol. Subjects were medical and nursing students. Brief written skill probes tested subjects' performance of individual protocol steps, in different clinical scenarios, at three test times: pre-training, post-training, and post-delay (two weeks). Subjects also did live phone interviews with a standardized patient, post-delay. STAR subjects performed significantly better than both other groups. They showed significantly greater improvement from pre-training probes to post-training and post-delay probes. They scored significantly higher on post-delay phone interviews. STAR Workshop appears to be an accessible, cost-effective approach for training students to use the E4C protocol for brief intervention in alcohol abuse. It may also be useful for training other clinical interviewing protocols.

The stellar population and luminosity function in M31 bulge and Inner Disk Fields

NASA Technical Reports Server (NTRS)

Rich, R. Michael; Mould, J. R.; Graham, James R.

1993-01-01

We report infrared photometry and stellar identifications for stars in five fields in the M31 bulge located from 2 to 11 arcmin from the nucleus. These fields have been chosen such that the bulge/disk star ratio predicted from Kent's (1989) small bulge model varies from 7:1 to 1:5, allowing a study of near pure disk and near pure bulge stellar populations. We reject the hypothesis of Davies et al. (1991) that luminous stars found within 500 pc of the nucleus are due to a contaminating disk population. We find that the bulge contains stars in excess of M(sub bol) = -5 mag and that the bulge luminosity function has a distinct shape different from the disk fields. We find many stars redder than (J-K) = 2 mag, and suggest that these stars may be the counterparts of the IRAS-selected Galactic bulge Miras studied by Whitelock et at. (1991). The number of bright stars (M(sub bol) is less than -5 mag) falls off more rapidly than the r band surface brightness. By building model fields out of a bulge luminosity function and artificial stars, we are able to show that the change in the luminosity function toward the center cannot be explained simply by the mismeasurement of overcrowded star images. However, these tests also raise the possibility that the asymptotic giant branch (AGB) tip may be approximately equal to 1 mag fainter than actually measured in our most crowded field, reaching only M(sub bol) = -5. We compare observed counts of AGB stars with those predicted from theoretical lifetimes using a technique of general interest for this problem, the Fuel Consumption Theorem of Renzini & Buzzoni (1986) Spectral Evolution of Galaxies (Reidel, Dordrecht). Our methodology is generally applicable to the study of other resolved extragalactic stellar populations. The number of observed stars per magnitude up to a luminosity of M(bol) = -5.5 mag is consistent with AGB evolution of the whole population of the innermost bulge field with the standard lifetime on the AGB of 1.3 Myr/mag. We advance the possibility that the bulge of M31 may be younger than the oldest Galactic globular clusters. We note that M33 has recently been found to have an r(exp 1/4)-law spheroid consisting of intermediate-age stars; bulges can form later than the old halo population.

RFP tags for labeling secretory pathway proteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Liyang; Zhao, Yanhua; Zhang, Xi

2014-05-09

Highlights: • Membrane protein Orai1 can be used to report the fusion properties of RFPs. • Artificial puncta are affected by dissociation constant as well as pKa of RFPs. • Among tested RFPs mOrange2 is the best choice for secretory protein labeling. - Abstract: Red fluorescent proteins (RFPs) are useful tools for live cell and multi-color imaging in biological studies. However, when labeling proteins in secretory pathway, many RFPs are prone to form artificial puncta, which may severely impede their further uses. Here we report a fast and easy method to evaluate RFPs fusion properties by attaching RFPs to anmore » environment sensitive membrane protein Orai1. In addition, we revealed that intracellular artificial puncta are actually colocalized with lysosome, thus besides monomeric properties, pKa value of RFPs is also a key factor for forming intracellular artificial puncta. In summary, our current study provides a useful guide for choosing appropriate RFP for labeling secretory membrane proteins. Among RFPs tested, mOrange2 is highly recommended based on excellent monomeric property, appropriate pKa and high brightness.« less

On the limitations of statistical absorption studies with the Sloan Digital Sky Surveys I-III

NASA Astrophysics Data System (ADS)

Lan, Ting-Wen; Ménard, Brice; Baron, Dalya; Johnson, Sean; Poznanski, Dovi; Prochaska, J. Xavier; O'Meara, John M.

2018-07-01

We investigate the limitations of statistical absorption measurements with the Sloan Digital Sky Survey (SDSS) optical spectroscopic surveys. We show that changes in the data reduction strategy throughout different data releases have led to a better accuracy at long wavelengths, in particular for sky line subtraction, but a degradation at short wavelengths with the emergence of systematic spectral features with an amplitude of about 1 per cent. We show that these features originate from inaccuracy in the fitting of modelled F-star spectra used for flux calibration. The best-fitting models for those stars are found to systematically overestimate the strength of metal lines and underestimate that of Lithium. We also identify the existence of artefacts due to masking and interpolation procedures at the wavelengths of the hydrogen Balmer series leading to the existence of artificial Balmer α absorption in all SDSS optical spectra. All these effects occur in the rest frame of the standard stars and therefore present Galactic longitude variations due to the rotation of the Galaxy. We demonstrate that the detection of certain weak absorption lines reported in the literature is solely due to calibration effects. Finally, we discuss new strategies to mitigate these issues.

On The Sfr-M* Main Sequence Archetypal Star-Formation History And Analytical Models

NASA Astrophysics Data System (ADS)

Ciesla, Laure; Elbaz, David; Fensch, Jeremy

2017-06-01

From the evolution of the main sequence we can build the star formation history (SFH) of MS galaxies, assuming that they follow this relation all their life. We show that this SFH is not only a function of cosmic time but also involve the seed mass of the galaxy. We discuss the implications of this MS SFH on the stellar mass growth, and the entry in the passive region of the UVJ diagram, while the galaxy is still forming stars. We test the ability of different analytical SFH forms found in the literature to probe the SFR of all type of galaxies. Using a sample of GOODS-South galaxies, we show that these SFHs artificially enhance or create a gradient of age, parallel to the MS. A simple model of a MS galaxy, such as those expected from compaction or variation in gas accretion, undergoing some fluctuations provide does not predict such a gradient, that we show is due to SFH assumptions. We propose an improved analytical form, taking into account a flexibility in the recent SFH that we calibrate as a diagnostic to identify rapidly quenched galaxies from large photometric survey.

On the limitations of statistical absorption studies with the Sloan Digital Sky Surveys I-III

NASA Astrophysics Data System (ADS)

Lan, Ting-Wen; Ménard, Brice; Baron, Dalya; Johnson, Sean; Poznanski, Dovi; Prochaska, J. Xavier; O'Meara, John M.

2018-04-01

We investigate the limitations of statistical absorption measurements with the SDSS optical spectroscopic surveys. We show that changes in the data reduction strategy throughout different data releases have led to a better accuracy at long wavelengths, in particular for sky line subtraction, but a degradation at short wavelengths with the emergence of systematic spectral features with an amplitude of about one percent. We show that these features originate from inaccuracy in the fitting of modeled F-star spectra used for flux calibration. The best-fit models for those stars are found to systematically over-estimate the strength of metal lines and under-estimate that of Lithium. We also identify the existence of artifacts due to masking and interpolation procedures at the wavelengths of the hydrogen Balmer series leading to the existence of artificial Balmer α absorption in all SDSS optical spectra. All these effects occur in the rest-frame of the standard stars and therefore present Galactic longitude variations due to the rotation of the Galaxy. We demonstrate that the detection of certain weak absorption lines reported in the literature are solely due to calibration effects. Finally, we discuss new strategies to mitigate these issues.

Meteor44 Video Meteor Photometry

NASA Technical Reports Server (NTRS)

Swift, Wesley R.; Suggs, Robert M.; Cooke, William J.

2004-01-01

Meteor44 is a software system developed at MSFC for the calibration and analysis of video meteor data. The dynamic range of the (8bit) video data is extended by approximately 4 magnitudes for both meteors and stellar images using saturation compensation. Camera and lens specific saturation compensation coefficients are derived from artificial variable star laboratory measurements. Saturation compensation significantly increases the number of meteors with measured intensity and improves the estimation of meteoroid mass distribution. Astrometry is automated to determine each image s plate coefficient using appropriate star catalogs. The images are simultaneously intensity calibrated from the contained stars to determine the photon sensitivity and the saturation level referenced above the atmosphere. The camera s spectral response is used to compensate for stellar color index and typical meteor spectra in order to report meteor light curves in traditional visual magnitude units. Recent efforts include improved camera calibration procedures, long focal length "streak" meteor photome&y and two-station track determination. Meteor44 has been used to analyze data from the 2001.2002 and 2003 MSFC Leonid observational campaigns as well as several lesser showers. The software is interactive and can be demonstrated using data from recent Leonid campaigns.

Redox-Active Star Molecules Incorporating the 4-Benzoylpyridinium Cation - Implications for the Charge Transfer Along Branches vs. Across the Perimeter in Dendrimer

NASA Technical Reports Server (NTRS)

Leventis, Nicholas; Yang, Jinua; Fabrizio,Even F.; Rawashdeh, Abdel-Monem M.; Oh, Woon Su; Sotiriou-Leventis, Chariklia

2004-01-01

Dendrimers are self-repeating globular branched star molecules, whose fractal structure continues to fascinate, challenge, and inspire. Functional dendrimers may incorporate redox centers, and potential applications include antennae molecules for light harvesting, sensors, mediators, and artificial biomolecules. We report the synthesis and redox properties of four star systems incorporating the 4-benzoyl-N-alkylpyridinium cation; the redox potential varies along the branches but remains constant at fixed radii. Bulk electrolysis shows that at a semi-infinite time scale all redox centers are electrochemically accessible. However, voltammetric analysis (cyclic voltammetry and differential pulse voltammetry) shows that on1y two of the three redox-active centers in the perimeter are electrochemically accessible during potential sweeps as slow as 20 mV/s and as fast as 10 V/s. On the contrary, both redox centers along branches are accessible electrochemically within the same time frame. These results are explained in terms of slow through-space charge transfer and the globular 3-D folding of the molecules and are discussed in terms of their implications on the design of efficient redox functional dendrimers.

Colonizing the Plutoids: The Key to Human Expansion into the Galaxy

NASA Astrophysics Data System (ADS)

Roy, K. I.; Kennedy, R. G.; Fields, D. E.

Pluto-type worlds (plutoids) are far more numerous in our solar system than initially thought with hundreds, maybe thousands, of them existing in the Kuiper belt and Oort cloud. Other stars are likely to also possess many such worlds. These worlds possess almost limitless quantities of water and substantial quantities of nitrogen, which are two limiting ingredients necessary for terraforming planets in the inner solar system. Assuming that faster-than-light travel is impractical, that artificial gravity is only possible via circular motion, that humans remain basically unchanged, and that humanity's expansion into the solar system and beyond is desirable, then exploiting the resources of, and establishing bases and even colonies on, icy plutoids may become essential for human expansion into space. Such colonies face problems involving gravity, radiation, energy supply and complex ecologies. This paper attempts to address those issues and outline what such colonies might look like. This type of colony offers humanity, and perhaps other species, the ability to establish settlements at otherwise undesirable locations, including red and brown dwarf stars. Such colonies could even be established in orphan planets in interstellar space, far from any star.

Multi-approach metabolomics analysis and artificial simplified phytocomplexes reveal cultivar-dependent synergy between polyphenols and ascorbic acid in fruits of the sweet cherry (Prunus avium L.)

PubMed Central

Di Carlo, Flavia; Poletti, Stefania; Bulgarini, Alessandra; Munari, Francesca; Negri, Stefano; Stocchero, Matteo; Ceoldo, Stefania; Avesani, Linda; Assfalg, Michael; Zoccatelli, Gianni; Guzzo, Flavia

2017-01-01

Fruits of the sweet cherry (Prunus avium L.) accumulate a range of antioxidants that can help to prevent cardiovascular disease, inflammation and cancer. We tested the in vitro antioxidant activity of 18 sweet cherry cultivars collected from 12 farms in the protected geographical indication region of Marostica (Vicenza, Italy) during two growing seasons. Multiple targeted and untargeted metabolomics approaches (NMR, LC-MS, HPLC-DAD, HPLC-UV) as well as artificial simplified phytocomplexes representing the cultivars Sandra Tardiva, Sandra and Grace Star were then used to determine whether the total antioxidant activity reflected the additive effects of each compound or resulted from synergistic interactions. We found that the composition of each cultivar depended more on genetic variability than environmental factors. Furthermore, phenolic compounds were the principal source of antioxidant activity and experiments with artificial simplified phytocomplexes indicated strong synergy between the anthocyanins and quercetins/ascorbic acid specifically in the cultivar Sandra Tardiva. Our data therefore indicate that the total antioxidant activity of sweet cherry fruits may originate from cultivar-dependent interactions among different classes of metabolite. PMID:28732012

Stargazing Basics

NASA Astrophysics Data System (ADS)

Kinzer, Paul E.

2015-07-01

Preface; Introduction: why another stargazing guide?; Part I. Stargazing Techniques and Equipment: 1. With the naked eye alone; 2. Binoculars: the next step; 3. 'But I want a telescope!'; Part II. What's up There?: 4. The Solar System; 5. The deep sky; Part III. A Stargazing Glossary: Appendix 1. The Greek alphabet; Appendix 2. The constellations; Some simple star charts; Index.

ASTRONOMY.

ERIC Educational Resources Information Center

Louisiana Arts and Science Center, Baton Rouge.

THIS TEACHER'S GUIDE FOR A UNIT ON ASTRONOMY ESTABLISHES (1) UNDERSTANDINGS AND ATTITUDES, (2) SKILLS, AND (3) CONCEPTS TO BE GAINED IN THE STUDY. THE OVERVIEW EXPLAINS THE ORGANIZATION AND OBJECTIVES OF THE UNIT. TOPICAL DIVISIONS ARE (1) THE EARTH, (2) THE MOON, (3) THE SUN, (4) THE SOLAR SYSTEM, (5) THE STARS, (6) THE UNIVERSE, AND (7) SPACE…

A Ground-based Sensor to Detect GEOs Without the Use of a Laser Guide-star

DTIC Science & Technology

2013-09-01

atmospheric turbulence generator to create atmospheric turbulence. The different Zernikes used in the experiment are focus, astigmatism , and coma...radian of astigmatism in the pupil plane are shown in figure 5. The top row shows actual data obtained with the telescope and the bottom row shows

Theater Battle Management Core System Systems Engineering Case Study

DTIC Science & Technology

2005-02-17

TOC Army Unit TOCs USMC TACC DASC Data Link Data Link AWACS J-STARS Data Link Data Link Data Link RIVET JOINT COMPASS CALL Theater RECCE/SURV Data...Developer’s Guide ( SDG ), Version 2, 30 August 2001. 11. Air Force Electronic Systems Center, ESC/ACF Program Office, ICWG Charter, November 2003. 12

Spatial interferometry in optical astronomy

NASA Technical Reports Server (NTRS)

Gezari, Daniel Y.; Roddier, Francois; Roddier, Claude

1990-01-01

A bibliographic guide is presented to publications of spatial interferometry techniques applied to optical astronomy. Listings appear in alphabetical order, by first author, as well as in specific subject categories listed in chronological order, including imaging theory and speckle interferometry, experimental techniques, and observational results of astronomical studies of stars, the Sun, and the solar system.

A Comparison of Value-Added, Ordinary Least Squares Regression, and the California STAR Accountability Indicators

ERIC Educational Resources Information Center

Black, Aime

2012-01-01

Student achievement to reward or sanction schools. These unadjusted accountability indicators do not account for differences in student or school characteristics that contribute to variations in assessment results. Since the "Coleman Report" (1966), a guiding principle in accountability design has been that educational outcomes data…

Prototype of a laser guide star wavefront sensor for the Extremely Large Telescope

NASA Astrophysics Data System (ADS)

Patti, M.; Lombini, M.; Schreiber, L.; Bregoli, G.; Arcidiacono, C.; Cosentino, G.; Diolaiti, E.; Foppiani, I.

2018-06-01

The new class of large telescopes, like the future Extremely Large Telescope (ELT), are designed to work with a laser guide star (LGS) tuned to a resonance of atmospheric sodium atoms. This wavefront sensing technique presents complex issues when applied to big telescopes for many reasons, mainly linked to the finite distance of the LGS, the launching angle, tip-tilt indetermination and focus anisoplanatism. The implementation of a laboratory prototype for the LGS wavefront sensor (WFS) at the beginning of the phase study of MAORY (Multi-conjugate Adaptive Optics Relay) for ELT first light has been indispensable in investigating specific mitigation strategies for the LGS WFS issues. This paper presents the test results of the LGS WFS prototype under different working conditions. The accuracy within which the LGS images are generated on the Shack-Hartmann WFS has been cross-checked with the MAORY simulation code. The experiments show the effect of noise on centroiding precision, the impact of LGS image truncation on wavefront sensing accuracy as well as the temporal evolution of the sodium density profile and LGS image under-sampling.

STS-88 Mission Insignia

NASA Technical Reports Server (NTRS)

1998-01-01

Designed by the STS-88 crew members, this patch commemorates the first assembly flight to carry United States-built hardware for constructing the International Space Station (ISS). This flight's primary task was to assemble the cornerstone of the Space Station: the Node with the Functional Cargo Block (FGB). The rising sun symbolizes the dawning of a new era of international cooperation in space and the beginning of a new program: the International Space Station. The Earth scene outlines the countries of the Station Partners: the United States, Russia, those of the European Space Agency (ESA), Japan, and Canada. Along with the Pressurized Mating Adapters (PMA) and the Functional Cargo Block, the Node is shown in the final mated configuration while berthed to the Space Shuttle during the STS-88/2A mission. The Big Dipper Constellation points the way to the North Star, a guiding light for pioneers and explorers for generations. In the words of the crew, These stars symbolize the efforts of everyone, including all the countries involved in the design and construction of the International Space Station, guiding us into the future.

International Space Station (ISS)

NASA Image and Video Library

1998-11-08

Designed by the STS-88 crew members, this patch commemorates the first assembly flight to carry United States-built hardware for constructing the International Space Station (ISS). This flight's primary task was to assemble the cornerstone of the Space Station: the Node with the Functional Cargo Block (FGB). The rising sun symbolizes the dawning of a new era of international cooperation in space and the beginning of a new program: the International Space Station. The Earth scene outlines the countries of the Station Partners: the United States, Russia, those of the European Space Agency (ESA), Japan, and Canada. Along with the Pressurized Mating Adapters (PMA) and the Functional Cargo Block, the Node is shown in the final mated configuration while berthed to the Space Shuttle during the STS-88/2A mission. The Big Dipper Constellation points the way to the North Star, a guiding light for pioneers and explorers for generations. In the words of the crew, These stars symbolize the efforts of everyone, including all the countries involved in the design and construction of the International Space Station, guiding us into the future.

KAPAO-Alpha: An On-The-Sky Testbed for Adaptive Optics on Small Aperture Telescopes

NASA Astrophysics Data System (ADS)

Morrison, Will; Choi, P. I.; Severson, S. A.; Spjut, E.; Contreras, D. S.; Gilbreth, B. N.; McGonigle, L. P.; Rudy, A. R.; Xue, A.; Baranec, C.; Riddle, R.

2012-05-01

We present initial in-lab and on-sky results of a natural guide star adaptive optics instrument, KAPAO-Alpha, being deployed on Pomona College’s 1-meter telescope at Table Mountain Observatory. The instrument is an engineering prototype designed to help us identify and solve design and integration issues before building KAPAO, a low-cost, dual-band, natural guide star AO system currently in active development and scheduled for first light in 2013. The Alpha system operates at visible wavelengths, employs Shack-Hartmann wavefront sensing, and is assembled entirely from commercially available components that include: off-the-shelf optics, a 140-actuator BMC deformable mirror, a high speed SciMeasure Lil’ Joe camera, and an EMCCD for science image acquisition. Wavefront reconstruction operating at 1-kHz speeds is handled with a consumer-grade computer running custom software adopted from the Robo-AO project. The assembly and integration of the Alpha instrument has been undertaken as a Pomona College undergraduate thesis. As part of the larger KAPAO project, it is supported by the National Science Foundation under Grant No. 0960343.

Photometric Exoplanet Characterization and Multimedia Astronomy Communication

NASA Astrophysics Data System (ADS)

Cartier, Kimberly M. S.

The transit method of detecting exoplanets has dominated the search for distant worlds since the success of the Kepler space telescope and will continue to lead the field after the launch of the Transiting Exoplanet Survey Satellite in 2018. But detections are just the beginning. Transit light curves can only reveal a limited amount of information about a planet, and that information is almost entirely dependent on the properties of the host star or stars. This dissertation discusses follow-up techniques to more precisely characterize transiting planets using photometric observations. A high-resolution follow-up imaging program using the Hubble Space Telescope (HST) searched for previously unknown stars nearby the hosts of small and cool Kepler exoplanets and observed a higher-than-expected occurrence rate of stellar multiplicity. The rate of previously unknown stellar multiples has strong implications for the size and habitability of the orbiting planets. Three systems with newly discovered stellar multiplicity, Kepler-296 (2 stars, 5 planets), KOI-2626 (3 stars, 1 planet), and KOI-3049 (2 stars, 1 planet), were characterized in more detail. In the cases of Kepler-296 and KOI-2626, some of the planets lost their previous habitable zone status because of host star ambiguity. Next, the ultra-short period, ultra-hot Jupiter WASP-103b was used as a casestudy to test for the presence of a stratospheric temperature inversion through dayside emission spectroscopy using HST. WASP-103b's near-infrared emission spectrum is consistent with an isothermal or thermally-inverted atmosphere and shows no significant broadband water absorption feature. Detection of an anomalously strong "super- Rayleigh" slope in its optical transmission spectrum prompted follow-up transmission spectroscopy of WASP-103b's atmosphere using the MINiature Radial Velocity Array (MINERVA), which tentatively verified the unexplained "super-Rayleigh" spectral slope. The final follow-up technique for transiting planets presented in this work quantifies the information contained in a sequence of transit depths using a normalized information content metric. The normalized information content metric can distinguish between naturally occurring, regular transits of real exoplanets detected via Kepler (low information content) and simulated artificial beacons whose depth and timing vary in a prime number sequence (high information content). Highly variable transit sequences with natural explanations--as seen with KIC 12557548, for example--can only be distinguished from artificial beacons when observed at a high signal-to-noise ratio (moderate information content) and may otherwise be confused with a more information-rich sequence. This dissertation also presents a review of effective methods for communicating science to various audiences, with specific applications to astronomy. That chapter highlights the necessity of integrating formal communications training into the early stages of a career in astronomy, explains why and how to apply story telling techniques to astronomy communication, and details specific strategies to apply when using common communication media. Examples are given for effectively communicating astronomy through academic research papers, slides for an oral presentation, and academic research posters, as well as examples of popular science blogs, feature articles, and news stories.

Helical comb magnetostrictive patch transducers for inspecting spiral welded pipes using flexural guided waves.

PubMed

Zhang, Xiaowei; Tang, Zhifeng; Lv, Fuzai; Pan, Xiaohong

2017-02-01

A wavefront analysis indicates that a flexural wave propagates at a helix angle with respect to the pipe axis. The expression for calculation of the helix angle for each flexural mode is given, and the helix angle dispersion curves for flexural modes are calculated. According to the new understanding of flexural guided waves, a helical comb magnetostrictive patch transducer (HCMPT) is proposed for selectively exciting a single predominant flexural torsional guided wave in a pipe and inspecting spiral welded pipes using flexural waves. A HCMPT contains a pre-magnetized magnetostrictive patch that is helically coupled with the outer surface of a pipe, and a novel compound comb coil that is wrapped around the helical magnetostrictive patch. The proposed wideband HCMPT possesses the direction control ability. A verification experiment indicates that flexural torsional mode T(3,1) at center frequency f=64kHz is effectively actuated by a HCMPT with 13-degree helix angle. Flexural torsional modes T(N,1) with circumferential order N equals 1-5 are selected to inspect a seamless steel pipe, artificial defects are effectively detected by the proposed HCMPT. A 20-degree HCMPT is adopted to inspect a spiral welded pipe, an artificial notch with cross section loss CSL=2.7% is effectively detected by using flexural waves. Copyright © 2016 Elsevier B.V. All rights reserved.

Logistic regression model can reduce unnecessary artificial liver support in hepatitis B virus-associated acute-on-chronic liver failure: decision curve analysis.

PubMed

Qin, Gang; Bian, Zhao-Lian; Shen, Yi; Zhang, Lei; Zhu, Xiao-Hong; Liu, Yan-Mei; Shao, Jian-Guo

2016-06-04

Several models have been proposed to predict the short-term outcome of acute-on-chronic liver failure (ACLF) after treatment. We aimed to determine whether better decisions for artificial liver support system (ALSS) treatment could be made with a model than without, through decision curve analysis (DCA). The medical profiles of a cohort of 232 patients with hepatitis B virus (HBV)-associated ACLF were retrospectively analyzed to explore the role of plasma prothrombin activity (PTA), model for end-stage liver disease (MELD) and logistic regression model (LRM) in identifying patients who could benefit from ALSS. The accuracy and reliability of PTA, MELD and LRM were evaluated with previously reported cutoffs. DCA was performed to evaluate the clinical role of these models in predicting the treatment outcome. With the cut-off value of 0.2, LRM had sensitivity of 92.6 %, specificity of 42.3 % and an area under the receiving operating characteristic curve (AUC) of 0.68, which showed superior discrimination over PTA and MELD. DCA revealed that the LRM-guided ALSS treatment was superior over other strategies including "treating all" and MELD-guided therapy, for the midrange threshold probabilities of 16 to 64 %. The use of LRM-guided ALSS treatment could increase both the accuracy and efficiency of this procedure, allowing the avoidance of unnecessary ALSS.

Visible Machine Learning for Biomedicine.

PubMed

Yu, Michael K; Ma, Jianzhu; Fisher, Jasmin; Kreisberg, Jason F; Raphael, Benjamin J; Ideker, Trey

2018-06-14

A major ambition of artificial intelligence lies in translating patient data to successful therapies. Machine learning models face particular challenges in biomedicine, however, including handling of extreme data heterogeneity and lack of mechanistic insight into predictions. Here, we argue for "visible" approaches that guide model structure with experimental biology. Copyright © 2018. Published by Elsevier Inc.

United States Air Force History. A Guide to Documentary Sources

DTIC Science & Technology

1973-01-01

artificial limbs, crea- tive activity, and delegates to an interallied congress. The areas represented by aerial photographs are only partially identified...Interim Government of Korea, 154 477, 604 See also Korea, Korean War Hoover, J. Edgar, 604 Seas oeKra aHopkins, HEarr 8, 6 84, 3International Aeroplane Co

Observed Changes in Classroom Behavior Utilizing Supportive Intervention.

ERIC Educational Resources Information Center

Swift, J. Nathan; And Others

The effects of instructional guides and wait-time feedback upon the classroom interaction of 40 middle school science teachers were investigated in a prior study. The experimental nature of that study produced an artificial situation involving little personal contact between teacher-participants and the research staff. Therefore, a subsample of 10…

Role of Educational Games Improves Meaningful Learning

ERIC Educational Resources Information Center

Nachimuthu, K.; Vijayakumari, G.

2011-01-01

A game is a set of activities involving one or more players. It has goals, constraints, payoffs, and consequences. A game is rule-guided and artificial in some respects. (Richard Wilson, 2010). According to Garris et al. (2002), define educational game play as "voluntary, nonproductive, and separate from the real world"; and they found…

Floral Nectar Guide Patterns Discourage Nectar Robbing by Bumble Bees

PubMed Central

Leonard, Anne S.; Brent, Joshua; Papaj, Daniel R.; Dornhaus, Anna

2013-01-01

Floral displays are under selection to both attract pollinators and deter antagonists. Here we show that a common floral trait, a nectar guide pattern, alters the behavior of bees that can act opportunistically as both pollinators and as antagonists. Generally, bees access nectar via the floral limb, transporting pollen through contact with the plant’s reproductive structures; however bees sometimes extract nectar from a hole in the side of the flower that they or other floral visitors create. This behavior is called “nectar robbing” because bees may acquire the nectar without transporting pollen. We asked whether the presence of a symmetric floral nectar guide pattern on artificial flowers affected bumble bees’ (Bombus impatiens) propensity to rob or access nectar “legitimately.” We discovered that nectar guides made legitimate visits more efficient for bees than robbing, and increased the relative frequency of legitimate visits, compared to flowers lacking nectar guides. This study is the first to show that beyond speeding nectar discovery, a nectar guide pattern can influence bees’ flower handling in a way that could benefit the plant. PMID:23418475

Numerical relativity simulations of neutron star merger remnants using conservative mesh refinement

NASA Astrophysics Data System (ADS)

Dietrich, Tim; Bernuzzi, Sebastiano; Ujevic, Maximiliano; Brügmann, Bernd

2015-06-01

We study equal- and unequal-mass neutron star mergers by means of new numerical relativity simulations in which the general relativistic hydrodynamics solver employs an algorithm that guarantees mass conservation across the refinement levels of the computational mesh. We consider eight binary configurations with total mass M =2.7 M⊙, mass ratios q =1 and q =1.16 , four different equations of state (EOSs) and one configuration with a stiff EOS, M =2.5 M⊙ and q =1.5 , which is one of the largest mass ratios simulated in numerical relativity to date. We focus on the postmerger dynamics and study the merger remnant, the dynamical ejecta, and the postmerger gravitational wave spectrum. Although most of the merger remnants are a hypermassive neutron star collapsing to a black hole+disk system on dynamical time scales, stiff EOSs can eventually produce a stable massive neutron star. During the merger process and on very short time scales, about ˜10-3- 10-2M⊙ of material become unbound with kinetic energies ˜1050 erg . Ejecta are mostly emitted around the orbital plane and favored by large mass ratios and softer EOS. The postmerger wave spectrum is mainly characterized by the nonaxisymmetric oscillations of the remnant neutron star. The stiff EOS configuration consisting of a 1.5 M⊙ and a 1.0 M⊙ neutron star, simulated here for the first time, shows a rather peculiar dynamics. During merger the companion star is very deformed; about ˜0.03 M⊙ of the rest mass becomes unbound from the tidal tail due to the torque generated by the two-core inner structure. The merger remnant is a stable neutron star surrounded by a massive accretion disk of rest mass ˜0.3 M⊙. This and similar configurations might be particularly interesting for electromagnetic counterparts. Comparing results obtained with and without the conservative mesh refinement algorithm, we find that postmerger simulations can be affected by systematic errors if mass conservation is not enforced in the mesh refinement strategy. However, mass conservation also depends on grid details and on the artificial atmosphere setup; the latter are particularly significant in the computation of the dynamical ejecta.

Predictive modeling of treatment resistant depression using data from STAR*D and an independent clinical study.

PubMed

Nie, Zhi; Vairavan, Srinivasan; Narayan, Vaibhav A; Ye, Jieping; Li, Qingqin S

2018-01-01

Identification of risk factors of treatment resistance may be useful to guide treatment selection, avoid inefficient trial-and-error, and improve major depressive disorder (MDD) care. We extended the work in predictive modeling of treatment resistant depression (TRD) via partition of the data from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) cohort into a training and a testing dataset. We also included data from a small yet completely independent cohort RIS-INT-93 as an external test dataset. We used features from enrollment and level 1 treatment (up to week 2 response only) of STAR*D to explore the feature space comprehensively and applied machine learning methods to model TRD outcome at level 2. For TRD defined using QIDS-C16 remission criteria, multiple machine learning models were internally cross-validated in the STAR*D training dataset and externally validated in both the STAR*D testing dataset and RIS-INT-93 independent dataset with an area under the receiver operating characteristic curve (AUC) of 0.70-0.78 and 0.72-0.77, respectively. The upper bound for the AUC achievable with the full set of features could be as high as 0.78 in the STAR*D testing dataset. Model developed using top 30 features identified using feature selection technique (k-means clustering followed by χ2 test) achieved an AUC of 0.77 in the STAR*D testing dataset. In addition, the model developed using overlapping features between STAR*D and RIS-INT-93, achieved an AUC of > 0.70 in both the STAR*D testing and RIS-INT-93 datasets. Among all the features explored in STAR*D and RIS-INT-93 datasets, the most important feature was early or initial treatment response or symptom severity at week 2. These results indicate that prediction of TRD prior to undergoing a second round of antidepressant treatment could be feasible even in the absence of biomarker data.

New numerical determination of habitability in the Galaxy: the SETI connection

NASA Astrophysics Data System (ADS)

Ramirez, Rodrigo; Gómez-Muñoz, Marco A.; Vázquez, Roberto; Núñez, Patricia G.

2018-01-01

In this paper, we determine the habitability of Sun-like stars in the Galaxy using Monte Carlo simulations, which are guided by the factors of the Drake Equation for the considerations on the astrophysical and biological parameters needed to generate and maintain life on a planet's surface. We used a simple star distribution, initial mass function and star formation history to reproduce the properties and distribution of stars within the Galaxy. Using updated exoplanet data from the Kepler mission, we assign planets to some of the stars, and then follow the evolution of life on the planets that met the habitability criteria using two different civilization hypotheses. We predict that around 51% of Earth-like planets in the habitable zone (HZ) are inhabited by primitive life and 4% by technological life. We apply the results to the Kepler field of view, and predicted that there should be at least six Earth-like planets in the HZ, three of them inhabited by primitive life. According to our model, non-technological life is very common if there are the right conditions, but communicative civilizations are less likely to exist and detect. Nonetheless, we predict a considerable number of detectable civilizations within our Galaxy, making it worthwhile to keep searching.

Status and new developments with the Keck I near-infrared tip-tilt sensor

NASA Astrophysics Data System (ADS)

Femenía Castellá, Bruno; Wizinowich, Peter; Rampy, Rachel; Cetre, Sylvain; Lilley, Scott; Lyke, Jim; Ragland, Sam; Stomski, Paul; van Dam, Marcos

2016-07-01

The sky coverage and performance of Laser Guide Star (LGS) adaptive optics (AO) systems is limited by the Natural Guide Star (NGS) used for low order correction (tip-tilt and defocus modes). This limitation can be reduced by measuring image motion of the NGS in the near-infrared where it is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We have integrated a Near-InfraRed Tip-Tilt Sensor (NIRTTS) with the Keck I telescopes LGS AO system. The sensor is a H2RG-based near-infrared camera with 0.05 arcsecond pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2x2 to 16x16 pixels, centered on an NGS anywhere in an 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beam-splitters located in front of the OSIRIS integral field spectrograph. The implementation of the NIRTTS involved modifications to the AO bench, real-time control system, higher-level controls and operations software. NIRTTS is nearly ready for science operation in shared-risk mode. We are also implementing a number of enhancements to the NIRTTS system which involve substantial changes to the operations software. This work presents an update of the work performed since the NIRTTS system was reported in Ref. 1 and Ref. 2.

The “UV-route” to Search for Blue Straggler Stars in Globular Clusters: First Results from the HST UV Legacy Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raso, S.; Ferraro, F. R.; Lanzoni, B.

We used data from the Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters to select the Blue Straggler Star (BSS) population in four intermediate/high density systems (namely NGC 2808, NGC 6388, NGC 6541, and NGC 7078) through a “UV-guided search.” This procedure consists of using the F275W images in each cluster to construct the master list of detected sources, and then force it to the images acquired in the other filters. Such an approach optimizes the detection of relatively hot stars and allows the detection of a complete sample of BSSs even in the central region of high-densitymore » clusters, because the light from the bright cool giants, which dominates the optical emission in old stellar systems, is sensibly reduced at UV wavelengths. Our UV-guided selections of BSSs have been compared to the samples obtained in previous, optical-driven surveys, clearly demonstrating the efficiency of the UV approach. In each cluster we also measured the parameter A {sup +}, defined as the area enclosed between the cumulative radial distribution of BSSs and that of a reference population, which traces the level of BSS central segregation and the level of dynamical evolution suffered by the system. The values measured for the four clusters studied in this paper nicely fall along the dynamical sequence recently presented for a sample of 25 clusters.« less

CosmoQuest: Virtual Star Parties as a Conduit to Citizen Science Research

NASA Astrophysics Data System (ADS)

Lewis, Scott; Gugliucci, N. E.; Gay, P. L.; Amateur Astronomer Team; Commentator Team

2013-01-01

CosmoQuest has created an environment that actively engages the public through online star parties while building a growing virtual research center that allows individuals anywhere in the world to participate in and contribute to scientific research. Utilizing the infrastructure of Google+ and YouTube, CosmoQuest has brought optical observational astronomy into homes across the world. Every week astronomers - amateur and professional - meet to share live sky images and to discuss the science behind their beauty during Virtual Star parties. A wide array of optics and digital detectors from varied locations collaborate in a fashion not possible in the standard public star party. Every viewer is able to virtually look through the imaging telescope simultaneously while the equipment owner doesn’t need to worry about accidental mishandling by the public. Digital cameras and CCDs also allow longer exposures of deep-sky objects, something not typical in a standard star party event. Our diversity of equipment - ranging from hand-guided Dobsonian telescopes to 16” Schmidt-Cassegrain telescopes on Paramounts - give viewers the opportunity to experience the sky through different systems. Additional Star Parties focus on special astronomical events, such as eclipses and transits. The annular eclipse of 20 May, 2012 brought together astronomers, space enthusiasts and a curious public into a Google+ Hangout On Air to celebrate the event while advocating safe observing methods and explaining the science behind the phenomenon. Public photos of the eclipse were shared live in the broadcast while video of the event was streamed for thousands of viewers to enjoy. Other special event star parties have focused on the Super Moon, Eros Opposition, and the Venus Transit. In this poster we review the technology behind star parties and the reach of these events.

ATLASGAL: Chemical evolution of star forming clumps

NASA Astrophysics Data System (ADS)

Figura, Charles C.; Urquhart, James S.; Wyrowski, Friedrich

2017-01-01

Although massive stars are few in number, they impact their host molecular clouds, clusters, and galaxies in profound ways, playing a vital role in regulating star formation in their host galaxy. Understanding the formation of these massive stars is critical to understanding this evolution, but their rapid early development causes them to reach the main sequence while still shrouded in their natal molecular cloud. Many studies have investigated these regions in a targeted manner, but a full understanding necessitates a broader view at all stages of formation across many star forming regions.We have used mid-infrared continuum surveys to guide selection of a statistically large sample of massive dust clumps from the 10,000 such clumps identified in the ATLASGAL Compact Source Catalogue (CSC), ensuring that all stages of the evolutionary process are included. A final sample of 600 fourth-quadrant sources within 1 degree of the Galactic plane were observed with the Mopra telescope with an 8 GHz bandwidth between 85.2 and 93.4 GHz.We present an overview of our results. We have identified over 30 molecular lines, seven of which with detected hyperfine structure, as well as several mm-radio recombination line transitions. Source velocities indicate that these regions trace the Crux-Scutum, Norma, and Carina Sagitarius arms. We have performed an analysis of linewidth and line intensity ratios, correlating these with star formation stages as identified by IR brightness at the 70 and 24 μm bands, and present several molecular pairs whose linewidth and intensity might serve as significant tracers of the evolutionary stage of star formation. We comment on the results of PCA analysis of the measured parameters for the overall population and the star formation stage subgroups with an eye toward characterising early stellar development through molecular line observations.

Swallowing Mechanics Associated With Artificial Airways, Bolus Properties, and Penetration-Aspiration Status in Trauma Patients.

PubMed

Dietsch, Angela M; Rowley, Christopher B; Solomon, Nancy Pearl; Pearson, William G

2017-09-18

Artificial airway procedures such as intubation and tracheotomy are common in the treatment of traumatic injuries, and bolus modifications may be implemented to help manage swallowing disorders. This study assessed artificial airway status, bolus properties (volume and viscosity), and the occurrence of laryngeal penetration and/or aspiration in relation to mechanical features of swallowing. Coordinates of anatomical landmarks were extracted at minimum and maximum hyolaryngeal excursion from 228 videofluoroscopic swallowing studies representing 69 traumatically injured U.S. military service members with dysphagia. Morphometric canonical variate and regression analyses examined associations between swallowing mechanics and bolus properties based on artificial airway and penetration-aspiration status. Significant differences in swallowing mechanics were detected between extubated versus tracheotomized (D = 1.32, p < .0001), extubated versus decannulated (D = 1.74, p < .0001), and decannulated versus tracheotomized (D = 1.24, p < .0001) groups per post hoc discriminant function analysis. Tracheotomy-in-situ and decannulated subgroups exhibited increased head/neck extension and posterior relocation of the larynx. Swallowing mechanics associated with (a) penetration-aspiration status and (b) bolus properties were moderately related for extubated and decannulated subgroups, but not the tracheotomized subgroup, per morphometric regression analysis. Specific differences in swallowing mechanics associated with artificial airway status and certain bolus properties may guide therapeutic intervention in trauma-based dysphagia.

The Role of Artificial Intelligence in Diagnostic Radiology: A Survey at a Single Radiology Residency Training Program.

PubMed

Collado-Mesa, Fernando; Alvarez, Edilberto; Arheart, Kris

2018-02-21

Advances in artificial intelligence applied to diagnostic radiology are predicted to have a major impact on this medical specialty. With the goal of establishing a baseline upon which to build educational activities on this topic, a survey was conducted among trainees and attending radiologists at a single residency program. An anonymous questionnaire was distributed. Comparisons of categorical data between groups (trainees and attending radiologists) were made using Pearson χ 2 analysis or an exact analysis when required. Comparisons were made using the Wilcoxon rank sum test when the data were not normally distributed. An α level of 0.05 was used. The overall response rate was 66% (69 of 104). Thirty-six percent of participants (n = 25) reported not having read a scientific medical article on the topic of artificial intelligence during the past 12 months. Twenty-nine percent of respondents (n = 12) reported using artificial intelligence tools during their daily work. Trainees were more likely to express doubts on whether they would have pursued diagnostic radiology as a career had they known of the potential impact artificial intelligence is predicted to have on the specialty (P = .0254) and were also more likely to plan to learn about the topic (P = .0401). Radiologists lack exposure to current scientific medical articles on artificial intelligence. Trainees are concerned by the implications artificial intelligence may have on their jobs and desire to learn about the topic. There is a need to develop educational resources to help radiologists assume an active role in guiding and facilitating the development and implementation of artificial intelligence tools in diagnostic radiology. Copyright © 2017 American College of Radiology. Published by Elsevier Inc. All rights reserved.

Investigation of return photons from sodium laser beacon excited by a 40-watt facility-class pulsed laser for adaptive optical telescope applications.

PubMed

Bian, Qi; Bo, Yong; Zuo, Junwei; Li, Min; Dong, Ruoxi; Deng, Keran; Zhang, Dingwen; He, Liping; Zong, Qingshuang; Cui, Dafu; Peng, Qinjun; Chen, Hongbin; Xu, Zuyan

2018-06-15

The brightness of the artificial beacon is one critical performance parameter for adaptive optics. Here, a 40-watt level narrow-linewidth microsecond pulsed yellow laser is produced at 589 nm with a high repetition frequency of 600 Hz and a pulse duration of 120 μs. An experiment to project the pulse beam up to the sky and measure the fluorescence photon returns of the Na atoms has been held on the 1.8-meter telescope in Lijiang observatory. During the sky test, a laser guide star (LGS) spot is firstly observed with Rayleigh scattering elimination by means of a gateable pulse format. And, the central wavelength of the laser could be accurately locked to be 589.1584 nm with a linewidth of ~0.34 GHz to match that of sodium-D 2a line. Optical pumping with circularly polarized light has also been used to increase the brightness of sodium LGS. In order to maximize the return flux, sodium D 2b repumping option is done by an electro-optic modulator with the optimum D 2a -D 2b frequency offset. As a result, a bright sodium LGS with the return flux of 1610 photons/cm 2 /s is achieved, corresponding to ~47 photons/cm 2 /s/W of emitted laser power, which represents a significant improvement in terms of brightness reported ever.

Photometric detection of a candidate low-mass giant binary system at the Milky Way Galactic Center

NASA Astrophysics Data System (ADS)

Krishna Gautam, Abhimat; Do, Tuan; Ghez, Andrea; Sakai, Shoko; Morris, Mark; Lu, Jessica; Witzel, Gunther; Jia, Siyao; Becklin, Eric Eric; Matthews, Keith

2018-01-01

We present the discovery of a new periodic variable star at the Milky Way Galactic Center (GC). This study uses laser guide-star adaptive optics data collected with the W. M. Keck 10 m telescope in the K‧-band (2.2 µm) over 35 nights spanning an 11 year time baseline, and 5 nights of additional H-band (1.6 µm) data. We implemented an iterative photometric calibration and local correction technique, resulting in a photometric uncertainty of Δm_K‧ ∼ 0.03 to a magnitude of m_K‧ ∼ 16.The periodically variable star has a 39.42 day period. We find that the star is not consistent with known periodically variable star classes in this period range with its observed color and luminosity, nor with an eclipsing binary system. The star's color and luminosity are however consistent with an ellipsoidal binary system at the GC, consisting of a K-giant and a dwarf component with an orbital period of 78.84 days. If a binary system, it represents the first detection of a low-mass giant binary system in the central half parsec of the GC. Such long-period binary systems can easily evaporate in the dense environment of the GC due to interactions with other stars. The existence and properties of a low-mass, long-period binary system can thus place valuable constraints on dynamical models of the GC environment and probe the density of the hypothesized dark cusp of stellar remnants at the GC.

KSC-2011-1910

NASA Image and Video Library

2011-02-28

CAPE CANAVERAL, Fla. -- The left spent booster used during space shuttle Discovery's final launch is guided into a hoisting slip at the Solid Rocket Booster Disassembly Facility at Hangar AF on Cape Canaveral Air Force Station in Florida. The shuttle's two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be refurbished and stored, if needed. Photo credit: NASA/Jim Grossmann

KSC-2011-1912

NASA Image and Video Library

2011-02-28

CAPE CANAVERAL, Fla. -- The left spent booster used during space shuttle Discovery's final launch is guided into a hoisting slip at the Solid Rocket Booster Disassembly Facility at Hangar AF on Cape Canaveral Air Force Station in Florida. The shuttle's two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be refurbished and stored, if needed. Photo credit: NASA/Jim Grossmann

KSC-2011-1913

NASA Image and Video Library

2011-02-28

CAPE CANAVERAL, Fla. -- Workers in a small raft, guide the left spent booster used during space shuttle Discovery's final launch into position in a hoisting slip at the Solid Rocket Booster Disassembly Facility at Hangar AF on Cape Canaveral Air Force Station in Florida. The shuttle's two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be refurbished and stored, if needed. Photo credit: NASA/Jim Grossmann

Exploration of peptides that fit into the thermally vibrating active site of cathepsin K protease by alternating artificial intelligence and molecular simulation

NASA Astrophysics Data System (ADS)

Nishiyama, Katsuhiko

2017-08-01

Eighteen tripeptides that fit into the thermally vibrating active site of cathepsin K were discovered by alternating artificial intelligence and molecular simulation. The 18 tripeptides fit the active site better than the cysteine protease inhibitor E64, and a better inhibitor of cathepsin K could be designed considering these tripeptides. Among the 18 tripeptides, Phe-Arg-Asp and Tyr-Arg-Asp fit the active site the best and their structural similarity should be considered in the design process. Interesting factors emerged from the structure of the decision tree, and its structural information will guide exploration of potential inhibitor molecules for proteases.

CI Controls for Energy and Environment

NASA Technical Reports Server (NTRS)

Biondo, Samuel J.

1996-01-01

Computational intelligence (CI) is a rapidly evolving field that utilizes life imitating metaphors for guiding model building including, but not limited to neural networks, fuzzy logic, genetic algorithms, artificial life, and hybrid CI paradigms. Although the boundaries between artificial intelligence (AI) and CI are not distinct, their research communities are separate and distinct. CI researchers tend to focus on processing numerical data from sensors, while the AI community generally relies on symbolic computing to capture human knowledge. In both areas, there is a great deal of interest and activity in hybrid systems that can offset the limitations of individual methods, extend their capabilities, and create new capabilities. Examples of the benefits that can accrue from hybrid systems are contained.

Artificial bee colony algorithm with dynamic multi-population

NASA Astrophysics Data System (ADS)

Zhang, Ming; Ji, Zhicheng; Wang, Yan

2017-07-01

To improve the convergence rate and make a balance between the global search and local turning abilities, this paper proposes a decentralized form of artificial bee colony (ABC) algorithm with dynamic multi-populations by means of fuzzy C-means (FCM) clustering. Each subpopulation periodically enlarges with the same size during the search process, and the overlapping individuals among different subareas work for delivering information acting as exploring the search space with diffusion of solutions. Moreover, a Gaussian-based search equation with redefined local attractor is proposed to further accelerate the diffusion of the best solution and guide the search towards potential areas. Experimental results on a set of benchmarks demonstrate the competitive performance of our proposed approach.

Robotics and artificial intelligence: Jewish ethical perspectives.

PubMed

Rappaport, Z H

2006-01-01

In 16th Century Prague, Rabbi Loew created a Golem, a humanoid made of clay, to protect his community. When the Golem became too dangerous to his surroundings, he was dismantled. This Jewish theme illustrates some of the guiding principles in its approach to the moral dilemmas inherent in future technologies, such as artificial intelligence and robotics. Man is viewed as having received the power to improve upon creation and develop technologies to achieve them, with the proviso that appropriate safeguards are taken. Ethically, not-harming is viewed as taking precedence over promoting good. Jewish ethical thinking approaches these novel technological possibilities with a cautious optimism that mankind will derive their benefits without coming to harm.

Photon collider: a four-channel autoguider solution

NASA Astrophysics Data System (ADS)

Hygelund, John C.; Haynes, Rachel; Burleson, Ben; Fulton, Benjamin J.

2010-07-01

The "Photon Collider" uses a compact array of four off axis autoguider cameras positioned with independent filtering and focus. The photon collider is two way symmetric and robustly mounted with the off axis light crossing the science field which allows the compact single frame construction to have extremely small relative deflections between guide and science CCDs. The photon collider provides four independent guiding signals with a total of 15 square arc minutes of sky coverage. These signals allow for simultaneous altitude, azimuth, field rotation and focus guiding. Guide cameras read out without exposure overhead increasing the tracking cadence. The independent focus allows the photon collider to maintain in focus guide stars when the main science camera is taking defocused exposures as well as track for telescope focus changes. Independent filters allow auto guiding in the science camera wavelength bandpass. The four cameras are controlled with a custom web services interface from a single Linux based industrial PC, and the autoguider mechanism and telemetry is built around a uCLinux based Analog Devices BlackFin embedded microprocessor. Off axis light is corrected with a custom meniscus correcting lens. Guide CCDs are cooled with ethylene glycol with an advanced leak detection system. The photon collider was built for use on Las Cumbres Observatory's 2 meter Faulks telescopes and currently used to guide the alt-az mount.

On the origin of jets from disc-accreting magnetized stars

NASA Astrophysics Data System (ADS)

Lovelace, Richard V. E.; Romanova, Marina M.; Lii, Patrick; Dyda, Sergei

2014-09-01

A brief review of the origin of jets from disc-accreting rotating magnetized stars is given. In most models, the interior of the disc is characterized by a turbulent viscosity and magnetic diffusivity ("alpha" discs) whereas the coronal region outside the disc is treated using ideal magnetohydrodynamics (MHD). Extensive MHD simulations have established the occurrence of long-lasting outflows in the case of both slowly and rapidly rotating stars. (1) Slowly rotating stars exhibit a new type of outflow, conical winds. Conical winds are generated when stellar magnetic flux is bunched up by the inward motion of the accretion disc. Near their region of origin, the winds have a thin conical shell shape with half opening angle of ˜30°. At large distances, their toroidal magnetic field collimates the outflow forming current carrying, matter dominated jets. These winds are predominantly magnetically and not centrifugally driven. About 10-30% of the disc matter from the inner disc is launched in the conical wind. Conical winds may be responsible for episodic as well as long lasting outflows in different types of stars. (2) Rapidly rotating stars in the "propeller regime" exhibit two-component outflows. One component is similar to the matter dominated conical wind, where a large fraction of the disc matter may be ejected in this regime. The second component is a high-velocity, low-density magnetically dominated axial jet where matter flows along the open polar field lines of the star. The axial jet has a mass flux of about 10% that of the conical wind, but its energy flux, due to the Poynting flux, can be as large as for the conical wind. The jet's magnetically dominated angular momentum flux causes the star to spin down rapidly. Propeller-driven outflows may be responsible for protostellar jets and their rapid spin-down. When the artificial requirement of symmetry about the equatorial plane is dropped, the conical winds are found to come alternately from one side of the disc and then the other, even for the case where the stellar magnetic field is a centered axisymmetric dipole. Recent MHD simulations of disc accretion to rotating stars in the propeller regime have been done with no turbulent viscosity and no diffusivity. The strong turbulence observed is due to the magneto-rotational instability. This turbulence drives accretion in the disc and leads to episodic conical winds and jets.

Guided by a Red Star: The Cuban Literacy Campaign and the Challenge of History

ERIC Educational Resources Information Center

McLaren, Peter

2009-01-01

This article features the book "Rebel Literacy: Cuba's National Literacy Campaign and Critical Global Citizenship," by Mark Abendroth, a step-child of the Critical Pedagogy Program at the University of Saint Thomas. As a scholar-activist, Abendroth has produced a courageous and prescient volume that will impact the field of critical…

Ancient Earth, Alien Earths Event

NASA Image and Video Library

2014-08-20

Panelists pose for a group photo at the “Ancient Earth, Alien Earths” Event at NASA Headquarters in Washington, DC Wednesday, August 20, 2014. The event was sponsored by NASA, the National Science Foundation (NSF), and the Smithsonian Institution and highlighted how research on early Earth could help guide our search for habitable planets orbiting other stars. Photo Credit: (NASA/Aubrey Gemignani)

ENERGY STAR® Retail Products Platform (RPP): Conditions and Considerations in Evaluating Market Transformation Programs and Evaluation Guidance for RPP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Michael; Banwell, Peter

2018-01-09

The purpose of this guide is to provide a resource for state utility regulators, utilities, the evaluation community and regulatory stakeholders on methods to measure energy savings from the ENERGY STAR Retail Products Platform (link is external). The guidelines outlined in this document were developed by evaluation experts.

At Saturn: Tripping the Flight Fantastic

NASA Astrophysics Data System (ADS)

Porco, Carolyn C.

2008-05-01

Boulder planetary scientist Carolyn Porco, leader of the imaging team for NASA's Cassini mission to Saturn and science advisor for the forthcoming movie "Star Trek," guides you on a magical mystery tour around the ringed planet. Come and witness the wonders, discoveries, and the awesome natural beauty of this amazing planet and its family of rings and moons.

The Office of Diversity and Inclusion at a Large Texas University: A Cultural Evolution

ERIC Educational Resources Information Center

Curette, Alvin R.

2016-01-01

This single, holistic, instrumental case study investigated the organizational history of the Office of Diversity and Inclusion (ODI) at Lone Star University. The study included an examination of changes to ODI's cultural identity. This study was guided by two principal research questions: a) Why was the office created and how has its cultural…

Some first experiments on the photometric calibration of Schmidt plates against the Tycho catalogue

NASA Technical Reports Server (NTRS)

Morrison, J. E.; Lasker, B.; McLean, B.; Bucciarelli, B.; Spagna, A.; Zacchei, A.

1997-01-01

Preliminary work carried out with the aim of reducing the Guide Star Catalog (GSC2) measurements of the Palomar 2 plates with the Tycho catalog for a 625 sq deg test field centered on the North Galactic Pole, is reported on and the results are presented. The emphasis was on the photometric calibrations.

The Young Astrophysicist: A Very Inexpensive Activity to Discuss Spectroscopy

ERIC Educational Resources Information Center

Brockington, Guilherme; Testoni, Leonardo André; Pietrocola, Maurício

2015-01-01

The continuing fascination of young people with celestial bodies leads them to pose challenging questions to their science teachers, such as how was the universe born? How were the stars formed? In this paper we present an extremely inexpensive but highly engaging activity to teach the basics of spectroscopy. Guided by the question "how do…

Vegetation in transition: the Southwest's dynamic past century

Treesearch

Raymond M. Turner

2005-01-01

Monitoring that follows long-term vegetation changes often requires selection of a temporal baseline. Any such starting point is to some degree artificial, but in some instances there are aids that can be used as guides to baseline selection. Matched photographs duplicating scenes first recorded on film a century or more ago reveal changes that help select the starting...

HUBBLE TARANTULA TREASURY PROJECT. III. PHOTOMETRIC CATALOG AND RESULTING CONSTRAINTS ON THE PROGRESSION OF STAR FORMATION IN THE 30 DORADUS REGION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabbi, E.; Anderson, J.; Cignoni, M.

2016-01-15

We present and describe the astro-photometric catalog of more than 800,000 sources found in the Hubble Tarantula Treasury Project (HTTP). HTTP is a Hubble Space Telescope Treasury program designed to image the entire 30 Doradus region down to the sub-solar (∼0.5 M{sub ⊙}) mass regime using the Wide Field Camera 3 and the Advanced Camera for Surveys. We observed 30 Doradus in the near-ultraviolet (F275W, F336W), optical (F555W, F658N, F775W), and near-infrared (F110W, F160W) wavelengths. The stellar photometry was measured using point-spread function fitting across all bands simultaneously. The relative astrometric accuracy of the catalog is 0.4 mas. The astro-photometric catalog,more » results from artificial star experiments, and the mosaics for all the filters are available for download. Color–magnitude diagrams are presented showing the spatial distributions and ages of stars within 30 Dor as well as in the surrounding fields. HTTP provides the first rich and statistically significant sample of intermediate- and low-mass pre-main sequence candidates and allows us to trace how star formation has been developing through the region. The depth and high spatial resolution of our analysis highlight the dual role of stellar feedback in quenching and triggering star formation on the giant H ii region scale. Our results are consistent with stellar sub-clustering in a partially filled gaseous nebula that is offset toward our side of the Large Magellanic Cloud.« less

Detecting unresolved binary stars in Euclid VIS images

NASA Astrophysics Data System (ADS)

Kuntzer, T.; Courbin, F.

2017-10-01

Measuring a weak gravitational lensing signal to the level required by the next generation of space-based surveys demands exquisite reconstruction of the point-spread function (PSF). However, unresolved binary stars can significantly distort the PSF shape. In an effort to mitigate this bias, we aim at detecting unresolved binaries in realistic Euclid stellar populations. We tested methods in numerical experiments where (I) the PSF shape is known to Euclid requirements across the field of view; and (II) the PSF shape is unknown. We drew simulated catalogues of PSF shapes for this proof-of-concept paper. Following the Euclid survey plan, the objects were observed four times. We propose three methods to detect unresolved binary stars. The detection is based on the systematic and correlated biases between exposures of the same object. One method is a simple correlation analysis, while the two others use supervised machine-learning algorithms (random forest and artificial neural network). In both experiments, we demonstrate the ability of our methods to detect unresolved binary stars in simulated catalogues. The performance depends on the level of prior knowledge of the PSF shape and the shape measurement errors. Good detection performances are observed in both experiments. Full complexity, in terms of the images and the survey design, is not included, but key aspects of a more mature pipeline are discussed. Finding unresolved binaries in objects used for PSF reconstruction increases the quality of the PSF determination at arbitrary positions. We show, using different approaches, that we are able to detect at least binary stars that are most damaging for the PSF reconstruction process. The code corresponding to the algorithms used in this work and all scripts to reproduce the results are publicly available from a GitHub repository accessible via http://lastro.epfl.ch/software

The First US Naval Observatory CCD Astrograph Catalog

NASA Astrophysics Data System (ADS)

Zacharias, N.; Urban, S. E.; Zacharias, M. I.; Hall, D. M.; Wycoff, G. L.; Rafferty, T. J.; Germain, M. E.; Holdenried, E. R.; Pohlman, J. W.; Gauss, F. S.; Monet, D. G.; Winter, L.

2000-10-01

The USNO CCD Astrograph (UCA) started an astrometric survey in 1998 February at Cerro Tololo, Chile. This first, preliminary catalog (UCAC1) includes data taken up to 1999 November with about 80% of the Southern Hemisphere covered. Observing continues, and full sky coverage is expected by mid-2003 after moving the instrument to a Northern Hemisphere site in early 2001. The survey is performed in a single bandpass (579-642 nm), a twofold overlap pattern of fields, and with a long and a short exposure on each field. Stars in the magnitude range 10-14 have positional precisions of <=20 mas. At the limiting magnitude of R~16 mag, the positional precision is 70 mas. The UCAC aims at a density (stars per square degree) larger than that of the Guide Star Catalog (GSC) with a positional accuracy similar to Tycho. The UCAC program is a major step toward a high-precision densification of the optical reference frame in the post-Hipparcos era, and the first stage, the UCAC1 contains over 27 million stars. Preliminary proper motions are included, which were derived from Tycho-2, Hipparcos, and ground-based transit circle and photographic surveys for the bright stars (V<=12.5 mag) and the USNO A2.0 for the fainter stars. The accuracy of the proper motions varies widely, from 1 to over 15 mas yr-1. The UCAC1 is available on CD-ROM from the US Naval Observatory.

No Evidence of Chemical Abundance Variations in the Intermediate-age Cluster NGC 1783

NASA Astrophysics Data System (ADS)

Zhang, Hao; de Grijs, Richard; Li, Chengyuan; Wu, Xiaohan

2018-02-01

We have analyzed multi-passband photometric observations, obtained with the Hubble Space Telescope, of the massive (1.8 × 105 M ⊙), intermediate-age (1.8 Gyr-old) Large Magellanic Cloud star cluster NGC 1783. The morphology of the cluster’s red giant branch does not exhibit a clear broadening beyond its intrinsic width; the observed width is consistent with that owing to photometric uncertainties alone and independent of the photometric selection boundaries we applied to obtain our sample of red giant stars. The color dispersion of the cluster’s red giant stars around the best-fitting ridgeline is 0.062 ± 0.009 mag, which is equivalent to the width of 0.080 ± 0.001 mag derived from artificial simple stellar population tests, that is, tests based on single-age, single-metallicity stellar populations. NGC 1783 is comparably as massive as other star clusters that show clear evidence of multiple stellar populations. After incorporating mass-loss recipes from its current age of 1.8 Gyr to an age of 6 Gyr, NGC 1783 is expected to remain as massive as some other clusters that host clear multiple populations at these intermediate ages. If we were to assume that mass is an important driver of multiple population formation, then NGC 1783 should have exhibited clear evidence of chemical abundance variations. However, our results support the absence of any chemical abundance variations in NGC 1783.

THE GHOSTS SURVEY. I. HUBBLE SPACE TELESCOPE ADVANCED CAMERA FOR SURVEYS DATA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radburn-Smith, D. J.; Dalcanton, J. J.; De Jong, R. S.

2011-08-01

We present an overview of the GHOSTS survey, the largest study to date of the resolved stellar populations in the outskirts of disk galaxies. The sample consists of 14 disk galaxies within 17 Mpc, whose outer disks and halos are imaged with the Hubble Space Telescope Advanced Camera for Surveys (ACS). In the first paper of this series, we describe the sample, explore the benefits of using resolved stellar populations, and discuss our ACS F606W and F814W photometry. We use artificial star tests to assess completeness and use overlapping regions to estimate photometric uncertainties. The median depth of the surveymore » at 50% completeness is 2.7 mag below the tip of the red giant branch (TRGB). We comprehensively explore and parameterize contamination from unresolved background galaxies and foreground stars using archival fields of high-redshift ACS observations. Left uncorrected, these would account for 10{sup 0.65xF814W-19.0} detections per mag per arcsec{sup 2}. We therefore identify several selection criteria that typically remove 95% of the contaminants. Even with these culls, background galaxies are a significant limitation to the surface brightness detection limit which, for this survey, is typically V {approx} 30 mag arcsec{sup -2}. The resulting photometric catalogs are publicly available and contain some 3.1 million stars across 76 ACS fields, predominantly of low extinction. The uniform magnitudes of TRGB stars in these fields enable galaxy distance estimates with 2%-7% accuracy.« less

One-Meter Telescope in Kolonica Saddle - 4 Years of Operation

NASA Astrophysics Data System (ADS)

Kudzej, I.; Dubovsky, P. A.

2010-12-01

The actual technical status of 1 meter Vihorlat National Telescope (VNT) at Astronomical Observatory at Kolonica Saddle is presented. Cassegrain and Nasmyth focus, autoguiding system, computer controlled focusing and fine movements and other improvements achieved recently. For two channel photoelectric photometer the system of channels calibration based on artificial light source is described. For CCD camera FLI PL1001E actually installed in Cassegrain focus we presents transformation coefficients from our instrumental to international photometric BVRI system. The measurements were done during regular observations when good photometry of the constant field stars was available. Before FLI camera acquisition we used SBIG ST9 camera. Transformation coefficients for this instrument are presented as well. In the second part of the paper we presents results of variable stars observations with 1 meter telescope in recent four years. The first experimental electronic measurements were done in 2006. Both with CCD cameras and with two channel photoelectric photometer. Starting in 2007 the regular observing program is in operation. There are only few stars suitable for two channel photoelectric photometer observation. Generally the photometer is better when fast brightness changes (time scale of seconds) must be recorded. Thus the majority of observations is done with CCD detectors. We presents an brief overview of most important observing programs: long term monitoring of selected intermediate polars, eclipse observations of SW Sex stars. Occasional observing campaigns were performed on several interesting objects: OT J071126.0+440405, V603 Aql, V471 Tau eclipse timings, Z And in outburst.

Reduction of herbivorous fish pressure can facilitate focal algal species forestation on artificial structures.

PubMed

Gianni, Fabrizio; Bartolini, Fabrizio; Airoldi, Laura; Mangialajo, Luisa

2018-07-01

Coastal areas have been transformed worldwide by urbanization, so that artificial structures are now widespread. Current coastal development locally depletes many native marine species, while offering limited possibilities for their expansion. Eco-engineering interventions intend to identify ways to facilitate the presence of focal species and their associated functions on artificial habitats. An important but overlooked factor controlling restoration operations is overgrazing by herbivores. The aim of this study was to quantify the effects of different potential feeders on Cystoseira amentacea, a native canopy-forming alga of the Mediterranean infralittoral fringe, and test whether manipulation of grazing pressure can facilitate the human-guided installation of this focal species on coastal structures. Results of laboratory tests and field experiments revealed that Sarpa salpa, the only strictly native herbivorous fish in the Western Mediterranean Sea, can be a very effective grazer of C. amentacea in artificial habitats, up to as far as the infralittoral fringe, which is generally considered less accessible to fishes. S. salpa can limit the success of forestation operations in artificial novel habitats, causing up to 90% of Cystoseira loss after a few days. Other grazers, such as limpets and crabs, had only a moderate impact. Future engineering operations,intended to perform forestation of canopy-forming algae on artificial structures, should consider relevant biotic factors, such as fish overgrazing, identifying cost-effective techniques to limit their impact, as is the usual practice in restoration programmes on land. Copyright © 2018 Elsevier Ltd. All rights reserved.

Calin Popovici (1910-1977): The Founder of Modern Astrophysics in Romania

NASA Astrophysics Data System (ADS)

Dumitrescu, A.; Maris, G.

2007-03-01

Connected to the development of astrophysics at the world level, animated by the wish to create a Romanian school of astrophysics and getting understanding and support from the director of the Observatory, the academician Gheorghe Demetrescu, Prof. Calin Popovici laid the basis of the new sector of solar researches, whose coordinator he became in 1955. After the launch of the first artificial satellite on 4 October 1957, Prof. C. Popovici, anticipating the importance of space research in the future, organized at Bucharest Observatory one of the first artificial satellites tracking station in Europe. Later, the group of artificial satellites was set up, whose research focused especially on two new research fields: cosmic triangulation and the study of high atmosphere by means of artificial satellites. It was also at the initiative of Prof. Popovici that in 1962 the second pavilion (after the solar one) was built and was endowed with the new Cassegrain telescope (50/750 cm) equipped with a high precision photoelectric photometer. Thus, the new research sector dedicated to variable stars study was set up. Due to his high professionalism, abnegation and passion for astronomy, Prof. C. Popovici managed to overcome some political difficulties, and his dream of creating a section of astrophysics had come true. Prof. C. Popovici had also an exceptional merit in the scientific training of his collaborators. His vast activity carried out throughout the years in the service of astronomy, education and culture was rewarded with the distinction of academician granted post-mortem.

NEAT: a spatial telescope to detect nearby exoplanets using astrometry

NASA Astrophysics Data System (ADS)

Crouzier, Antoine

2015-01-01

With the present state of exoplanet detection techniques, none of the rocky planets of the Solar System would be discovered, yet their presence is a very strong constraint on the scenarios of formation of planetary systems. Astrometry, by measuring the reflex effect of planets on their central host stars, lead us to the mass of planets and to their orbit determination. This technique is used frequently and is very successful to determine the masses and the orbits of binary stars. From space, it is possible to use differential astrometry around nearby Solar-type stars to detect exoplanets down to one Earth mass in habitable zone, where the sensitivity of the technique is optimal. Finding habitable Earths in the Solar neighborhood would be a major step forward for exoplanet detection and these planets would be prime targets for attempting to find life outside of the Solar System, by searching for bio-markers in their atmospheres. A scientific consortium has formed to promote this kind of astrometric space mission. A mission called NEAT (Nearby Earth Astrometric Telescope) has been proposed to ESA in 2010. A laboratory testbed called NEAT-demo was assembled at IPAG, its main goal is to demonstrate CCD detector calibration to the required accuracy. During my PhD, my activities were related to astrophysical aspects as well as instrumental aspects of the mission. Regarding the scientific case, I compiled a catalog of mission target stars and reference stars (needed for the differential astrometric measurements) and I estimated the scientific return of NEAT-like missions in terms of number of detected exoplanets and their parameter distributions. The second aspect of the PhD is relative to the testbed, which mimics the NEAT telescope configuration. I am going to present the testbed itself, the data analysis methods and the results. An accuracy of 3e-4 pixel was obtained for the relative positions of artificial stars and we have determined that measures of pixel positions by the metrology is currently limited by stray light.

Opportunity Science Using the Juno Magnetometer Investigation Star Trackers

NASA Astrophysics Data System (ADS)

Joergensen, J. L.; Connerney, J. E.; Bang, A. M.; Denver, T.; Oliversen, R. J.; Benn, M.; Lawton, P.

2013-12-01

The magnetometer experiment onboard Juno is equipped with four non-magnetic star tracker camera heads, two of which reside on each of the magnetometer sensor optical benches. These are located 10 and 12 m from the spacecraft body at the end of one of the three solar panel wings. The star tracker, collectively referred to as the Advanced Stellar Compass (ASC), provides high accuracy attitude information for the magnetometer sensors throughout science operations. The star tracker camera heads are pointed +/- 13 deg off the spin vector, in the anti-sun direction, imaging a 13 x 20 deg field of view every ¼ second as Juno rotates at 1 or 2 rpm. The ASC is a fully autonomous star tracker, producing a time series of attitude quaternions for each camera head, utilizing a suite of internal support functions. These include imaging capabilities, autonomous object tracking, automatic dark-sky monitoring, and related capabilities; these internal functions may be accessed via telecommand. During Juno's cruise phase, this capability can be tapped to provide unique science and engineering data available along the Juno trajectory. We present a few examples of the JUNO ASC opportunity science here. As the Juno spacecraft approached the Earth-Moon system for the close encounter with the Earth on October 9, 2013, one of the ASC camera heads obtained imagery of the Earth-Moon system while the other three remained in full science (attitude determination) operation. This enabled the first movie of the Earth and Moon obtained by a spacecraft flying past the Earth in gravity assist. We also use the many artificial satellites in orbit about the Earth as calibration targets for the autonomous asteroid detection system inherent to the ASC autonomous star tracker. We shall also profile the zodiacal dust disk, using the interstellar image data, and present the outlook for small asteroid body detection and distribution being performed during Juno's passage from Earth flyby to Jovian orbit insertion.

Effect of Hospital Case Mix on the Hospital Consumer Assessment of Healthcare Providers and Systems Star Scores: Are All Stars the Same?

PubMed

Thiels, Cornelius A; Hanson, Kristine T; Yost, Kathleen J; Zielinski, Martin D; Habermann, Elizabeth B; Cima, Robert R

2016-10-01

We aimed to evaluate variations in patient experience measures across different surgical specialties and to assess the impact of further case-mix adjustment. Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) is a publicly reported survey of patients' hospital experiences that directly influence Medicare reimbursement. All adult surgical inpatients meeting criteria for HCAHPS sampling from 2013 to 2014 at a single academic center were identified. HCAHPS measures were analyzed according to published top-box and Star-rating methodologies, and were dichotomized ("high" vs "low"). Multivariable logistic regression was used to identify independent associations of high patient scores on various HCAHPS measures with specialty, diagnosis-related group complexity, cancer diagnosis, sex, and emergency admission after adjusting for HCAHPS case-mix adjusters (education, overall health status, language, and age). We identified 36,551 eligible patients, of which 30.8% (n = 11,273) completed HCAHPS. Women [odds ratio (OR) 0.78, 95% confidence interval (CI) 0.72-0.85, P < 0.001], complex cases (OR 0.90, 95% CI 0.82-0.99, P = 0.02), and emergency admissions (OR 0.67, 95% CI 0.55-0.82, P < 0.001) had lesser Star scores on adjusted analysis, whereas patients with a cancer diagnosis had greater Star scores (OR 1.15, 95% CI 1.03-1.29, P = 0.01). Using general surgery as the reference, the Star scores varied significantly across 12 specialties (range OR 0.65 for plastics to 1.29 for transplant surgery). Patient responses to individual composite scores (pain, care transition, physician, and nurse) varied by specialty. HCAHPS case-mix adjustment does not include adjustment for specialty or diagnosis, which may result in artificially lower scores for centers that provide a high level of complex care. Further research is needed to ensure that the HCAHPS is an unbiased comparison tool.

Psychometric Properties of the Japanese Version of the STarT Back Tool in Patients with Low Back Pain.

PubMed

Matsudaira, Ko; Oka, Hiroyuki; Kikuchi, Norimasa; Haga, Yuri; Sawada, Takayuki; Tanaka, Sakae

2016-01-01

The STarT Back Tool uses prognostic indicators to classify patients with low back pain into three risk groups to guide early secondary prevention in primary care. The present study aimed to evaluate the psychometric properties of the Japanese version of the tool (STarT-J). An online survey was conducted among Japanese patients with low back pain aged 20-64 years. Reliability was assessed by examining the internal consistency of the overall and psychosocial subscales using Cronbach's alpha coefficients. Spearman's correlation coefficients were used to evaluate the concurrent validity between the STarT-J total score/psychosocial subscore and standard reference questionnaires. Discriminant validity was evaluated by calculating the area under the curves (AUCs) for the total and psychosocial subscale scores against standard reference cases. Known-groups validity was assessed by examining the relationship between low back pain-related disability and STarT-J scores. The analysis included data for 2000 Japanese patients with low back pain; the mean (standard deviation [SD]) age was 47.7 (9.3) years, and 54.1% were male. The mean (SD) STarT-J score was 2.2 (2.1). The Cronbach's alpha coefficient was 0.75 for the overall scale and 0.66 for the psychosocial subscale. Spearman's correlation coefficients ranged from 0.30 to 0.59, demonstrating moderate to strong concurrent validity. The AUCs for the total score ranged from 0.65 to 0.83, mostly demonstrating acceptable discriminative ability. For known-groups validity, participants with more somatic symptoms had higher total scores. Those in higher STarT-J risk groups had experienced more low back pain-related absences. The overall STarT-J scale was internally consistent and had acceptable concurrent, discriminant, and known-groups validity. The STarT-J can be used with Japanese patients with low back pain.

Photodetectors on Coronagraph Mask for Pointing Control

NASA Technical Reports Server (NTRS)

Balasubramanian, Kunjithapatham

2007-01-01

It has been proposed to install a symmetrical array of photodetectors about the center of the mask of a coronagraph of the type used to search for planets orbiting remote stars. The purpose of this installation is to utilize the light from a star under observation as a guide in pointing the telescope. Simple arithmetic processing of the outputs of the photodetectors would provide indications of the lateral position of the center of the mask relative to the center of the image of the star. These indications could serve as pointing-control feedback signals for adjusting the telescope aim to center the image of the star on the mask. The widths of central mask areas available for placement of photodetectors differ among coronagraph designs, typically ranging upward from about 100 m. Arrays of photodetectors can readily be placed within areas in this size range. The number of detectors in an array could be as small as 4 or as large as 64. The upper limit on the number of detectors would be determined according to the extent of the occulting pattern and the number of functionalities, in addition to pointing control, to be served by the array.

The structure and energy balance of cool star atmospheres

NASA Technical Reports Server (NTRS)

Linsky, J. L.

1982-01-01

The atmospheric structure and energy balance phenomena associated with magnetic fields in the Sun are reviewed and it is shown that similar phenomena occur in cool stars. The evidence for the weakening or disappearance of transition regions and coronae is discussed together with the appearance of extended cool chromospheres with large mass loss, near V-R = 0.80 in the H-R diagram. Like the solar atmosphere, these atmospheres are not homogeneous and there is considerable evidence for plage regions with bright TR emission lines that overlie dark (presumably magnetic) star spots. The IUE observations are providing important information on the energy balance in these atmospheres that should guide theoretical calculations of the nonradiative heating rate. Recent high dispersion spectra are providing unique information concerning which components of close binary systems are the dominant contributors to the observed emission. A recent unanticipated discovery is that the transition lines are redshifted (an antiwind) in DRa (G2 Ib) and perhaps other stars. Finally, the G and K giants and supergiants are classified into three groups depending on whether their atmospheres are dominated by closed magnetic flux tubes, open field geometries, or a predominately open geometry with a few closed flux tubes embedded.

Structure–function studies of STAR family Quaking proteins bound to their in vivo RNA target sites

PubMed Central

Teplova, Marianna; Hafner, Markus; Teplov, Dmitri; Essig, Katharina; Tuschl, Thomas; Patel, Dinshaw J.

2013-01-01

Mammalian Quaking (QKI) and its Caenorhabditis elegans homolog, GLD-1 (defective in germ line development), are evolutionarily conserved RNA-binding proteins, which post-transcriptionally regulate target genes essential for developmental processes and myelination. We present X-ray structures of the STAR (signal transduction and activation of RNA) domain, composed of Qua1, K homology (KH), and Qua2 motifs of QKI and GLD-1 bound to high-affinity in vivo RNA targets containing YUAAY RNA recognition elements (RREs). The KH and Qua2 motifs of the STAR domain synergize to specifically interact with bases and sugar-phosphate backbones of the bound RRE. Qua1-mediated homodimerization generates a scaffold that enables concurrent recognition of two RREs, thereby plausibly targeting tandem RREs present in many QKI-targeted transcripts. Structure-guided mutations reduced QKI RNA-binding affinity in vitro and in vivo, and expression of QKI mutants in human embryonic kidney cells (HEK293) significantly decreased the abundance of QKI target mRNAs. Overall, our studies define principles underlying RNA target selection by STAR homodimers and provide insights into the post-transcriptional regulatory function of mammalian QKI proteins. PMID:23630077

Laser guide star pointing camera for ESO LGS Facilities

NASA Astrophysics Data System (ADS)

Bonaccini Calia, D.; Centrone, M.; Pedichini, F.; Ricciardi, A.; Cerruto, A.; Ambrosino, F.

2014-08-01

Every observatory using LGS-AO routinely has the experience of the long time needed to bring and acquire the laser guide star in the wavefront sensor field of view. This is mostly due to the difficulty of creating LGS pointing models, because of the opto-mechanical flexures and hysteresis in the launch and receiver telescope structures. The launch telescopes are normally sitting on the mechanical structure of the larger receiver telescope. The LGS acquisition time is even longer in case of multiple LGS systems. In this framework the optimization of the LGS systems absolute pointing accuracy is relevant to boost the time efficiency of both science and technical observations. In this paper we show the rationale, the design and the feasibility tests of a LGS Pointing Camera (LPC), which has been conceived for the VLT Adaptive Optics Facility 4LGSF project. The LPC would assist in pointing the four LGS, while the VLT is doing the initial active optics cycles to adjust its own optics on a natural star target, after a preset. The LPC allows minimizing the needed accuracy for LGS pointing model calibrations, while allowing to reach sub-arcsec LGS absolute pointing accuracy. This considerably reduces the LGS acquisition time and observations operation overheads. The LPC is a smart CCD camera, fed by a 150mm diameter aperture of a Maksutov telescope, mounted on the top ring of the VLT UT4, running Linux and acting as server for the client 4LGSF. The smart camera is able to recognize within few seconds the sky field using astrometric software, determining the stars and the LGS absolute positions. Upon request it returns the offsets to give to the LGS, to position them at the required sky coordinates. As byproduct goal, once calibrated the LPC can calculate upon request for each LGS, its return flux, its fwhm and the uplink beam scattering levels.

Status report on the Large Binocular Telescope's ARGOS ground-layer AO system

NASA Astrophysics Data System (ADS)

Hart, M.; Rabien, S.; Busoni, L.; Barl, L.; Beckmann, U.; Bonaglia, M.; Boose, Y.; Borelli, J. L.; Bluemchen, T.; Carbonaro, L.; Connot, C.; Deysenroth, M.; Davies, R.; Durney, O.; Elberich, M.; Ertl, T.; Esposito, S.; Gaessler, W.; Gasho, V.; Gemperlein, H.; Hubbard, P.; Kanneganti, S.; Kulas, M.; Newman, K.; Noenickx, J.; Orban de Xivry, G.; Peter, D.; Quirrenbach, A.; Rademacher, M.; Schwab, C.; Storm, J.; Vaitheeswaran, V.; Weigelt, G.; Ziegleder, J.

2011-10-01

ARGOS, the laser-guided adaptive optics system for the Large Binocular Telescope (LBT), is now under construction at the telescope. By correcting atmospheric turbulence close to the telescope, the system is designed to deliver high resolution near infrared images over a field of 4 arc minute diameter. Each side of the LBT is being equipped with three Rayleigh laser guide stars derived from six 18 W pulsed green lasers and projected into two triangular constellations matching the size of the corrected field. The returning light is to be detected by wavefront sensors that are range gated within the seeing-limited depth of focus of the telescope. Wavefront correction will be introduced by the telescope's deformable secondary mirrors driven on the basis of the average wavefront errors computed from the respective guide star constellation. Measured atmospheric turbulence profiles from the site lead us to expect that by compensating the ground-layer turbulence, ARGOS will deliver median image quality of about 0.2 arc sec across the JHK bands. This will be exploited by a pair of multi-object near-IR spectrographs, LUCIFER1 and LUCIFER2, with 4 arc minute field already operating on the telescope. In future, ARGOS will also feed two interferometric imaging instruments, the LBT Interferometer operating in the thermal infrared, and LINC-NIRVANA, operating at visible and near infrared wavelengths. Together, these instruments will offer very broad spectral coverage at the diffraction limit of the LBT's combined aperture, 23 m in size.

Physical, chemical, and biological characteristics of the Boise River from Veterans Memorial Parkway, Boise to Star, Idaho, October 1987 to March 1988

USGS Publications Warehouse

Frenzel, S.A.

1988-01-01

Physical, chemical, and biological characteristics of the Boise River were examined from October 1987 to March 1988 to determine whether trace elements in effluents from two Boise wastewater treatment facilities were detrimental to aquatic communities. Cadmium, chromium, hexavalent chromium, cyanide, lead, nickel, and silver concentrations in the Boise River were less than or near analytical detection levels and were less than chronic toxicity criteria when detectable. Arsenic, copper, and zinc were detected in concentrations less than chronic toxicity criteria. Concentrations of trace elements in bottom material generally were small and could not be attributed to effluents from wastewater treatment facilities. From October to December 1987, mean density of benthic invertebrates colonizing artificial substrates was from 6,100 individuals/substrate downstream from the West Boise wastewater treatment facility to 14,000 individuals per substrate downstream from the Lander Street wastewater treatment facility. From January to March 1988 , mean density of benthic invertebrates colonizing artificial substrates was from 7,100 individuals per substrate downstream from the West Boise facility to 10,000 individuals per substrate near Star. Insect communities upstream and downstream from the wastewater treatment facilities were strongly associated, and coeffients of community loss indicated that effluents had benign enriching effects. Distribution of mayflies indicates that trace-element concentrations in effluents did not adversely affect intolerant organisms in the Boise River. Condition factor of whitefish was significantly increased downstream from the Lander Street wastewater treatment facility and was significantly decreased downstream from the West Boise wastewater treatment facility.

Spectral Classification of Galaxies at 0.5 <= z <= 1 in the CDFS: The Artificial Neural Network Approach

NASA Astrophysics Data System (ADS)

Teimoorinia, H.

2012-12-01

The aim of this work is to combine spectral energy distribution (SED) fitting with artificial neural network techniques to assign spectral characteristics to a sample of galaxies at 0.5 < z < 1. The sample is selected from the spectroscopic campaign of the ESO/GOODS-South field, with 142 sources having photometric data from the GOODS-MUSIC catalog covering bands between ~0.4 and 24 μm in 10-13 filters. We use the CIGALE code to fit photometric data to Maraston's synthesis spectra to derive mass, specific star formation rate, and age, as well as the best SED of the galaxies. We use the spectral models presented by Kinney et al. as targets in the wavelength interval ~1200-7500 Å. Then a series of neural networks are trained, with average performance ~90%, to classify the best SED in a supervised manner. We consider the effects of the prominent features of the best SED on the performance of the trained networks and also test networks on the galaxy spectra of Coleman et al., which have a lower resolution than the target models. In this way, we conclude that the trained networks take into account all the features of the spectra simultaneously. Using the method, 105 out of 142 galaxies of the sample are classified with high significance. The locus of the classified galaxies in the three graphs of the physical parameters of mass, age, and specific star formation rate appears consistent with the morphological characteristics of the galaxies.

SPECTRAL CLASSIFICATION OF GALAXIES AT 0.5 {<=} z {<=} 1 IN THE CDFS: THE ARTIFICIAL NEURAL NETWORK APPROACH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teimoorinia, H., E-mail: hteimoo@uvic.ca

2012-12-01

The aim of this work is to combine spectral energy distribution (SED) fitting with artificial neural network techniques to assign spectral characteristics to a sample of galaxies at 0.5 < z < 1. The sample is selected from the spectroscopic campaign of the ESO/GOODS-South field, with 142 sources having photometric data from the GOODS-MUSIC catalog covering bands between {approx}0.4 and 24 {mu}m in 10-13 filters. We use the CIGALE code to fit photometric data to Maraston's synthesis spectra to derive mass, specific star formation rate, and age, as well as the best SED of the galaxies. We use the spectralmore » models presented by Kinney et al. as targets in the wavelength interval {approx}1200-7500 A. Then a series of neural networks are trained, with average performance {approx}90%, to classify the best SED in a supervised manner. We consider the effects of the prominent features of the best SED on the performance of the trained networks and also test networks on the galaxy spectra of Coleman et al., which have a lower resolution than the target models. In this way, we conclude that the trained networks take into account all the features of the spectra simultaneously. Using the method, 105 out of 142 galaxies of the sample are classified with high significance. The locus of the classified galaxies in the three graphs of the physical parameters of mass, age, and specific star formation rate appears consistent with the morphological characteristics of the galaxies.« less

The application of digital medical 3D printing technology on tumor operation

NASA Astrophysics Data System (ADS)

Chen, Jimin; Jiang, Yijian; Li, Yangsheng

2016-04-01

Digital medical 3D printing technology is a new hi-tech which combines traditional medical and digital design, computer science, bio technology and 3D print technology. At the present time there are four levels application: The printed 3D model is the first and simple application. The surgery makes use of the model to plan the processing before operation. The second is customized operation tools such as implant guide. It helps doctor to operate with special tools rather than the normal medical tools. The third level application of 3D printing in medical area is to print artificial bones or teeth to implant into human body. The big challenge is the fourth level which is to print organs with 3D printing technology. In this paper we introduced an application of 3D printing technology in tumor operation. We use 3D printing to print guide for invasion operation. Puncture needles were guided by printed guide in face tumors operation. It is concluded that this new type guide is dominantly advantageous.

Hawaii Student / Teacher Astronomy Research program (HI STAR): 10 years of high school students exploring the universe

NASA Astrophysics Data System (ADS)

Mathews, Geoffrey; Armstrong, James; Nassir, Michael A.; Kaichi, Carolyn

2017-01-01

For the past decade, the Hawaii Student / Teacher Astronomy Research program (HI STAR) at UH Manoa’s Institute for Astronomy has trained astronomy-enthusiastic high school students in research, data analysis and science presentation skills. Every summer, a selected group of 8th-to-12th-grade students attend a week-long residential astronomy "camp" in Honolulu, Hawaii. The students experience the profession of astronomy by learning scientific skills such as imaging and spectroscopy, data-reduction, and data analysis. The week culminates with presention of a research project guided by professional astronomer mentors. During the following six months, each student continues to work with a mentor to complete a research project for submission to their local science fair. From 2012 - 2015, ~80% of students completed their long-term projects. Many have performed well; in each of 2015 and 2016, 5 alumni progressed to the International Science and Engineering Fair. Here we present the current structure of HI STAR and plans for the future.

The ultraviolet spectrum of noncoronal late-type stars - The Gamma Crucis (M3.4 III) reference spectrum

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth G.; Pesce, Joseph E.; Stencel, Robert E.; Brown, Alexander; Johansson, Sveneric

1988-01-01

A guide is presented to the UV spectrum of M-type giants and supergiants whose outer atmospheres contain warm chromospheres but not coronae. The M3 giant Gamma Crucis is taken as the archetype of the cooler, oxygen-rich, noncoronal stars. Line identifications and integrated line flux measurements of the chromospheric emission features seen in the 1200-3200 A range of IUE high-resolution spectra are presented. The major fluorescence processes operating in the outer atmosphere of Gamma Crucis, including eight previously unknown pumping processes and 21 new fluorescent line products, are summarized, and the enhancements of selected line strengths by 'line leakage' is discussed. A set of absorption features toward the longer wavelength end of this range is identified which can be used to characterize the radial velocity of the stellar photospheres. The applicability of the results to the spectra of noncoronal stars with different effective temperatures and gravities is discussed.

StarTrax --- The Next Generation User Interface

NASA Astrophysics Data System (ADS)

Richmond, Alan; White, Nick

StarTrax is a software package to be distributed to end users for installation on their local computing infrastructure. It will provide access to many services of the HEASARC, i.e. bulletins, catalogs, proposal and analysis tools, initially for the ROSAT MIPS (Mission Information and Planning System), later for the Next Generation Browse. A user activating the GUI will reach all HEASARC capabilities through a uniform view of the system, independent of the local computing environment and of the networking method of accessing StarTrax. Use it if you prefer the point-and-click metaphor of modern GUI technology, to the classical command-line interfaces (CLI). Notable strengths include: easy to use; excellent portability; very robust server support; feedback button on every dialog; painstakingly crafted User Guide. It is designed to support a large number of input devices including terminals, workstations and personal computers. XVT's Portability Toolkit is used to build the GUI in C/C++ to run on: OSF/Motif (UNIX or VMS), OPEN LOOK (UNIX), or Macintosh, or MS-Windows (DOS), or character systems.

Bioinspired Star-Shaped Poly(l-lysine) Polypeptides: Efficient Polymeric Nanocarriers for the Delivery of DNA to Mesenchymal Stem Cells.

PubMed

Walsh, David P; Murphy, Robert D; Panarella, Angela; Raftery, Rosanne M; Cavanagh, Brenton; Simpson, Jeremy C; O'Brien, Fergal J; Heise, Andreas; Cryan, Sally-Ann

2018-05-07

The field of tissue engineering is increasingly recognizing that gene therapy can be employed for modulating in vivo cellular response thereby guiding tissue regeneration. However, the field lacks a versatile and biocompatible gene delivery platform capable of efficiently delivering transgenes to mesenchymal stem cells (MSCs), a cell type often refractory to transfection. Herein, we describe the extensive and systematic exploration of three architectural variations of star-shaped poly(l-lysine) polypeptide (star-PLL) with varying number and length of poly(l-lysine) arms as potential nonviral gene delivery vectors for MSCs. We demonstrate that star-PLL vectors are capable of self-assembling with pDNA to form stable, cationic nanomedicines. Utilizing high content screening, live cell imaging, and mechanistic uptake studies we confirm the intracellular delivery of pDNA by star-PLLs to MSCs is a rapid process, which likely proceeds via a clathrin-independent mechanism. We identify a star-PLL composition with 64 poly(l-lysine) arms and five l-lysine subunits per arm as a particularly efficient vector that is capable of delivering both reporter genes and the therapeutic transgenes bone morphogenetic protein-2 and vascular endothelial growth factor to MSCs. This composition facilitated a 1000-fold increase in transgene expression in MSCs compared to its linear analogue, linear poly(l-lysine). Furthermore, it demonstrated comparable transgene expression to the widely used vector polyethylenimine using a lower pDNA dose with significantly less cytotoxicity. Overall, this study illustrates the ability of the star-PLL vectors to facilitate efficient, nontoxic nucleic acid delivery to MSCs thereby functioning as an innovative nanomedicine platform for tissue engineering applications.

Analysis of Dragon's Breath and Scattered Light Detector Anomalies on WFC3/UVIS

NASA Astrophysics Data System (ADS)

Fowler, Julia; Markwardt, Larissa; Bourque, Matthew; Anderson, Jay

2017-02-01

We summarize the examination of the light anomalies known as Dragon's Breath and Scattered Light for the UVIS channel of Wide Field Camera 3 (WFC3) of the Hubble Space Telescope (HST). We present three methods for WFC3 users to help avoid these effects during observation planning. We analyzed all of the full-frame wide and long pass filters with exposure times ≥ 300 seconds, comprising ∼13% of WFC3/UVIS on-orbit data (∼20% of all full-frame data, and ∼35% of all full-frame ≥300 second exposures.) We find that stars producing Dragon's Breath peak at specific orientations to the detector and V-band magnitudes. The bulk of these stars fall along the vertical and horizontal edges, within ∼490 pixels of the image frame. The corners of the detector show significantly fewer instances of Dragon's Breath and Scattered Light, though still a few occurrences. Furthermore, matching stars outside the field of the image to V-band magnitude data from the Hubble Guide Star Catalog II (GSC-II) shows that stars causing the anomaly consistently peak around a V-band magnitude of 11.9 or 14.6, whereas the general trend of objects lying outside the field instead peaks around a magnitude of 16.5 within our exposure time and filter selection.

Functional artificial luciferases as an optical readout for bioassays.

PubMed

Kim, Sung Bae; Izumi, Hiroshi

2014-06-13

This study elucidates functional artificial luciferases (ALucs) wholly synthesized for bioassays and molecular imaging. The ALucs bearing epitopes were newly created by amending the sequences of our previously reported ALucs in light of a multi-sequence alignment and hydrophobicity search. The synthesized ALucs are survived in live cells and stable in culture media for 25 days after secretion. The epitopes in ALucs are exposed during the secretion process and indeed valid for column purification and immunological assays. The ALucs exerted a 9400-times stronger optical intensity with a coelenterazine derivative (CTZ i), when compared with Renilla reniformis luciferase 8.6-535. A supersecondary structure of ALuc30 was predicted with respect to the X-ray crystallographic information of the coelenterazine-binding protein (CBP). The structure revealed that ALuc30 has a room for accommodating the iodide of CTZ i. This study guides on how to create functional artificial luciferases and predicts the structural details with the current bioinformatics technologies. Copyright © 2014 Elsevier Inc. All rights reserved.

Laser guide stars for optical free-space communications

NASA Astrophysics Data System (ADS)

Mata-Calvo, Ramon; Bonaccini Calia, Domenico; Barrios, Ricardo; Centrone, Mauro; Giggenbach, Dirk; Lombardi, Gianluca; Becker, Peter; Zayer, Igor

2017-02-01

The German Aerospace Center (DLR) and the European Southern Observatory (ESO) performed a measurement campaign together in April and July 2016 at Teide-Observatory (Tenerife), with the support of the European Space Agency (ESA), to investigate the use of laser guide stars (LGS) in ground to space optical communications. Atmospheric turbulence causes strong signal fluctuations in the uplink, due to scintillation and beam wander. In space communications, the use of the downlink channel as reference for pointing and for pre-distortion adaptive optics is limited by the size of the isokinetic and isoplanatic angle in relation to the required point-ahead angle. Pointing and phase errors due to the decorrelation between downward and upward beam due to the point-ahead angle may have a severe impact on the required transmit power and the stability of the communications link. LGSs provide a self-tailored reference to any optical ground-to-space link, independently of turbulence conditions and required point-ahead angle. In photon-starved links, typically in deep-space scenarios, LGSs allow dedicating all downlink received signal to communications purposes, increasing the available link margin. The scope of the joint DLR-ESO measurement campaign was, first, to measure the absolute value of the beam wander (uplink-tilt) using a LGS, taking a natural star as a reference, and, second, to characterize the decrease of correlation between uplink-tilt and downlink-tilt with respect to the angular separation between both sources. This paper describes the experiments performed during the measurement campaigns, providing an overview of the measured data and the first outcomes of the data post-processing.

Random generation of the turbulence slopes of a Shack-Hartmann wavefront sensor.

PubMed

Conan, Rodolphe

2014-03-15

A method to generate the turbulence measurements of a Shack-Hartmann wavefront sensor is presented. Numerical simulations demonstrate that the spatial and temporal statistic properties of the slopes are respected, allowing us to generate the turbulence wavefront gradient corresponding to both natural and laser guide stars, as well as time series in accordance with the frozen flow model.

PDSS/IMC CIS user's guide

NASA Technical Reports Server (NTRS)

1984-01-01

The Spacelab Payload Development Support System PDSS Image Motion Compensator (IMC) computer interface simulation (CIS) user's manual is given. The software provides a real time interface simulation for the following IMC subsystems: the Dry Rotor Reference Unit, the Advanced Star/Target Reference Optical sensor, the Ultra Violet imaging telescope, the Wisconson Ultraviolet Photopolarimetry Experiment, the Cruciform Power distributor, and the Spacelab Experiment Computer Operating System.

High Resolution Imaging Testbed Utilizing Sodium Laser Guide Star Adaptive Optics: The Real Time Wavefront Reconstructor Computer

DTIC Science & Technology

2008-07-31

Unlike the Lyrtech, each DSP on a Bittware board offers 3 MB of on-chip memory and 3 GFLOPs of 32-bit peak processing power. Based on the performance...Each NVIDIA 8800 Ultra features 576 GFLOPS on 128 612-MHz single-precision floating-point SIMD processors, arranged in 16 clusters of eight. Each

Claire Danes's Star-Body, Teen Female Viewers and the Pluralisation of Authorship in Baz Luhrmann's "William Shakespeare's Romeo + Juliet"

ERIC Educational Resources Information Center

Keam, Angela

2008-01-01

Teaching William Shakespeare's canonical tragedy "Romeo and Juliet" to teenagers in the context of the English classroom in Australia is not a particularly new pedagogical practice. In the year 2008, when many teachers (particularly those with a feminist bent such as I) are intent on guiding their students to decipher the ideological…

Thirty Meter Telescope narrow-field infrared adaptive optics system real-time controller prototyping results

NASA Astrophysics Data System (ADS)

Smith, Malcolm; Kerley, Dan; Chapin, Edward L.; Dunn, Jennifer; Herriot, Glen; Véran, Jean-Pierre; Boyer, Corinne; Ellerbroek, Brent; Gilles, Luc; Wang, Lianqi

2016-07-01

Prototyping and benchmarking was performed for the Real-Time Controller (RTC) of the Narrow Field InfraRed Adaptive Optics System (NFIRAOS). To perform wavefront correction, NFIRAOS utilizes two deformable mirrors (DM) and one tip/tilt stage (TTS). The RTC receives wavefront information from six Laser Guide Star (LGS) Shack- Hartmann WaveFront Sensors (WFS), one high-order Natural Guide Star Pyramid WaveFront Sensor (PWFS) and multiple low-order instrument detectors. The RTC uses this information to determine the commands to send to the wavefront correctors. NFIRAOS is the first light AO system for the Thirty Meter Telescope (TMT). The prototyping was performed using dual-socket high performance Linux servers with the real-time (PREEMPT_RT) patch and demonstrated the viability of a commercial off-the-shelf (COTS) hardware approach to large scale AO reconstruction. In particular, a large custom matrix vector multiplication (MVM) was benchmarked which met the required latency requirements. In addition all major inter-machine communication was verified to be adequate using 10Gb and 40Gb Ethernet. The results of this prototyping has enabled a CPU-based NFIRAOS RTC design to proceed with confidence and that COTS hardware can be used to meet the demanding performance requirements.

Laser guide star wavefront sensing for ground-layer adaptive optics on extremely large telescopes.

PubMed

Clare, Richard M; Le Louarn, Miska; Béchet, Clementine

2011-02-01

We propose ground-layer adaptive optics (GLAO) to improve the seeing on the 42 m European Extremely Large Telescope. Shack-Hartmann wavefront sensors (WFSs) with laser guide stars (LGSs) will experience significant spot elongation due to off-axis observation. This spot elongation influences the design of the laser launch location, laser power, WFS detector, and centroiding algorithm for LGS GLAO on an extremely large telescope. We show, using end-to-end numerical simulations, that with a noise-weighted matrix-vector-multiply reconstructor, the performance in terms of 50% ensquared energy (EE) of the side and central launch of the lasers is equivalent, the matched filter and weighted center of gravity centroiding algorithms are the most promising, and approximately 10×10 undersampled pixels are optimal. Significant improvement in the 50% EE can be observed with a few tens of photons/subaperture/frame, and no significant gain is seen by adding more than 200 photons/subaperture/frame. The LGS GLAO is not particularly sensitive to the sodium profile present in the mesosphere nor to a short-timescale (less than 100 s) evolution of the sodium profile. The performance of LGS GLAO is, however, sensitive to the atmospheric turbulence profile.

Guide star catalogue data retrieval software 2

NASA Technical Reports Server (NTRS)

Smirnov, O. M.; Malkov, O. YU.

1992-01-01

The Guide Star Catalog (GSC), being the largest astronomical catalog to date, is widely used by the astronomical community for all sorts of applications, such as statistical studies of certain sky regions, searches for counterparts to observational phenomena, and generation of finder charts. It's format (2 CD-ROM's) requires minimum hardware and is ideally suited for all sorts of conditions, especially observations. Unfortunately, the actual GSC data is not easily accessible. It takes the form of FITS tables, and the coordinates of the objects are given in one coordinate system (equinox 2000). The included reading software is rudimentary at best. Thus, even generation of a simple finder chart is not a trivial undertaking. To solve this problem, at least for PC users, GUIDARES was created. GUIDARES is a user-friendly program that lets you look directly at the data in the GSC, either as a graphical sky map or as a text table. GUIDARES can read a sampling of GSC data from a given sky region, store this sampling in a text file, and display a graphical map of the sampled region in projected celestial coordinates (perfect for finder charts). GUIDARES supports rectangular and circular regions defined by coordinates in the equatorial, ecliptic (any equinox) or galactic systems.

MagAO: status and science

NASA Astrophysics Data System (ADS)

Morzinski, Katie M.; Close, Laird M.; Males, Jared R.; Hinz, Phil M.; Esposito, Simone; Riccardi, Armando; Briguglio, Runa; Follette, Katherine B.; Pinna, Enrico; Puglisi, Alfio; Vezilj, Jennifer; Xompero, Marco; Wu, Ya-Lin

2016-07-01

"MagAO" is the adaptive optics instrument at the Magellan Clay telescope at Las Campanas Observatory, Chile. MagAO has a 585-actuator adaptive secondary mirror and 1000-Hz pyramid wavefront sensor, operating on natural guide stars from R-magnitudes of -1 to 15. MagAO has been in on-sky operation for 166 nights since installation in 2012. MagAO's unique capabilities are simultaneous imaging in the visible and infrared with VisAO and Clio, excellent performance at an excellent site, and a lean operations model. Science results from MagAO include the first ground-based CCD image of an exoplanet, demonstration of the first accreting protoplanets, discovery of a new wide-orbit exoplanet, and the first empirical bolometric luminosity of an exoplanet. We describe the status, report the AO performance, and summarize the science results. New developments reported here include color corrections on red guide stars for the wavefront sensor; a new field stop stage to facilitate VisAO imaging of extended sources; and eyepiece observing at the visible-light diffraction limit of a 6.5-m telescope. We also discuss a recent hose failure that led to a glycol coolant leak, and the recovery of the adaptive secondary mirror (ASM) after this recent (Feb. 2016) incident.

Configuration optimization of laser guide stars and wavefront correctors for multi-conjugation adaptive optics

NASA Astrophysics Data System (ADS)

Xuan, Li; He, Bin; Hu, Li-Fa; Li, Da-Yu; Xu, Huan-Yu; Zhang, Xing-Yun; Wang, Shao-Xin; Wang, Yu-Kun; Yang, Cheng-Liang; Cao, Zhao-Liang; Mu, Quan-Quan; Lu, Xing-Hai

2016-09-01

Multi-conjugation adaptive optics (MCAOs) have been investigated and used in the large aperture optical telescopes for high-resolution imaging with large field of view (FOV). The atmospheric tomographic phase reconstruction and projection of three-dimensional turbulence volume onto wavefront correctors, such as deformable mirrors (DMs) or liquid crystal wavefront correctors (LCWCs), is a very important step in the data processing of an MCAO’s controller. In this paper, a method according to the wavefront reconstruction performance of MCAO is presented to evaluate the optimized configuration of multi laser guide stars (LGSs) and the reasonable conjugation heights of LCWCs. Analytical formulations are derived for the different configurations and are used to generate optimized parameters for MCAO. Several examples are given to demonstrate our LGSs configuration optimization method. Compared with traditional methods, our method has minimum wavefront tomographic error, which will be helpful to get higher imaging resolution at large FOV in MCAO. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174274, 11174279, 61205021, 11204299, 61475152, and 61405194) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.

GeMS: Gemini Mcao System: current status and commissioning plans

NASA Astrophysics Data System (ADS)

Boccas, Maxime; Rigaut, François; Gratadour, Damien; d'Orgeville, Céline; Bec, Matthieu; Daruich, Felipe; Perez, Gabriel; Arriagada, Gustavo; Bombino, Stacy; Carter, Chris; Cavedoni, Chas; Collao, Fabian; Collins, Paul; Diaz, Pablo; Ebbers, Angelic; Galvez, Ramon; Gausachs, Gaston; Hardash, Steve; James, Eric; Karewicz, Stan; Lazo, Manuel; Maltes, Diego; Mouser, Ron; Rogers, Rolando; Rojas, Roberto; Sheehan, Michael; Trancho, Gelys; Vergara, Vicente; Vucina, Tomislav

2008-07-01

The Gemini Multi-Conjugate Adaptive Optics project was launched in April 1999 to become the Gemini South AO facility in Chile. The system includes 5 laser guide stars, 3 natural guide stars and 3 deformable mirrors optically conjugated at 0, 4.5 and 9km to achieve near-uniform atmospheric compensation over a 1 arc minute square field of view. Sub-contracted systems with vendors were started as early as October 2001 and were all delivered by July 2007, but for the 50W laser (due around September 2008). The in-house development began in January 2006, and is expected to be completed by the end of 2008 to continue with integration and testing (I&T) on the telescope. The on-sky commissioning phase is scheduled to start during the first half of 2009. In this general overview, we will first describe the status of each subsystem with their major requirements, risk areas and achieved performance. Next we will present our plan to complete the project by reviewing the remaining steps through I&T and commissioning on the telescope, both during day-time and at night-time. Finally, we will summarize some management activities like schedules, resources and conclude with some lessons learned.

Status of the ARGOS project

NASA Astrophysics Data System (ADS)

Rabien, Sebastian; Barl, Lothar; Beckmann, Udo; Bonaglia, Marco; Borelli, José Luis; Brynnel, Joar; Buschkamp, Peter; Busoni, Lorenzo; Christou, Julian; Connot, Claus; Davies, Richard; Deysenroth, Matthias; Esposito, Simone; Gässler, Wolfgang; Gemperlein, Hans; Hart, Michael; Kulas, Martin; Lefebvre, Michael; Lehmitz, Michael; Mazzoni, Tommaso; Nussbaum, Edmund; Orban de Xivry, Gilles; Peter, Diethard; Quirrenbach, Andreas; Raab, Walfried; Rahmer, Gustavo; Storm, Jesper; Ziegleder, Julian

2014-07-01

ARGOS is the Laser Guide Star and Wavefront sensing facility for the Large Binocular Telescope. With first laser light on sky in 2013, the system is currently undergoing commissioning at the telescope. We present the overall status and design, as well as first results on sky. Aiming for a wide field ground layer correction, ARGOS is designed as a multi- Rayleigh beacon adaptive optics system. A total of six powerful pulsed lasers are creating the laser guide stars in constellations above each of the LBTs primary mirrors. With a range gated detection in the wavefront sensors, and the adaptive correction by the deformable secondary's, we expect ARGOS to enhance the image quality over a large range of seeing conditions. With the two wide field imaging and spectroscopic instruments LUCI1 and LUCI2 as receivers, a wide range of scientific programs will benefit from ARGOS. With an increased resolution, higher encircled energy, both imaging and MOS spectroscopy will be boosted in signal to noise by a large amount. Apart from the wide field correction ARGOS delivers in its ground layer mode, we already foresee the implementation of a hybrid Sodium with Rayleigh beacon combination for a diffraction limited AO performance.

Calibrating the SNfactory Integral Field Spectrograph (SNIFS) with SCALA

NASA Astrophysics Data System (ADS)

Küsters, Daniel; Lombardo, Simona; Kowalski, Marek; Aldering, Greg; Nordin, Jakob; Rigault, Mickael

2016-08-01

The SNIFS CALibration Apparatus (SCALA), a device to calibrate the Supernova Integral Field Spectrograph on the University Hawaii 2.2m telescope, was developed and installed in Spring 2014. SCALA produces an artificial planet with a diameter of 1° and a constant surface brightness. The wavelength of the beam can be tuned between 3200 Å and 10000 Å and has a bandwidth of 35 Å. The amount of light injected into the telescope is monitored with NIST calibrated photodiodes. SCALA was upgraded in 2015 with a mask installed at the entrance pupil of the UH88 telescope, ensuring that the illumination of the telescope by stars is similar to that of SCALA. With this setup, a first calibration run was performed in conjunction with the spectrophotometric observations of standard stars. We present first estimates for the expected systematic uncertainties of the in-situ calibration and discuss the results of tests that examine the influence of stray light produced in the optics.

Characteristic Evolution and Matching

NASA Astrophysics Data System (ADS)

Winicour, Jeffrey

2012-01-01

I review the development of numerical evolution codes for general relativity based upon the characteristic initial-value problem. Progress in characteristic evolution is traced from the early stage of 1D feasibility studies to 2D-axisymmetric codes that accurately simulate the oscillations and gravitational collapse of relativistic stars and to current 3D codes that provide pieces of a binary black-hole spacetime. Cauchy codes have now been successful at simulating all aspects of the binary black-hole problem inside an artificially constructed outer boundary. A prime application of characteristic evolution is to extend such simulations to null infinity where the waveform from the binary inspiral and merger can be unambiguously computed. This has now been accomplished by Cauchy-characteristic extraction, where data for the characteristic evolution is supplied by Cauchy data on an extraction worldtube inside the artificial outer boundary. The ultimate application of characteristic evolution is to eliminate the role of this outer boundary by constructing a global solution via Cauchy-characteristic matching. Progress in this direction is discussed.

Assembling the Anthropocene: deep-time perspective on the development of a lithostratigraphic classification of Anthropogenic deposits and excavations

NASA Astrophysics Data System (ADS)

Waters, C. N.; Ford, J. R.; Price, S.; Cooper, A. H.

2012-12-01

Human modification of the Earth's surface/subsurface is associated with artificial deposits (anthropogenic sedimentary units) and excavated ground (anthropogenic unconformities), analogous to ancient depositional systems. This study examines how artificial ground can be classified by the procedures used for natural deposits. Anthropogenic deposits have different characteristics to other parts of the stratigraphic column: 1) they vary greatly in lateral and vertical extent; 2) they are strictly allostratigraphic, i.e. defined and identified by bounding discontinuities, either unconformities (e.g. artificial deposits resting directly upon bedrock), disconformities (e.g. a time-gap between parallel artificial strata associated with non-deposition or reworking) or the present-day land surface; 3) many units have no overlying strata or bounding surface; 4) they are often poorly exposed, though associated landforms/geomorphology may show characteristic features that can aid definition. Artificial deposits comprise modified geologic materials, e.g. sand, clay, coal and novel anthropogenic materials, e.g. plastic, brick, glass. Such deposits are typically heterogeneous, the lithology determined for practical purposes by current/former landuse activity. BGS maps for the UK use a five-fold morpho-stratigraphic subdivision with no lithological attribution. An enhanced BGS scheme (Price et al. 2011) uses a three-tier hierarchy to describe the origin and landform of the deposit or excavation with lithology and age treated as additional attributes. Though based largely on geomorphlogical expression and genetic origin, the scheme can be used for classifying subsurface deposits lacking landform expression. Anthropogenic modification ('anthropoturbation') of rock and natural sediments, e.g. boreholes, tunnels and mineshafts, may extend to significant depths. Although indicating the extent of human influence they do not affect the classification of the stratigraphy; analogous to post-depositional tectonics not resulting in renamed lithostratigraphic units. However, it may be necessary to classify large non-stratiform bodies, i.e. underground infilled cavities, as lithodemic units in a manner applicable to igneous intrusive rocks. A lithostratigraphic scheme for the Anthropocene should conform to international stratigraphic principles (Salvador 1994), each unit named after an appropriate geographic location and defined by a stratotype. Inclusion of a lithologic term is discouraged by Salvador (1994) and because of the inherent heterogeneity of artificial deposits would be unsuitable. However, additional morphologic/genetic epithets could be included for low ranking units. PRICE, S.J., FORD, J.R., COOPER, A.H. & NEAL, C. 2011. Humans as major geological and geomorphological agents in the Anthropocene: the significance of artificial ground in Great Britain. Philosophical Transactions of the Royal Society, A2011 369, 1056-1084. SALVADOR, A. 1994. International Stratigraphic Guide. A guide to stratigraphic classification, terminology, and procedure. 2nd Edition. The International Union of Geological Sciences and The Geological Society of America (Colorado). 214 pp.

The time course of spoken word learning and recognition: studies with artificial lexicons.

PubMed

Magnuson, James S; Tanenhaus, Michael K; Aslin, Richard N; Dahan, Delphine

2003-06-01

The time course of spoken word recognition depends largely on the frequencies of a word and its competitors, or neighbors (similar-sounding words). However, variability in natural lexicons makes systematic analysis of frequency and neighbor similarity difficult. Artificial lexicons were used to achieve precise control over word frequency and phonological similarity. Eye tracking provided time course measures of lexical activation and competition (during spoken instructions to perform visually guided tasks) both during and after word learning, as a function of word frequency, neighbor type, and neighbor frequency. Apparent shifts from holistic to incremental competitor effects were observed in adults and neural network simulations, suggesting such shifts reflect general properties of learning rather than changes in the nature of lexical representations.

Encoding and Decoding of Multi-Channel ICMS in Macaque Somatosensory Cortex.

PubMed

Dadarlat, Maria C; Sabes, Philip N

2016-01-01

Naturalistic control of brain-machine interfaces will require artificial proprioception, potentially delivered via intracortical microstimulation (ICMS). We have previously shown that multi-channel ICMS can guide a monkey reaching to unseen targets in a planar workspace. Here, we expand on that work, asking how ICMS is decoded into target angle and distance by analyzing the performance of a monkey when ICMS feedback was degraded. From the resulting pattern of errors, we found that the animal's estimate of target direction was consistent with a weighted circular-mean strategy-close to the optimal decoding strategy given the ICMS encoding. These results support our previous finding that animals can learn to use this artificial sensory feedback in an efficient and naturalistic manner.

De novo generation of plant centromeres at tandem repeats.

PubMed

Teo, Chee How; Lermontova, Inna; Houben, Andreas; Mette, Michael Florian; Schubert, Ingo

2013-06-01

Artificial minichromosomes are highly desirable tools for basic research, breeding, and biotechnology purposes. We present an option to generate plant artificial minichromosomes via de novo engineering of plant centromeres in Arabidopsis thaliana by targeting kinetochore proteins to tandem repeat arrays at non-centromeric positions. We employed the bacterial lactose repressor/lactose operator system to guide derivatives of the centromeric histone H3 variant cenH3 to LacO operator sequences. Tethering of cenH3 to non-centromeric loci led to de novo assembly of kinetochore proteins and to dicentric carrier chromosomes which potentially form anaphase bridges. This approach will be further developed and may contribute to generating minichromosomes from preselected genomic regions, potentially even in a diploid background.

Understanding Surface Adhesion in Nature: A Peeling Model.

PubMed

Gu, Zhen; Li, Siheng; Zhang, Feilong; Wang, Shutao

2016-07-01

Nature often exhibits various interesting and unique adhesive surfaces. The attempt to understand the natural adhesion phenomena can continuously guide the design of artificial adhesive surfaces by proposing simplified models of surface adhesion. Among those models, a peeling model can often effectively reflect the adhesive property between two surfaces during their attachment and detachment processes. In the context, this review summarizes the recent advances about the peeling model in understanding unique adhesive properties on natural and artificial surfaces. It mainly includes four parts: a brief introduction to natural surface adhesion, the theoretical basis and progress of the peeling model, application of the peeling model, and finally, conclusions. It is believed that this review is helpful to various fields, such as surface engineering, biomedicine, microelectronics, and so on.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cantrell, Justin R.; Henry, Todd J.; White, Russel J., E-mail: cantrell@chara.gsu.edu, E-mail: thenry@chara.gsu.edu, E-mail: white@chara.gsu.edu

We use the sample of known stars and brown dwarfs within 5 pc of the Sun, supplemented with AFGK stars within 10 pc, to determine which stellar spectral types provide the most habitable real estate—defined as locations where liquid water could be present on Earth-like planets. Stellar temperatures and radii are determined by fitting model spectra to spatially resolved broadband photometric energy distributions for stars in the sample. Using these values, the locations of the habitable zones are calculated using an empirical formula for planetary surface temperature and assuming the condition of liquid water, called here the empirical habitable zonemore » (EHZ). Systems that have dynamically disruptive companions are considered not habitable. We consider companions to be disruptive if the separation ratio of the companion to the habitable zone is less than 5:1. We use the results of these calculations to derive a simple formula for predicting the location of the EHZ for main sequence stars based on V – K color. We consider EHZ widths as more useful measures of the habitable real estate around stars than areas because multiple planets are not expected to orbit stars at identical stellar distances. This EHZ provides a qualitative guide on where to expect the largest population of planets in the habitable zones of main sequence stars. Because of their large numbers and lower frequency of short-period companions, M stars provide more EHZ real estate than other spectral types, possessing 36.5% of the habitable real estate en masse. K stars are second with 21.5%, while A, F, and G stars offer 18.5%, 6.9%, and 16.6%, respectively. Our calculations show that three M dwarfs within 10 pc harbor planets in their EHZs—GJ 581 may have two planets (d with msin i = 6.1 M {sub ⊕}; g with msin i = 3.1 M {sub ⊕}), GJ 667 C has one (c with msin i = 4.5 M {sub ⊕}), and GJ 876 has two (b with msin i = 1.89 M {sub Jup} and c with msin i = 0.56 M {sub Jup}). If Earth-like planets are as common around low-mass stars as recent Kepler results suggest, M stars will harbor more Earth-like planets in habitable zones than any other stellar spectral type.« less

Update On the Puzzling Boyajian's Star

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-09-01

Photometric time series for a neighboring star thats 25 NNW of Boyajians Star. No significant long-term dimming is seen which constrains the size of potential material obscuring Boyajians Star. [Wright et al. 2016/Benjamin Montet]Whats causing the mysterious light-curve dips of the so-called alien megastructure star, Boyajians Star? A recent study analyzes a variety of possible explanations to determine which ones are the most plausible.An Unusual Light CurveEarlier this year, astronomer Tabetha Boyajian reported on the unusual light curve of the star KIC 8462852. This star, now nicknamed Tabbys Star or Boyajians Star, showsunusual dips on day-long timescales that are too large to be explained by planet transits or similar phenomena.In addition to these short dips in luminosity, recent observations have also indicated that the star has faded by roughly 20% over the past hundred years. What could be causing both the short-term dips in the stars light and the long-term dimming over a century?Could the dimming be caused by an alien megastructure built by an extraterrestrial civilization? The authors find that a spherical structure is very unlikely. [Danielle Futselaar/SETI International]Alien Megastructures? Or Another Explanation?Boyajians Star was vaulted into the media spotlight when astronomer Jason Wright (Pennsylvania State University and University of California, Berkeley) proposed that its unusual light curve could potentially be explained by a surrounding megastructure built by an extraterrestrial civilization.Now Wright is back with co-author Steinn Sigurdsson (Pennsylvania State University). In a new study, Wright and Sigurdsson analyze an extensive list of explanations for the puzzling apparent behavior of Boyajians Star, based on our latest knowledge about this strange object.The Realm of PossibilitiesHere are just a few possible causes of Boyajians Stars dimming, as well as the authors assessment of their plausibility. For the full list, see the authors original article, or check out Wrights own summary of the article here!Pulsations, polar spots, and other stellar variability: unlikelyThe authors show that the variety of timescales observed for dimming events make scenarios involving stellar variations unlikely.Circumstellar material: unlikelyMaterial orbiting the star (like comets) would explain some of the light-curve dips, but it cant explain the long-term dimming observed.Post-merger return to normal: unclearPerhaps Boyajians Star recently merged with a brown dwarf or other star? Now it could be gradually dimming as it returns to its normal brightness, and restructuring of the stars material could causethe short-term dips. Though this scenariois possible, the timescales for the brightness changes are shorter than we would expect.Artificial structures: unclearSpherical swarms of structures would intercept the stars light and re-radiate it in infrared. Since long-wavelength observations have found no evidence of such radiation, the authors declare spherical geometries to be unlikely. Other structure geometries cant yet be ruled out, though.Small-scale interstellar medium (ISM) structure: plausibleSmall-scale density variations in the ISM between us and Boyajians Star could cause the dimming we observe, but the fact that nearby stars dont show similar dimming sets tight limits on the size of such ISM clumps.Spectral energy distribution of Boyajians Star. The upper-limit arrows on the right-hand side indicate that big clouds of megastructures are unlikely, because we would detect their heat as they re-radiate the stars light in infrared. [Wright et al. 2016]Looking to the FutureOf the possible locations for the source of the dimming, Wright and Sigurdsson deem the interstellar space between us and Boyajians Star to be the most likely culprit. They identify several future lines of research that could help us further eliminate possibilities, however, including a study of the ISM toward Boyajians Star, a hunt for similar variations in stars near in the sky to Boyajians Star, and infrared observation of the star with JWST to search for heat signatures.CitationJason T. Wright and Steinn Sigurdsson 2016 ApJ 829 L3. doi:10.3847/2041-8205/829/1/L3

Stellar spectral classification of previously unclassified stars GSC 4461-698 and GSC 4466-870

NASA Astrophysics Data System (ADS)

Grau, Darren Moser

Stellar spectral classification is one of the first efforts undertaken to begin defining the physical characteristics of stars. However, many stars lack even this basic information, which is the foundation for later research to constrain stellar effective temperatures, masses, radial velocities, the number of stars in the system, and age. This research obtained visible-λ stellar spectra via the testing and commissioning of a Santa Barbara Instruments Group (SBIG) Self-Guiding Spectrograph (SGS) at the UND Observatory. Utilizing a 16-inch-aperture telescope on Internet Observatory #3, the SGS obtained spectra of GSC 4461-698 and GSC 4466-870 in the low-resolution mode using an 18-µm wide slit with dispersion of 4.3 Å/pixel, resolution of 8 Å, and a spectral range from 3800-7500 Å. Observational protocols include automatic bias/dark frame subtraction for each stellar spectrum obtained. This was followed by spectral averaging to obtain a combined spectrum for each star observed. Image calibration and spectral averaging was performed using the software programs, Maxim DL, Image J, Microsoft Excel, and Winmk. A wavelength calibration process was used to obtain spectra of an Hg/Ne source that allowed the conversion of spectrograph channels into wavelengths. Stellar emission and absorption lines, such as those for hydrogen (H) and helium (He), were identified, extracted, and rectified. Each average spectrum was compared to the MK stellar spectral standards to determine an initial spectral classification for each star. The hope is that successful completion of this project will allow long-term stellar spectral observations to begin at the UND Observatory.

"Journey to the Stars": Presenting What Stars Are to Global Planetarium Audiences by Blending Astrophysical Visualizations Into a Single Immersive Production at the American Museum of Natural History

NASA Astrophysics Data System (ADS)

Emmart, Carter; Mac Low, M.; Oppenheimer, B. R.; Kinzler, R.; Paglione, T. A. D.; Abbott, B. P.

2010-01-01

"Journey to the Stars" is the latest and fourth space show based on storytelling from data visualization at the Rose Center for Earth and Space at the American Museum of Natural History. This twenty five minute, full dome movie production presents to planetarium audiences what the stars are, where they come from, how they vary in type and over time, and why they are important to life of Earth. Over forty scientists from around the world contributed their research to what is visualized into roughly fifteen major scenes. How this production is directed into a consolidated immersive informal science experience with learning goals is an integrative process with many inputs and concerns for scientific accuracy. The goal is a seamless merger of visualizations at varying spatial and temporal scales with acuity toward depth perception, revealing unseen phenomena, and the layering of concepts together to build an understanding of stars; to blend our common experience of them in the sky with the uncommon meaning we have come to know through science. Scripted by Louise Gikow who has worked for Children's Television Workshop, narrated by Whoopie Goldberg, and musically scored by Robert Miller, this production strives to guide audiences through challenging scientific concepts by complimenting the natural beauty the subject matter presents with understandable prose and musical grandeur. "Journey to the Stars" was produced in cooperation with NASA's Science Mission Directorate, Heliophysics Division and is in release at major planetariums, worldwide.

Artificial fish skin of self-powered micro-electromechanical systems hair cells for sensing hydrodynamic flow phenomena.

PubMed

Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Miao, Jianmin; Warkiani, Majid Ebrahimi; Triantafyllou, Michael S

2015-10-06

Using biological sensors, aquatic animals like fishes are capable of performing impressive behaviours such as super-manoeuvrability, hydrodynamic flow 'vision' and object localization with a success unmatched by human-engineered technologies. Inspired by the multiple functionalities of the ubiquitous lateral-line sensors of fishes, we developed flexible and surface-mountable arrays of micro-electromechanical systems (MEMS) artificial hair cell flow sensors. This paper reports the development of the MEMS artificial versions of superficial and canal neuromasts and experimental characterization of their unique flow-sensing roles. Our MEMS flow sensors feature a stereolithographically fabricated polymer hair cell mounted on Pb(Zr(0.52)Ti(0.48))O3 micro-diaphragm with floating bottom electrode. Canal-inspired versions are developed by mounting a polymer canal with pores that guide external flows to the hair cells embedded in the canal. Experimental results conducted employing our MEMS artificial superficial neuromasts (SNs) demonstrated a high sensitivity and very low threshold detection limit of 22 mV/(mm s(-1)) and 8.2 µm s(-1), respectively, for an oscillating dipole stimulus vibrating at 35 Hz. Flexible arrays of such superficial sensors were demonstrated to localize an underwater dipole stimulus. Comparative experimental studies revealed a high-pass filtering nature of the canal encapsulated sensors with a cut-off frequency of 10 Hz and a flat frequency response of artificial SNs. Flexible arrays of self-powered, miniaturized, light-weight, low-cost and robust artificial lateral-line systems could enhance the capabilities of underwater vehicles. © 2015 The Author(s).

Artificial fish skin of self-powered micro-electromechanical systems hair cells for sensing hydrodynamic flow phenomena

PubMed Central

Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Miao, Jianmin; Warkiani, Majid Ebrahimi; Triantafyllou, Michael S.

2015-01-01

Using biological sensors, aquatic animals like fishes are capable of performing impressive behaviours such as super-manoeuvrability, hydrodynamic flow ‘vision’ and object localization with a success unmatched by human-engineered technologies. Inspired by the multiple functionalities of the ubiquitous lateral-line sensors of fishes, we developed flexible and surface-mountable arrays of micro-electromechanical systems (MEMS) artificial hair cell flow sensors. This paper reports the development of the MEMS artificial versions of superficial and canal neuromasts and experimental characterization of their unique flow-sensing roles. Our MEMS flow sensors feature a stereolithographically fabricated polymer hair cell mounted on Pb(Zr0.52Ti0.48)O3 micro-diaphragm with floating bottom electrode. Canal-inspired versions are developed by mounting a polymer canal with pores that guide external flows to the hair cells embedded in the canal. Experimental results conducted employing our MEMS artificial superficial neuromasts (SNs) demonstrated a high sensitivity and very low threshold detection limit of 22 mV/(mm s−1) and 8.2 µm s−1, respectively, for an oscillating dipole stimulus vibrating at 35 Hz. Flexible arrays of such superficial sensors were demonstrated to localize an underwater dipole stimulus. Comparative experimental studies revealed a high-pass filtering nature of the canal encapsulated sensors with a cut-off frequency of 10 Hz and a flat frequency response of artificial SNs. Flexible arrays of self-powered, miniaturized, light-weight, low-cost and robust artificial lateral-line systems could enhance the capabilities of underwater vehicles. PMID:26423435

Orbital motion (3rd revised and enlarged edition)

NASA Astrophysics Data System (ADS)

Roy, A. E.

The fundamental principles of celestial mechanics are discussed in an introduction for students of astronomy, aerospace engineering, and geography. Chapters are devoted to the dynamic structure of the universe, coordinate and timekeeping systems, the reduction of observational data, the two-body problem, the many-body problem, general and special perturbations, and the stability and evolution of the solar system. Consideration is given to lunar theory, artificial satellites, rocket dynamics and transfer orbits, interplanetary and lunar trajectories, orbit determination and interplanetary navigation, binaries and other few-body systems, and many-body systems of stars. Diagrams, graphs, tables, and problems with solutions are provided.

Animal behaviour: geomagnetic map used in sea-turtle navigation.

PubMed

Lohmann, Kenneth J; Lohmann, Catherine M F; Ehrhart, Llewellyn M; Bagley, Dean A; Swing, Timothy

2004-04-29

Migratory animals capable of navigating to a specific destination, and of compensating for an artificial displacement into unfamiliar territory, are thought to have a compass for maintaining their direction of travel and a map sense that enables them to know their location relative to their destination. Compasses are based on environmental cues such as the stars, the Sun, skylight polarization and magnetism, but little is known about the sensory mechanism responsible for the map sense. Here we show that the green sea-turtle (Chelonia mydas) has a map that is at least partly based on geomagnetic cues.

PUSHing core-collapse simulations to explosion

NASA Astrophysics Data System (ADS)

Fröhlich, C.; Perego, A.; Hempe, M.; Ebinger, K.; Eichler, M.; Casanova, J.; Liebendörfer, M.; Thielemann, F.-K.

2018-01-01

We report on the PUSH method for artificially triggering core-collapse supernova explosions of massive stars in spherical symmetry. The PUSH method increases the energy deposition in the gain region proportionally to the heavy flavor neutrino fluxes.We summarize the parameter dependence of the method and calibrate PUSH to reproduce SN 1987A observables. We identify a best-fit progenitor and set of parameters that fit the explosion properties of SN 1987A, assuming 0.1 M⊙ of fallback. For the explored progenitor range of 18-21 M⊙, we find correlations between explosion properties and the compactness of the progenitor model.

StarNet: An application of deep learning in the analysis of stellar spectra

NASA Astrophysics Data System (ADS)

Kielty, Collin; Bialek, Spencer; Fabbro, Sebastien; Venn, Kim; O'Briain, Teaghan; Jahandar, Farbod; Monty, Stephanie

2018-06-01

In an era when spectroscopic surveys are capable of collecting spectra for hundreds of thousands of stars, fast and efficient analysis methods are required to maximize scientific impact. These surveys provide a homogeneous database of stellar spectra that are ideal for machine learning applications. In this poster, we present StarNet: a convolutional neural network model applied to the analysis of both SDSS-III APOGEE DR13 and synthetic stellar spectra. When trained on synthetic spectra alone, the calculated stellar parameters (temperature, surface gravity, and metallicity) are of excellent precision and accuracy for both APOGEE data and synthetic data, over a wide range of signal-to-noise ratios. While StarNet was developed using the APOGEE observed spectra and corresponding ASSeT synthetic grid, we suggest that this technique is applicable to other spectral resolutions, spectral surveys, and wavelength regimes. As a demonstration of this, we present a StarNet model trained on lower resolution, R=6000, IR synthetic spectra, describing the spectra delivered by Gemini/NIFS and the forthcoming Gemini/GIRMOS instrument (PI Sivanandam, UToronto). Preliminary results suggest that the stellar parameters determined from this low resolution StarNet model are comparable in precision to the high-resolution APOGEE results. The success of StarNet at lower resolution can be attributed to (1) a large training set of synthetic spectra (N ~200,000) with a priori stellar labels, and (2) the use of the entire spectrum in the solution rather than a few weighted windows, which are common methods in other spectral analysis tools (e.g. FERRE or The Cannon). Remaining challenges in our StarNet applications include rectification, continuum normalization, and wavelength coverage. Solutions to these problems could be used to guide decisions made in the development of future spectrographs, spectroscopic surveys, and data reduction pipelines, such as for the future MSE.

Highly accurate quantitative spectroscopy of massive stars in the Galaxy

NASA Astrophysics Data System (ADS)

Nieva, María-Fernanda; Przybilla, Norbert

2017-11-01

Achieving high accuracy and precision in stellar parameter and chemical composition determinations is challenging in massive star spectroscopy. On one hand, the target selection for an unbiased sample build-up is complicated by several types of peculiarities that can occur in individual objects. On the other hand, composite spectra are often not recognized as such even at medium-high spectral resolution and typical signal-to-noise ratios, despite multiplicity among massive stars is widespread. In particular, surveys that produce large amounts of automatically reduced data are prone to oversight of details that turn hazardous for the analysis with techniques that have been developed for a set of standard assumptions applicable to a spectrum of a single star. Much larger systematic errors than anticipated may therefore result because of the unrecognized true nature of the investigated objects, or much smaller sample sizes of objects for the analysis than initially planned, if recognized. More factors to be taken care of are the multiple steps from the choice of instrument over the details of the data reduction chain to the choice of modelling code, input data, analysis technique and the selection of the spectral lines to be analyzed. Only when avoiding all the possible pitfalls, a precise and accurate characterization of the stars in terms of fundamental parameters and chemical fingerprints can be achieved that form the basis for further investigations regarding e.g. stellar structure and evolution or the chemical evolution of the Galaxy. The scope of the present work is to provide the massive star and also other astrophysical communities with criteria to evaluate the quality of spectroscopic investigations of massive stars before interpreting them in a broader context. The discussion is guided by our experiences made in the course of over a decade of studies of massive star spectroscopy ranging from the simplest single objects to multiple systems.

Modeling Type II-P/II-L Supernovae Interacting with Recent Episodic Mass Ejections from Their Presupernova Stars with MESA and SNEC

NASA Astrophysics Data System (ADS)

Das, Sanskriti; Ray, Alak

2017-12-01

We show how dense, compact, discrete shells of circumstellar gas immediately outside of red supergiants affect the optical light curves of Type II-P/II-L supernovae (SNe), using the example of SN 2013ej. Earlier efforts in the literature had used an artificial circumstellar medium (CSM) stitched to the surface of an evolved star that had not gone through a phase of late-stage heavy mass loss, which, in essence, is the original source of the CSM. In contrast, we allow enhanced mass-loss rate from the modeled star during the 16O and 28Si burning stages and construct the CSM from the resulting mass-loss history in a self-consistent way. Once such evolved pre-SN stars are exploded, we find that the models with early interaction between the shock and the dense CSM reproduce light curves far better than those without that mass loss and, hence, having no nearby dense CSM. The required explosion energy for the progenitors with a dense CSM is reduced by almost a factor of two compared to those without the CSM. Our model, with a more realistic CSM profile and presupernova and explosion parameters, fits observed data much better throughout the rise, plateau, and radioactive tail phases as compared to previous studies. This points to an intermediate class of supernovae between Type II-P/II-L and Type II-n SNe with the characteristics of simultaneous UV and optical peak, slow decline after peak, and a longer plateau.

Life cycle of the multiarmed sea star Coscinasterias acutispina (Stimpson, 1862) in laboratory culture: sexual and asexual reproductive pathways.

PubMed

Shibata, Daisuke; Hirano, Yoshiaki; Komatsu, Miéko

2011-05-01

The multiarmed sea star Coscinasterias acutispina generally has 7-10 arms and 2-5 madreporites. It is known to be able to reproduce by asexual fission, and we have previously observed that this species also has the ability to reproduce sexually; however, there has been no report until now of spawning in this species. We succeeded in establishing a long-term culture of juveniles produced by artificial fertilization. Twelve months after the completion of metamorphosis, three individuals had six arms of the same length and a madreporite. At this time, fission occurred in two of these individuals, while the remaining individual underwent fission four months later. Each sea star divided into two halves, provided with three arms each. Thereafter, four or five new arms and two or four madreporites were formed anew in each of the six daughter sea-stars, so that by 30 days after the first fission the number of arms and madreporites in each was similar to that in adults. A second fission occurred in four of these six individuals, four or five months after the first fission, and in three of them the plane of division was the same as that of the first fission. The original three individuals eventually proliferated to 12 by undergoing fission. All individuals had fully developed gonads by 1-3 months after the second fission. Some of them eventually spawned under laboratory culture, and the resulting larvae metamorphosed into juveniles. Our observations demonstrate that individuals of C. acutispina possess the potential for both sexual and asexual reproduction.

ESO PR Highlights in 2007

NASA Astrophysics Data System (ADS)

2008-01-01

Another great year went by for ESO, the European Organisation for Astronomical Research in the Southern Hemisphere. From 1 January 2007, with the official joining of the Czech Republic, ESO has 13 member states, and since September, ESO has a new Director General, Tim de Zeeuw (ESO 03/07 and 38/07). Many scientific discoveries were made possible with ESO's telescopes. Arguably, the most important is the discovery of the first Earth-like planet in the habitable zone of a low-mass red dwarf (ESO 22/07). If there is water on this planet, then it should be liquid! ESO PR Highlights 2007 This is a clickable map. These are only some of the press releases issued by ESO in 2007. For a full listing, please go to ESO 2007 page. In our own Solar System also, astronomers made stunning breakthroughs with ESO's telescopes, observing the effect of the light from the Sun on an asteroid's rotation (ESO 11/07), describing in unprecedented detail the double asteroid Antiope (ESO 18/07), peering at the rings of Uranus (ESO 37/07), discovering a warm south pole on Neptune (ESO 41/07), showing a widespread and persistent morning drizzle of methane over the western foothills of Titan's major continent (ESO 47/07), and studying in the greatest details the wonderful Comet McNaught (ESO 05/07 and 07/07). In the study of objects slightly more massive than planets, the VLT found that brown dwarfs form in a similar manner to normal stars (ESO 24/07). The VLT made it also possible to measure the age of a fossil star that was clearly born at the dawn of time (ESO 23/07). Other discoveries included reconstructing the site of a flare on a solar-like star (ESO 53/07), catching a star smoking (ESO 34/07), revealing a reservoir of dust around an elderly star (ESO 43/07), uncovering a flat, nearly edge-on disc of silicates in the heart of the magnificent Ant Nebula (ESO 42/07), finding material around a star before it exploded (ESO 31/07), fingerprinting the Milky Way (ESO 15/07), revealing a rich circular cluster of stars (ESO 12/07), hunting galaxies (ESO 40/07), discovering teenage galaxies (ESO 52/07), and finding the first known triplet of supermassive black holes (ESO 02/07). On the instrumentation side, the VLT has been equipped with a new 'eye' to study the Universe in the near-infrared, Hawk-I (ESO 36/07), while the Laser Guide Star used at the VLT to create an artificial star appears to fulfil all its promises (ESO 27/07 and 33/07). Successful tests were also done of a crucial technology for Extremely Large Telescopes (ESO 19/07). The VLT Rapid Response Mode showed it unique capabilities in the study of gamma-ray bursts (ESO 17/07), as did the REM, a robotic telescope at La Silla, that allowed astronomers to measure for the first time the speed of matter ejected in these tremendous explosions (ESO 26/07). The world's largest bolometer camera for submillimetre astronomy, LABOCA, is now in service at the 12-m APEX telescope (ESO 35/07), while the construction of ALMA moves forwards. Two 12-m ALMA prototype antennas were first linked together as an integrated system to observe an astronomical object (ESO 10/07), the ALMA Operations Support Facility is almost completed (ESO 13/07), and the ALMA transporters were shipped to Chile (ESO 32/07 and 45/07). ESO is also present on the educational front with, for example, its annual international contest for students, Catch a Star (ESO 21/07 and 46/07). In April 2007, ESO organised with its partners the second EIROforum Science on Stage festival, a unique event, showcasing the very best of today's science education and to which participated the European Commissioner for Science and Research, Janez Potočnik. The Commissioner also visited the Paranal observatory (ESO 48/07) and took part in the observation of a beautiful galaxy (ESO 49/07). This was not the only nice image coming out from ESO telescopes. A rather amazing Cosmic Bird - or a gigantic Tinker Bell - was photographed (ESO 55/07), as well as a Purple Rose (ESO 16/07) and a stellar firework (ESO 39/07). And last but least, at the end of the year, the United Nations passed a resolution proclaiming 2009 the International Year of Astronomy (ESO 54/07).

Visual Outcomes After LASIK Using Topography-Guided vs Wavefront-Guided Customized Ablation Systems.

PubMed

Toda, Ikuko; Ide, Takeshi; Fukumoto, Teruki; Tsubota, Kazuo

2016-11-01

To evaluate the visual performance of two customized ablation systems (wavefront-guided ablation and topography-guided ablation) in LASIK. In this prospective, randomized clinical study, 68 eyes of 35 patients undergoing LASIK were enrolled. Patients were randomly assigned to wavefront-guided ablation using the iDesign aberrometer and STAR S4 IR Excimer Laser system (Abbott Medical Optics, Inc., Santa Ana, CA) (wavefront-guided group; 32 eyes of 16 patients; age: 29.0 ± 7.3 years) or topography-guided ablation using the OPD-Scan aberrometer and EC-5000 CXII excimer laser system (NIDEK, Tokyo, Japan) (topography-guided group; 36 eyes of 19 patients; age: 36.1 ± 9.6 years). Preoperative manifest refraction was -4.92 ± 1.95 diopters (D) in the wavefront-guided group and -4.44 ± 1.98 D in the topography-guided group. Visual function and subjective symptoms were compared between groups before and 1 and 3 months after LASIK. Of seven subjective symptoms evaluated, four were significantly milder in the wavefront-guided group at 3 months. Contrast sensitivity with glare off at low spatial frequencies (6.3° and 4°) was significantly higher in the wavefront-guided group. Uncorrected and corrected distance visual acuity, manifest refraction, and higher order aberrations measured by OPD-Scan and iDesign were not significantly different between the two groups at 1 and 3 months after LASIK. Both customized ablation systems used in LASIK achieved excellent results in predictability and visual function. The wavefront-guided ablation system may have some advantages in the quality of vision. It may be important to select the appropriate system depending on eye conditions such as the pattern of total and corneal higher order aberrations. [J Refract Surg. 2016;32(11):727-732.]. Copyright 2016, SLACK Incorporated.

Ancient Earth, Alien Earths Event

NASA Image and Video Library

2014-08-20

Dr. David H. Grinspoon, Senior Scientist, Planetary Science Institute, moderates a panel at the “Ancient Earth, Alien Earths” Event at NASA Headquarters in Washington, DC Wednesday, August 20, 2014. The event was sponsored by NASA, the National Science Foundation (NSF), and the Smithsonian Institution and highlighted how research on early Earth could help guide our search for habitable planets orbiting other stars. Photo Credit: (NASA/Aubrey Gemignani)

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The Building America team NorthernSTAR investigated opportunities to use the massive customer networks of the home service industry as a means to connect homeowners to home-performance solutions. Home service companies could provide a pathway to advance building-science-guided upgrades by being in close proximity to homeowners when a decision-making moment is at hand. Established trust provides an opportunity for the company to deliver sound information and influence during a remodeling decision.