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Sample records for leo npinen lo

  1. Leo

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    (the Lion; abbrev. Leo, gen. Leonis; area 947 sq. deg.) A northern zodiacal constellation which lies between Cancer and Virgo, and culminates at midnight in early March. It represents the Nemean lion that, in Greek mythology, Hercules killed as the first of his 12 labors. Its brightest stars were cataloged by Ptolemy (c. AD 100-175) in the Almagest....

  2. Leo Minor

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    (the Lesser Lion; abbrev. LMi, gen. Leonis Minoris; area 232 sq.deg.) A northern constellation which lies between Ursa Major and Leo, and culminates at midnight in late February. It was introduced by the astronomer Johannes Hevelius (1611-87) of Danzig (Gdansk), who included it in his atlas Firmamentum Sobiescianum sive Uranographia of 1687....

  3. The LEOS Interpolation Package

    SciTech Connect

    Fritsch, F N

    2003-03-12

    This report describes the interpolation package in the Livermore Equation of State (LEOS) system. It is an updated and expanded version of report [1], which described the status of the package as of May 1998, and of [2], which described its status as of the August 2001 release of the LEOS access library, and of [3], which described its status as of library version 7.02, released April 2002. This corresponds to library version 7.11, released March 2003. The main change since [3] has been the addition of the monotone bicubic Hermite (bimond) interpolation method. Throughout this report we assume that data has been given for some function f({rho},T) on a rectangular mesh {rho} = {rho}{sub 0}, {rho}{sub 1}, ..., {rho}{sub nr-1}; T = T{sub 0}, T{sub 1}, ..., T{sub nt-1}. Subscripting is from zero to be consistent with the C code. (Although we use this notation throughout, there is nothing in the package that assumes that the independent variables are actually density and temperature.) The data values are f{sub ij} = f({rho}{sub j},T{sub i}). (This subscript order is historical and reflects the notation used in the program.) There are nr x nt data values, (nr-1) x (nt-1) mesh rectangles (boxes). In the C code, the data array is one-dimensional, with data [i*(nr-1)+j] = f({rho}{sub j},T{sub i}). In the case of the few univariate functions supported by LEOS, the T variable is omitted, as well as the associated index on the data array: data [j] = f({rho}{sub j}).

  4. LEO Spacecraft Charging Guidelines

    NASA Technical Reports Server (NTRS)

    Hillard, G. B.; Ferguson, D. C.

    2002-01-01

    Over the past decade, Low Earth Orbiting (LEO) spacecraft have gradually required ever-increasing power levels. As a rule, this has been accomplished through the use of high voltage systems. Recent failures and anomalies on such spacecraft have been traced to various design practices and materials choices related to the high voltage solar arrays. NASA Glenn has studied these anomalies including plasma chamber testing on arrays similar to those that experienced difficulties on orbit. Many others in the community have been involved in a comprehensive effort to understand the problems and to develop practices to avoid them. The NASA Space Environments and Effects program, recognizing the timeliness of this effort, has commissioned and funded a design guidelines document intended to capture the current state of understanding. We present here an overview of this document, which is now nearing completion.

  5. Leo space plasma interactions

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.

    1991-01-01

    Photovoltaic arrays interact with the low earth orbit (LEO) space plasma in two fundamentally different ways. One way is the steady collection of current from the plasma onto exposed conductors and semiconductors. The relative currents collected by different parts of the array will then determine the floating potential of the spacecraft. In addition, these steady state collected currents may lead to sputtering or heating of the array by the ions or electrons collected, respectively. The second kind of interaction is the short time scale arc into the space plasma, which may deplete the array and/or spacecraft of stored charge, damage solar cells, and produce EMI. Such arcs only occur at high negative potentials relative to the space plasma potential, and depend on the steady state ion currents being collected. New high voltage solar arrays being incorporated into advanced spacecraft and space platforms may be endangered by these plasma interactions. Recent advances in laboratory testing and current collection modeling promise the capability of controlling, and perhaps even using, these space plasma interactions to enable design of reliable high voltage space power systems. Some of the new results may have an impact on solar cell spacing and/or coverslide design. Planned space flight experiments are necessary to confirm the models of high voltage solar array plasma interactions. Finally, computerized, integrated plasma interactions design tools are being constructed to place plasma interactions models into the hands of the spacecraft designer.

  6. GFEChutes Lo-Fi

    NASA Technical Reports Server (NTRS)

    Gist, Emily; Turner, Gary; Shelton, Robert; Vautier, Mana; Shaikh, Ashraf

    2013-01-01

    NASA needed to provide a software model of a parachute system for a manned re-entry vehicle. NASA has parachute codes, e.g., the Descent Simulation System (DSS), that date back to the Apollo Program. Since the space shuttle did not rely on parachutes as its primary descent control mechanism, DSS has not been maintained or incorporated into modern simulation architectures such as Osiris and Antares, which are used for new mission simulations. GFEChutes Lo-Fi is an object-oriented implementation of conventional parachute codes designed for use in modern simulation environments. The GFE (Government Furnished Equipment), low-fidelity (Lo-Fi) parachute model (GFEChutes Lo-Fi) is a software package capable of modeling the effects of multiple parachutes, deployed concurrently and/or sequentially, on a vehicle during the subsonic phase of reentry into planetary atmosphere. The term "low-fidelity" distinguishes models that represent the parachutes as simple forces acting on the vehicle, as opposed to independent aerodynamic bodies. GFEChutes Lo-Fi was created from these existing models to be clean, modular, certified as NASA Class C software, and portable, or "plug and play." The GFE Lo-Fi Chutes Model provides basic modeling capability of a sequential series of parachute activities. Actions include deploying the parachute, changing the reefing on the parachute, and cutting away the parachute. Multiple chutes can be deployed at any given time, but all chutes in that case are assumed to behave as individually isolated chutes; there is no modeling of any interactions between deployed chutes. Drag characteristics of a deployed chute are based on a coefficient of drag, the face area of the chute, and the local dynamic pressure only. The orientation of the chute is approximately modeled for purposes of obtaining torques on the vehicle, but the dynamic state of the chute as a separate entity is not integrated - the treatment is simply an approximation. The innovation in GFEChutes

  7. Mitochondrial genome of the African lion Panthera leo leo.

    PubMed

    Ma, Yue-ping; Wang, Shuo

    2015-01-01

    In this study, the complete mitochondrial genome sequence of the African lion P. leo leo was reported. The total length of the mitogenome was 17,054 bp. It contained the typical mitochondrial structure, including 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 1 control region; 21 of the tRNA genes folded into typical cloverleaf secondary structure except for tRNASe. The overall composition of the mitogenome was A (32.0%), G (14.5%), C (26.5%) and T (27.0%). The new sequence will provide molecular genetic information for conservation genetics study of this important large carnivore.

  8. Leo Tolstoy the Spiritual Educator

    ERIC Educational Resources Information Center

    Moulin, Dan

    2008-01-01

    This paper considers the often overlooked religious and educational works of the Russian novelist Leo Tolstoy (1828-1910). After outlining Tolstoy's life, religious and educational views, it is argued that Tolstoy has much to offer spiritual educators today. In particular, it suggests Tolstoy's insistence on the absolute and eternal nature of…

  9. The Year of Leo Lionni.

    ERIC Educational Resources Information Center

    McQuade, Molly

    1998-01-01

    Discusses the picture books of Leo Lionni and describes how Vivian Gussin Paley, a Chicago elementary school teacher, used his books for an entire year's curriculum in her kindergarten class. Highlights include children's engagement with literature, and other learning activities based on the books. (LRW)

  10. Wave optics-based LEO-LEO radio occultation retrieval

    NASA Astrophysics Data System (ADS)

    Benzon, Hans-Henrik; Høeg, Per

    2016-06-01

    This paper describes the theory for performing retrieval of radio occultations that use probing frequencies in the XK and KM band. Normally, radio occultations use frequencies in the L band, and GPS satellites are used as the transmitting source, and the occultation signals are received by a GPS receiver on board a Low Earth Orbit (LEO) satellite. The technique is based on the Doppler shift imposed, by the atmosphere, on the signal emitted from the GPS satellite. Two LEO satellites are assumed in the occultations discussed in this paper, and the retrieval is also dependent on the decrease in the signal amplitude caused by atmospheric absorption. The radio wave transmitter is placed on one of these satellites, while the receiver is placed on the other LEO satellite. One of the drawbacks of normal GPS-based radio occultations is that external information is needed to calculate some of the atmospheric products such as the correct water vapor content in the atmosphere. These limitations can be overcome when a proper selected range of high-frequency waves are used to probe the atmosphere. Probing frequencies close to the absorption line of water vapor have been included, thus allowing the retrieval of the water vapor content. Selecting the correct probing frequencies would make it possible to retrieve other information such as the content of ozone. The retrieval is performed through a number of processing steps which are based on the Full Spectrum Inversion (FSI) technique. The retrieval chain is therefore a wave optics-based retrieval chain, and it is therefore possible to process measurements that include multipath. In this paper simulated LEO to LEO radio occultations based on five different frequencies are used. The five frequencies are placed in the XK or KM frequency band. This new wave optics-based retrieval chain is used on a number of examples, and the retrieved atmospheric parameters are compared to the parameters from a global European Centre for Medium

  11. New NASA SEE LEO Spacecraft Charging Design Guidelines: How to Survive in LEO Rather Than GEO

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Hillard, G. Barry

    2003-01-01

    It has been almost two solar cycles since the 1984 GEO Guidelines of Purvis, Garrett, Whittlesey, and Stevens were published. In that time, interest in high voltage LEO systems has increased. Correct and conventional wisdom has been that LEO conditions are sufficiently different from GEO that the GEO Guidelines (and other GEO and POLAR documents produced since then) should not be used for LEO spacecraft. Because of significant recent GEO spacecraft failures that have been shown in ground testing to be likely to also occur on LEO spacecraft, the SEE program commissioned the production of the new LEO Spacecraft Charging Design Guidelines. Now available in CD-ROM form, the LEO Guidelines highlight mitigation techniques to prevent spacecraft arcing on LEO solar arrays and other systems. We compare and contrast the mitigation techniques for LEO and GEO in this paper. We also discuss the extensive bibliography included in the LEO Guidelines, so results can be found in their primary sources.

  12. Raising a Child in the Punana Leo

    ERIC Educational Resources Information Center

    Iokepa-Guerrero, Noelani

    2008-01-01

    At the Punana Leo everyone, "'Anakala", uncle--a male teacher, "'Anake," aunty--a female teacher, and the "keiki," children all play important roles in the educational program of the school. Each and all are responsible for the learning that takes place and the success of the program. In this article, the author describes the Punana Leo, the only…

  13. Michigan Turns to Leo Goldberg

    NASA Astrophysics Data System (ADS)

    Lindner, Rudi P.

    2006-12-01

    The death of Heber D. Curtis at the beginning of 1942 emphasized the difficult circumstances facing Michigan's astronomy program. There were no funds to figure or mount the 98" pyrex blank; the 37" reflector labored under floodlights; and the war sapped the graduate program. For a number of years the staff argued over the best path for the future, goaded by the unwelcome intervention of the "amateurs" McMath and Hulbert. The administration brought in outside consultants, attempted to prevent the observatory staff from making separate arrangements, trawled in western waters without success, and took conflicting advice on the future direction of the science. In 1946 the university leadership had, as well, to consider the aftermath of the war: new possibilities in physics, new funding opportunities, a booming student population, and the encapsulation of the observatory within the medical campus. At this time, Leo Goldberg was on the McMath-Hulbert staff, had little to do with the Ann Arbor community, and was considered to be an outsider, beholden to astrophysical theory and his promoters at Harvard. Leo Goldberg's rise from relative obscurity, his transformation from assistant to leader, and the university leadership's assessment of the possibilities for the transformation of a midwest, urban, and traditional program form the topic of this paper, based upon the Michigan and Harvard archives as well as the memories of Goldberg's cohort.

  14. Optimal trajectories for LEO-to-LEO aeroassisted orbital transfer

    NASA Astrophysics Data System (ADS)

    Miele, A.; Lee, W. Y.; Mease, K. D.

    This paper considers both classical and minimax problems of optimal control arising in the study of noncoplanar, aeroassisted orbital transfer. The maneuver considered involves the transfer from one planetary orbit to another having different orbital inclination, but the same radius. An example is the LEO-to-LEO transfer of a spacecraft with a prescribed plane change, where LEO denotes low Earth orbit. The basic idea is to employ the hybrid combination of propulsive maneuvers in space and aerodynamic maneuvers in the sensible atmosphere. Hence, this type of flight is also called synergetic space flight. With reference to the atmospheric part of the maneuver, trajectory control is achieved by modulating the lift coefficient (hence, the angle of attack) and the angle of bank. The presence of upper and lower bounds on the lift coefficient is considered. Three different transfer maneuvers are studied. Type 1 involves four impulses and four space plane changes; Type 2 involves three impulses and three space plane changes; and Type 3 involves three impulses and no space plane change. In Type 1, the initial impulse directs the spacecraft away from Earth, and then is followed by an apogee impulse propelling the spacecraft toward Earth; in Types 2 and 3, the initial impulse directs the spacecraft toward Earth. A common element of these maneuvers is that they all include an atmospheric pass, with velocity depletion coupled with plane change. Within the framework of classical optimal control, the following problems are studied: (P1) minimize the energy required for orbital transfer; (P4) maximize the time of flight during the atmospheric portion of the trajectory; (P5) minimize the time integral of the square of the path inclination. Within the framework of minimax optimal control, the following problem is studied: (Q1) minimize the peak heating rate. Numerical solutions for Problems (P1), (P4), (P5), (Q1) are obtained by means of the sequential gradient-restoration algorithm

  15. New NASA SEE LEO Spacecraft Charging Design Guidelines: How to Survive in LEO Rather than GEO

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Hillard, G. Barry

    2004-01-01

    It has been almost two solar cycles since the GEO Guidelines of Purvis et al (1984) were published. In that time, interest in high voltage LEO systems has increased. The correct and conventional wisdom has been that LEO conditions are sufficiently different from GEO that the GEO Guidelines (and other GEO and POLAR documents produced since then) should not be used for LEO spacecraft. Because of significant recent GEO spacecraft failures that have been shown in ground testing to be likely to also occur on LEO spacecraft, the SEE program commissioned the production of the new LEO Spacecraft Charging Design Guidelines (hereafter referred to as the LEO Guidelines). Now available in CD-ROM form, the LEO Guidelines highlight mitigation techniques to prevent spacecraft arcing on LEO solar arrays and other systems. We compare and contrast the mitigation techniques for LEO and GEO in this paper. We also discuss the extensive bibliography included in the LEO Guidelines, so results can be found in their primary sources.

  16. XML Format for SESAME and LEOS

    SciTech Connect

    Durrenberger, J K; Neely, J R; Sterne, P A

    2009-04-29

    The objective of this document is to describe the XML format used by LLNL and LANL to represent the equation-of-state and related material information in the LEOS and SESAME data libraries. The primary purpose of this document is to describe a specific XML format for representing EOS data that is tailored to the nature of the underlying data and is amenable to conversion to both legacy SESAME and LEOS binary formats. The secondary purpose is to describe an XML format that lends itself to a 'natural' representation in a binary file format of the SESAME, pdb or hdf5 form so that this format and related tools can be used for the rapid and efficient development and implementation of prototype data structures. This document describes the XML format only. A working knowledge of LEOS and SESAME formats is assumed.

  17. NASA STD-4005: The LEO Spacecraft Charging Design Standard

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.

    2006-01-01

    Power systems with voltages higher than about 55 volts may charge in Low Earth Orbit (LEO) enough to cause destructive arcing. The NASA STD-4005 LEO Spacecraft Charging Design Standard will help spacecraft designers prevent arcing and other deleterious effects on LEO spacecraft. The Appendices, an Information Handbook based on the popular LEO Spacecraft Charging Design Guidelines by Ferguson and Hillard, serve as a useful explanation and accompaniment to the Standard.

  18. NASA 4005: The LEO Spacecraft Charging Design Standard

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.

    2006-01-01

    Power systems with voltages higher than about 55 volts may charge in Low Earth Orbit (LEO) enough to cause destructive arcing. The NASA 4005 LEO Spacecraft Charging Design Standard will help spacecraft designers prevent arcing and other deleterious effects on LEO spacecraft. The appendices, based on the popular LEO Spacecraft Charging Design Guidelines by Ferguson and Hillard, serve as a useful information handbook to explain and accompany the standard.

  19. [Leo Sternbach, an inventor of benzodiazepines].

    PubMed

    Uchibayashi, Masao

    2007-01-01

    A biography of Leo Sternbach, an inventor of benzodiazepine tranquillizers, is presented. It consists of (1) a societal desire for lifestyle pills, (2) Leo's birth in 1908 and youth, (3) education, (4) in Vienna, (5) in Zurich, (6) at Hoffmann-La Roche, Basel, (7) to the New World, (8) at Roche, Nutley NJ, (9) invention of the new drugs, (10) revolution of people's lifestyle, and (11) reward, retirement and obituary in 2005. This paper may be the first comprehensive biography of this remarkable chemist written in Japanese.

  20. Low-Cost Propellant Launch to LEO from a Tethered Balloon - 'Propulsion Depots' Not 'Propellant Depots'

    NASA Technical Reports Server (NTRS)

    Wilcox, Brian H.; Schneider, Evan G.; Vaughan, David A.; Hall, Jeffrey L.; Yu, Chi Yau

    2011-01-01

    As we have previously reported, it may be possible to launch payloads into low-Earth orbit (LEO) at a per-kilogram cost that is one to two orders of magnitude lower than current launch systems, using only a relatively small capital investment (comparable to a single large present-day launch). An attractive payload would be large quantities of high-performance chemical rocket propellant (e.g. Liquid Oxygen/Liquid Hydrogen (LO2/LH2)) that would greatly facilitate, if not enable, extensive exploration of the moon, Mars, and beyond.

  1. Challenging Christianity: Leo Tolstoy and Religious Education

    ERIC Educational Resources Information Center

    Moulin, Dan

    2009-01-01

    The religious thought of Russian novelist Leo Tolstoy is a well documented but often overlooked example of unorthodox Christianity. This paper uses the example of Tolstoy's religious thinking to question the integrity of the current representation of Christianity in UK schools. It also uses Tolstoy's criticism of orthodox Christianity to suggest a…

  2. Leo Strauss: Education and the Body Politic

    ERIC Educational Resources Information Center

    Fennell, Jon M.; Simpson, Timothy L.

    2008-01-01

    Leo Strauss is commonly cited as a seminal influence for the neoconservatism that, in the minds of many commentators, dominates the administration of George W. Bush. What intersection, if any, exists between Strauss's views and neoconservatism? This paper investigates that question by studying Strauss's writings on liberal education and assessing…

  3. What Happened to Leo P's Metals?

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-12-01

    Measurements of metal abundances in galaxies present a conundrum: compared to expectations, there are not nearly enough metals observed within galaxies. New observations of a nearby dwarf galaxy may help us understand where this enriched material went.Removal ProcessesStar formation is responsible for the build-up of metals (elements heavier than helium) in a galaxy. But when we use a galaxys star-formation history to estimate the amount of enriched material it should contain, our predictions are inconsistent with measured abundances: large galaxies contain only about 2025% of the expected metals, and small dwarf galaxies contain as little as 1%!So what happens to galaxies metals after they have been formed? The favored explanation is that metals are removed from galaxies via stellar feedback: stars that explode in violent supernovae can drive high-speed winds, expelling the enriched material from a galaxy. This process should be more efficient in low-mass galaxies due to their smaller gravitational wells, which would explain why low-mass galaxies have especially low metallicities.But external processes may also contribute to the removal of metals, such as tidal stripping during interactions between galaxies. To determine the role of stellar feedback alone, an ideal test would be to observe an isolated low-mass, star-forming galaxy i.e., one that is not affected by external processes.Luckily, such an isolated, low-mass galaxy has recently been discovered just outside of the Local Group: Leo P, a gas-rich dwarf galaxy with a total stellar mass of 5.6 x 105 solar masses.Isolated ResultsPercentage of oxygen lost in Leo P compared to the percentage of metals lost in three other, similar-size dwarfs that are not isolated. If the gas-phase oxygen in Leo P were removed, Leo Ps measurements would be consistent with those of the other dwarfs. [McQuinn et al. 2015]Led by Kristen McQuinn (University of Minnesota, University of Texas at Austin), a team of researchers has used

  4. The IBEX-Lo Sensor

    NASA Astrophysics Data System (ADS)

    Fuselier, S. A.; Bochsler, P.; Chornay, D.; Clark, G.; Crew, G. B.; Dunn, G.; Ellis, S.; Friedmann, T.; Funsten, H. O.; Ghielmetti, A. G.; Googins, J.; Granoff, M. S.; Hamilton, J. W.; Hanley, J.; Heirtzler, D.; Hertzberg, E.; Isaac, D.; King, B.; Knauss, U.; Kucharek, H.; Kudirka, F.; Livi, S.; Lobell, J.; Longworth, S.; Mashburn, K.; McComas, D. J.; Möbius, E.; Moore, A. S.; Moore, T. E.; Nemanich, R. J.; Nolin, J.; O'Neal, M.; Piazza, D.; Peterson, L.; Pope, S. E.; Rosmarynowski, P.; Saul, L. A.; Scherrer, J. R.; Scheer, J. A.; Schlemm, C.; Schwadron, N. A.; Tillier, C.; Turco, S.; Tyler, J.; Vosbury, M.; Wieser, M.; Wurz, P.; Zaffke, S.

    2009-08-01

    The IBEX-Lo sensor covers the low-energy heliospheric neutral atom spectrum from 0.01 to 2 keV. It shares significant energy overlap and an overall design philosophy with the IBEX-Hi sensor. Both sensors are large geometric factor, single pixel cameras that maximize the relatively weak heliospheric neutral signal while effectively eliminating ion, electron, and UV background sources. The IBEX-Lo sensor is divided into four major subsystems. The entrance subsystem includes an annular collimator that collimates neutrals to approximately 7°×7° in three 90° sectors and approximately 3.5°×3.5° in the fourth 90° sector (called the high angular resolution sector). A fraction of the interstellar neutrals and heliospheric neutrals that pass through the collimator are converted to negative ions in the ENA to ion conversion subsystem. The neutrals are converted on a high yield, inert, diamond-like carbon conversion surface. Negative ions from the conversion surface are accelerated into an electrostatic analyzer (ESA), which sets the energy passband for the sensor. Finally, negative ions exit the ESA, are post-accelerated to 16 kV, and then are analyzed in a time-of-flight (TOF) mass spectrometer. This triple-coincidence, TOF subsystem effectively rejects random background while maintaining high detection efficiency for negative ions. Mass analysis distinguishes heliospheric hydrogen from interstellar helium and oxygen. In normal sensor operations, eight energy steps are sampled on a 2-spin per energy step cadence so that the full energy range is covered in 16 spacecraft spins. Each year in the spring and fall, the sensor is operated in a special interstellar oxygen and helium mode during part of the spacecraft spin. In the spring, this mode includes electrostatic shutoff of the low resolution (7°×7°) quadrants of the collimator so that the interstellar neutrals are detected with 3.5°×3.5° angular resolution. These high angular resolution data are combined with

  5. Shielded radiation protection quantities beyond LEO

    NASA Astrophysics Data System (ADS)

    Clowdsley, M. S.; Wilson, J. W.; Kim, M. Y.; Anderson, B. M.; Nealy, J. E.

    The National Council on Radiation Protection and Measurements (NCRP) has recommended that the quantities used to evaluate health risk to astronauts due to radiation exposure be effective dose and gray-equivalent. The NCRP recommends that effective dose be the limiting quantity for prevention of stochastic effects. Effective dose is a measure of whole body exposure, a weighted average of dose equivalent to a number body tissues for which the NCRP has adopted tissue weighting factors recommended by the International Commission on Radiation Protection (ICRP). For deterministic effects, the NCRP has recommended that gray-equivalent be used. Gray-equivalent is evaluated for specific critical organs and is the weighted sum of absorbed dose from field components to that organ using the relative biological effectiveness (RBE) number for that field component. RBE numbers recommended by the NCRP are used. The NCRP has provided effective dose limits as well as limits for gray-equivalent to eyes, skin, and blood forming organs (BFO) for astronauts in low earth orbit (LEO). As yet, no such limits have been defined for astronaut operations beyond LEO. In this study, the radiation protection quantities, effective dose and gray-equivalent to the eyes, skin, and BFO, are calculated for several environments beyond LEO. The lunar surface and Martian environments are included. For each environment, these radiation protection quantities are calculated behind varying amounts of various types of shielding materials. The results are compared to the exposure limits for LEO, since limits have not yet been defined for interplanetary missions. The benefits of using shielding material containing hydrogen and choosing optimal mission times are discussed.

  6. Leo satellite-based telecommunication network concepts

    NASA Technical Reports Server (NTRS)

    Aiken, John G.; Swan, Peter A.; Leopold, Ray J.

    1991-01-01

    Design considerations are discussed for Low Earth Orbit (LEO) satellite based telecommunications networks. The satellites are assumed to be connected to each other via intersatellite links. They are connected to the end user either directly or through gateways to other networks. Frequency reuse, circuit switching, packet switching, call handoff, and routing for these systems are discussed by analogy with terrestrial cellular (mobile radio) telecommunication systems.

  7. Nickel metal hydride LEO cycle testing

    NASA Technical Reports Server (NTRS)

    Lowery, Eric

    1995-01-01

    The George C. Marshall Space Flight Center is working to characterize aerospace AB5 Nickel Metal Hydride (NiMH) cells. The cells are being evaluated in terms of storage, low earth orbit (LEO) cycling, and response to parametric testing (high rate charge and discharge, charge retention, pulse current ability, etc.). Cells manufactured by Eagle Picher are the subjects of the evaluation. There is speculation that NiMH cells may become direct replacements for current Nickel Cadmium cells in the near future.

  8. Leo Satellite Communication through a LEO Constellation using TCP/IP Over ATM

    NASA Technical Reports Server (NTRS)

    Foore, Lawrence R.; Konangi, Vijay K.; Wallett, Thomas M.

    1999-01-01

    The simulated performance characteristics for communication between a terrestrial client and a Low Earth Orbit (LEO) satellite server are presented. The client and server nodes consist of a Transmission Control Protocol /Internet Protocol (TCP/IP) over ATM configuration. The ATM cells from the client or the server are transmitted to a gateway, packaged with some header information and transferred to a commercial LEO satellite constellation. These cells are then routed through the constellation to a gateway on the globe that allows the client/server communication to take place. Unspecified Bit Rate (UBR) is specified as the quality of service (QoS). Various data rates are considered.

  9. Instability of the Present LEO Satellite Populations

    NASA Technical Reports Server (NTRS)

    Liou, Jer-Chyi; Johnson, Nicholas L.

    2006-01-01

    Several studies conducted during 1991-2001 demonstrated, with some assumed launch rates, the future unintended growth potential of the Earth satellite population, resulting from random, accidental collisions among resident space objects. In some low Earth orbit (LEO) altitude regimes where the number density of satellites is above a critical spatial density, the production rate of new breakup debris due to collisions would exceed the loss of objects due to orbital decay. A new study has been conducted in the Orbital Debris Program Office at the NASA Lyndon B. Johnson Space Center, using higher fidelity models to evaluate the current debris environment. The study assumed no satellites were launched after December 2005. A total of 150 Monte Carlo runs were carried out and analyzed. Each Monte Carlo run simulated the current debris environment and projected it 200 years into the future. The results indicate that the LEO debris environment has reached a point such that even if no further space launches were conducted, the Earth satellite population would remain relatively constant for only the next 50 years or so. Beyond that, the debris population would begin to increase noticeably, due to the production of collisional debris. Detailed analysis shows that this growth is primarily driven by high collision activities around 900 to 1000 km altitude - the region which has a very high concentration of debris at present. In reality, the satellite population growth in LEO will undoubtedly be worse than this study indicates, since spacecraft and their orbital stages will continue to be launched into space. Postmission disposal of vehicles (e.g., limiting postmission orbital lifetimes to less than 25 years) will help, but will be insufficient to constrain the Earth satellite population. To preserve better the near-Earth environment for future space activities, it might be necessary to remove existing large and massive objects from regions where high collision activities are

  10. CDDIS Support of IGS LEO Activities

    NASA Technical Reports Server (NTRS)

    Noll, Carey E.; Smith, David E. (Technical Monitor)

    2001-01-01

    The Crustal Dynamics Data Information System (CDDIS) has served as a global data center for the International GPS Service (IGS) since its start in June 1992, providing on-line access to data from over 175 sites on a daily and hourly basis. This paper will present an overview about the current status of the CDDIS GPS data and products archive with a look to the future support of LEO (Low Earth Orbiting missions), including the archive of high-rate data and on-board GPS receiver data.

  11. Effects of LEO Environment on Tensile Properties of PEEK Films

    NASA Astrophysics Data System (ADS)

    Nakamura, Takashi; Nakamura, Hiroshi; Shimamura, Hiroyuki

    2009-01-01

    To clarify the effects of space environment on mechanical properties of polymer, exposure experiments were conducted utilizing the International Space Station Russian Service Module. Poly-ether-ether-ketone (PEEK) films under tensile stress were exposed to low Earth orbit (LEO) environment, and reference samples were irradiated with atomic oxygen (AO), electron beam (EB), and ultraviolet light (UV) in ground facilities. By comparing the results of flight and ground tests, the degradation behavior and the influential factors in LEO were investigated. The following results were obtained. (1) UV was found to be the harshest factor in LEO on tensile properties, since it decreased elongation to 15% of pristine sample after 46-months exposure. (2) AO in LEO eroded the specimen surface with a cone-like morphology and reduced the thickness; however, it had no significant effect on tensile properties. (3) EB irradiation in LEO had no measurable effects on the material properties.

  12. Individual Pressure Vessel (PV) and Common Pressure Vessel (CPV) Nickel-Hydrogen Battery Performance Under LEO Cycling Conditions

    NASA Technical Reports Server (NTRS)

    Miller, Thomas B.; Lewis, Harlan L.

    2004-01-01

    LEO life cycle testing of Individual Pressure Vessel (PV) and Common Pressure Vessel (CPV) nickel-hydrogen cell packs have been sponsored by the NASA Aerospace Flight Battery Program. The cell packs have cycled under both 35% and 60% depth-of- discharge and temperature conditions of -5 C and +lO C. The packs have been on test since as early as 1992 and have generated a substantial database. This report will provide insight into performance trends as a function of the specific cell configuration and manufacturer for eight separate nickel-hydrogen battery cell packs.

  13. POSSIBLE CHROMOSPHERIC ACTIVITY CYCLES IN AD LEO

    SciTech Connect

    Buccino, Andrea P.; Petrucci, Romina; Mauas, Pablo J. D.; Jofré, Emiliano

    2014-01-20

    AD Leo (GJ 388) is an active dM3 flare star that has been extensively observed both in the quiescent and flaring states. Since this active star is near the fully convective boundary, studying its long-term chromospheric activity in detail could be an appreciable contribution to dynamo theory. Here, using the Lomb-Scargle periodogram, we analyze the Ca II K line-core fluxes derived from CASLEO spectra obtained between 2001 and 2013 and the V magnitude from the ASAS database between 2004 and 2010. From both of these totally independent time series, we obtain a possible activity cycle with a period of approximately seven years and a less significant shorter cycle of approximately two years. A tentative interpretation is that a dynamo operating near the surface could be generating the longer cycle, while a second dynamo operating in the deep convection zone could be responsible for the shorter one. Based on the long duration of our observing program at CASLEO and the fact that we observe different spectral features simultaneously, we also analyze the relation between simultaneous measurements of the Na I index (R{sub D}{sup ′}), Hα, and Ca II K fluxes at different activity levels of AD Leo, including flares.

  14. AH Leo and the Blazhko Effect

    NASA Astrophysics Data System (ADS)

    Phillips, J.; Gay, P. L.

    2004-12-01

    We obtained 563 V-Band observations of AH Leo between January 27 and May 12, 2004. All observations were obtained with a 12-inch Schmidt-Cassegrain located on the island of Saipan, in the Commonwealth of the Northern Mariana Islands. We show that AH Leo is a type RRab RR Lyrae star with a minimum magnitude of V=14.658 magnitudes, a maximum amplitude of 0.989 magnitudes and a minimum amplitude of perhaps just 0.4 magnitudes. Its primary period is 0.4662609 days. Our observations also confirm the presence of the Blazhko effect, which had previously been detected by Smith and Gay (private communication) in 1993 and 1994. We estimate the Blazhko period to be roughly 20-days, however poor phase coverage at maximum light makes exact determination impossible. We also note that the bump during minimum, which is common in many RR Lyraes, varied throughout the Blazhko cycle, demonstrating amplitudes between 0 and 0.15 magnitudes. We would like to thank Sarah Maddison and Swinburne Astronomy Online for supporting this project

  15. EVLA Observations of the Leo Ring

    NASA Astrophysics Data System (ADS)

    Kent, Brian R.; Chung, A.; Wrobel, J. M.; Ott, J.; Morrison, G. E.; Bekki, K.; Park, H.

    2012-01-01

    We present new EVLA D-configuration data of the Leo Ring. The 21cm observations show high spatial and spectral resolution maps of the ring in neutral hydrogen. The region associated with the ring is located at a distance of 10 Mpc, and consists of an intermediate density group of galaxies when compared with the denser Virgo Cluster to the east. Whereas single-dish observations are sensitive to large-scale diffuse features, the interferometric data are sensitive to the population of small dwarf galaxies (˜ 0.08 Jy km/s and 20 km/s). The nine field mosaic (covering the 200 kpc diameter HI ring) consists of 8 hours per field with a 4 MHz bandwidth (covering over 800 km/s in cz space) on the new EVLA WIDAR correlator allowing for coverage of all the spectral features of the ring and galaxy group. The correlator setup gives a 1.953 kHz channel spacing (˜ 0.5 km/s at the HI line). The synthesized beam for this configuration is ˜ 45" (2.2 kpc at the Leo distance). The data allow us to constrain models for the origin of the HI ring (primordial vs. stripped) and to search for dwarfs in the ring to a limiting HI mass of ˜ 106 M⊙. We report on preliminary HI results and compare with the CFHT mosaic images from the literature.

  16. 20 CFR 10.737 - How is a LEO claim filed, and who can file a LEO claim?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false How is a LEO claim filed, and who can file a LEO claim? 10.737 Section 10.737 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS...' COMPENSATION ACT, AS AMENDED Special Provisions Non-Federal Law Enforcement Officers § 10.737 How is a...

  17. Light Pollution in Leo-Satellite Tracking

    NASA Astrophysics Data System (ADS)

    Shakun, L. S.; Marsakova, V. I.; Golubovskaya, T. A.; Terpan, S. S.; Melikyants, S. M.; Korobeynikova, E. A.

    Because of the high level of the light pollution in Odessa city, only the observations of LEO (low Earth orbit)-satellites are performed in the main office of the Astronomical observatory of Odessa National University named after I.I. Mechnikov. As the one of the observation results we obtain the sky background measurements along the satellite's way through the sky (at different azimuths and altitudes that change during the satellite tracking). We propose the method of irregular extinction changes diagnostics that realized by using the different data filtration methods. Also as the result of our analysis of these observations we present azimuth-altitude diagram of sky background that shows the most significant light pollution at the north-western and northern directions caused by the Port of Odessa and the stadium "Chernomorets".

  18. Demonstration of Uncued Optical Surveillance of LEO

    NASA Astrophysics Data System (ADS)

    Zimmer, P.; Ackermann, M.; McGraw, J.

    2014-09-01

    J.T. McGraw and Associates, LLC, in collaboration with the University of New Mexico (UNM), has built and is operating two proof-of-concept wide-field imaging systems to test novel techniques for uncued surveillance of LEO. The imaging systems are built from off-the-shelf optics and detectors resulting in a 350mm aperture and a 6 square degree field of view. For streak detection, field of view is of critical importance because the maximum exposure time on the object is limited by its crossing time and measurements of apparent angular motion are better constrained with longer streaks. The current match of the detector to the optical system is optimized for detection of objects at altitudes above 450km, which for a circular orbit, corresponds to apparent motions of approximately 1 deg./sec. Using our GPU-accelerated detection scheme, the proof-of-concept systems have detected objects fainter than V=12.3, which approximately corresponds to a 24 cm object at 1000 km altitude at better than 6 sigma significance, from sites near and within Albuquerque, NM. This work demonstrates scalable optical systems designed for near real time detection of fast moving objects, which can be then handed off to other instruments capable of tracking and characterizing them. The two proof-of-concept systems, separated by ~30km, work together by taking simultaneous images of the same orbital volume to constrain the orbits of detected objects using parallax measurements. These detections are followed-up by photometric observations taken at UNM to independently assess the objects and the quality of the derived orbits. We believe this demonstrates the potential of small telescope arrays for detecting and cataloguing heretofore unknown LEO objects.

  19. LoWMob: Intra-PAN Mobility Support Schemes for 6LoWPAN.

    PubMed

    Bag, Gargi; Raza, Muhammad Taqi; Kim, Ki-Hyung; Yoo, Seung-Wha

    2009-01-01

    Mobility in 6LoWPAN (IPv6 over Low Power Personal Area Networks) is being utilized in realizing many applications where sensor nodes, while moving, sense and transmit the gathered data to a monitoring server. By employing IEEE802.15.4 as a baseline for the link layer technology, 6LoWPAN implies low data rate and low power consumption with periodic sleep and wakeups for sensor nodes, without requiring them to incorporate complex hardware. Also enabling sensor nodes with IPv6 ensures that the sensor data can be accessed anytime and anywhere from the world. Several existing mobility-related schemes like HMIPv6, MIPv6, HAWAII, and Cellular IP require active participation of mobile nodes in the mobility signaling, thus leading to the mobility-related changes in the protocol stack of mobile nodes. In this paper, we present LoWMob, which is a network-based mobility scheme for mobile 6LoWPAN nodes in which the mobility of 6LoWPAN nodes is handled at the network-side. LoWMob ensures multi-hop communication between gateways and mobile nodes with the help of the static nodes within a 6LoWPAN. In order to reduce the signaling overhead of static nodes for supporting mobile nodes, LoWMob proposes a mobility support packet format at the adaptation layer of 6LoWPAN. Also we present a distributed version of LoWMob, named as DLoWMob (or Distributed LoWMob), which employs Mobility Support Points (MSPs) to distribute the traffic concentration at the gateways and to optimize the multi-hop routing path between source and destination nodes in a 6LoWPAN. Moreover, we have also discussed the security considerations for our proposed mobility schemes. The performance of our proposed schemes is evaluated in terms of mobility signaling costs, end-to-end delay, and packet success ratio.

  20. LoWMob: Intra-PAN Mobility Support Schemes for 6LoWPAN.

    PubMed

    Bag, Gargi; Raza, Muhammad Taqi; Kim, Ki-Hyung; Yoo, Seung-Wha

    2009-01-01

    Mobility in 6LoWPAN (IPv6 over Low Power Personal Area Networks) is being utilized in realizing many applications where sensor nodes, while moving, sense and transmit the gathered data to a monitoring server. By employing IEEE802.15.4 as a baseline for the link layer technology, 6LoWPAN implies low data rate and low power consumption with periodic sleep and wakeups for sensor nodes, without requiring them to incorporate complex hardware. Also enabling sensor nodes with IPv6 ensures that the sensor data can be accessed anytime and anywhere from the world. Several existing mobility-related schemes like HMIPv6, MIPv6, HAWAII, and Cellular IP require active participation of mobile nodes in the mobility signaling, thus leading to the mobility-related changes in the protocol stack of mobile nodes. In this paper, we present LoWMob, which is a network-based mobility scheme for mobile 6LoWPAN nodes in which the mobility of 6LoWPAN nodes is handled at the network-side. LoWMob ensures multi-hop communication between gateways and mobile nodes with the help of the static nodes within a 6LoWPAN. In order to reduce the signaling overhead of static nodes for supporting mobile nodes, LoWMob proposes a mobility support packet format at the adaptation layer of 6LoWPAN. Also we present a distributed version of LoWMob, named as DLoWMob (or Distributed LoWMob), which employs Mobility Support Points (MSPs) to distribute the traffic concentration at the gateways and to optimize the multi-hop routing path between source and destination nodes in a 6LoWPAN. Moreover, we have also discussed the security considerations for our proposed mobility schemes. The performance of our proposed schemes is evaluated in terms of mobility signaling costs, end-to-end delay, and packet success ratio. PMID:22346730

  1. LoWMob: Intra-PAN Mobility Support Schemes for 6LoWPAN

    PubMed Central

    Bag, Gargi; Raza, Muhammad Taqi; Kim, Ki-Hyung; Yoo, Seung-Wha

    2009-01-01

    Mobility in 6LoWPAN (IPv6 over Low Power Personal Area Networks) is being utilized in realizing many applications where sensor nodes, while moving, sense and transmit the gathered data to a monitoring server. By employing IEEE802.15.4 as a baseline for the link layer technology, 6LoWPAN implies low data rate and low power consumption with periodic sleep and wakeups for sensor nodes, without requiring them to incorporate complex hardware. Also enabling sensor nodes with IPv6 ensures that the sensor data can be accessed anytime and anywhere from the world. Several existing mobility-related schemes like HMIPv6, MIPv6, HAWAII, and Cellular IP require active participation of mobile nodes in the mobility signaling, thus leading to the mobility-related changes in the protocol stack of mobile nodes. In this paper, we present LoWMob, which is a network-based mobility scheme for mobile 6LoWPAN nodes in which the mobility of 6LoWPAN nodes is handled at the network-side. LoWMob ensures multi-hop communication between gateways and mobile nodes with the help of the static nodes within a 6LoWPAN. In order to reduce the signaling overhead of static nodes for supporting mobile nodes, LoWMob proposes a mobility support packet format at the adaptation layer of 6LoWPAN. Also we present a distributed version of LoWMob, named as DLoWMob (or Distributed LoWMob), which employs Mobility Support Points (MSPs) to distribute the traffic concentration at the gateways and to optimize the multi-hop routing path between source and destination nodes in a 6LoWPAN. Moreover, we have also discussed the security considerations for our proposed mobility schemes. The performance of our proposed schemes is evaluated in terms of mobility signaling costs, end-to-end delay, and packet success ratio. PMID:22346730

  2. LEO P: AN UNQUENCHED VERY LOW-MASS GALAXY

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Berg, Danielle; Dolphin, Andrew; Cannon, John M.; Salzer, John J.; Rhode, Katherine L.; Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P.; Girardi, Léo

    2015-10-20

    Leo P is a low-luminosity dwarf galaxy discovered through the blind H i Arecibo Legacy Fast ALFA survey. The H i and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62 ± 0.15 Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ∼0.4 Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the H ii region is most likely an O7V or O8V spectral type, with a stellar mass ≳25 M{sub ⊙}. The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ∼10{sup −5} M{sub ⊙} yr{sup −1}. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a low-mass dSph would look like if it evolved in isolation and retained its gas. Despite the very low mass of Leo P, the imprint of reionization on its SFH is subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites.

  3. Leo P: An Unquenched Very Low-mass Galaxy

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dolphin, Andrew; Cannon, John M.; Salzer, John J.; Rhode, Katherine L.; Adams, Elizabeth A. K.; Berg, Danielle; Giovanelli, Riccardo; Girardi, Léo; Haynes, Martha P.

    2015-10-01

    Leo P is a low-luminosity dwarf galaxy discovered through the blind H i Arecibo Legacy Fast ALFA survey. The H i and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62 ± 0.15 Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ˜0.4 Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the H ii region is most likely an O7V or O8V spectral type, with a stellar mass ≳25 M⊙. The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ˜10-5 M⊙ yr-1. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a low-mass dSph would look like if it evolved in isolation and retained its gas. Despite the very low mass of Leo P, the imprint of reionization on its SFH is subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites. Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained from the

  4. LoTi Turns Up the Heat!

    ERIC Educational Resources Information Center

    Moersch, Christopher

    2010-01-01

    When LoTi was first introduced in 1994 as the Levels of Technology Implementation framework, the intent was to create a tool to help district leadership quantify how teachers were using technology in the classroom. After serving the past 15 years as a research framework, self-reporting technology integration survey, and school improvement model,…

  5. Leo Szilard In Physics and Information

    NASA Astrophysics Data System (ADS)

    Garwin, Richard

    2014-03-01

    The excellent biography by William Lanouette, ``Genius in the Shadows,'' tells it the way it was, incredible though it may seem. The 1972 ``Collected Works of Leo Szilard: Scientific Papers'' Bernard T. Feld and Getrude W. Szilard, Editors, gives the source material both published and unpublished. Szilard's path-breaking but initially little-noticed 1929 paper, ``On the Decrease of Entropy in a Thermodynamic System by the Intervention of Intelligent Beings'' spawned much subsequent research. It connected what we now call a bit of information with a quantity k ln 2 of entropy, and showed that the process of acquiring, exploiting, and resetting this information in a one-molecule engine must dissipate at least kT ln 2 of energy at temperature T. His 1925 paper, ``On the Extension of Phenomenological Thermodynamics to Fluctuation Phenomena,'' showed that fluctuations were consistent with and predicted from equilibrium thermodynamics and did not depend on atomistic theories. His work on physics and technology, demonstrated an astonishing range of interest, ingenuity, foresight, and practical sense. I illustrate this with several of his fundamental contributions nuclear physics, to the neutron chain reaction and to nuclear reactors, and also to electromagnetic pumping of liquid metals.

  6. TT and C - First TDRSS, Then Commercial GEO and Big LEO and Now through LEO

    NASA Technical Reports Server (NTRS)

    Morgan, Dwayne; Bull, Barton; Grant, Charles; Streich, Ronald; Powers, Edward I. (Technical Monitor)

    2001-01-01

    The advent of low earth orbit (LEO) commercial communications satellites provides an opportunity to dramatically reduce Telemetry Tracking and Control (TT&C) costs of launch vehicles and Unpiloted Aerial Vehicles (UAVs) by reducing or eliminating ground infrastructure. Personnel from the Goddard Space Flight Center Wallops Flight Facility (GSFC/WFF) in Virginia have successfully used commercial GEO & Big LEO communications satellites for Long Duration Balloon flight TT&C. In addition, TDRSS capability for these balloons has been developed by WFF for the Ultra Long Duration Balloons with the first test flight launch in January 2001 for one global circumnavigation at 120,000 feet altitude launched from Alice Springs. Australia. Numerous other low cost applications can new utilize the commercial LEO satellites for TT&C. The Flight Modern became a GSFC/WFF Advanced Range Technology Initiative (ARTI) in an effort to streamline TT&C capability to the user community at low cost. Phase I ground tests of The Flight Modem verified downlink communications quality of service and measured transmission latencies. These tests were completed last year, Phase II consisting of aircraft flight tests provide much of the data presented in this paper. Phase III of the Flight Modern baseline test program is a demonstration of the ruggedized version of the WFF Flight Modem flown on one sounding rocket launched from Sweden. Flights of opportunity have been and are being actively pursued with other centers, ranges and users at universities. The WFF goal is to reduce TT&C costs by providing a low cost COTS Flight Modem with a User Handbook containing system capability and limitation descriptions. Additionally, since data transmission is by packetized Internet Protocol (IP), data can be received and commands initialed from practically any location with no infrastructure. The WFF, like most ranges, has been using GPS receivers on sounding rockets and long duration balloons for several years

  7. PECULIAR VELOCITIES OF GALAXIES IN THE LEO SPUR

    SciTech Connect

    Karachentsev, Igor D.; Makarova, Lidia N.; Makarov, Dmitry I.; Tully, R. Brent; Rizzi, Luca

    2015-06-01

    The Hubble Space Telescope Advanced Camera for Surveys has been used to determine accurate distances for the spiral galaxy NGC 2683 and 12 other galaxies in a zone of the “local velocity anomaly” from luminosity measurements of the brightest red giant branch stars. These galaxies lie in the Leo Spur, the nearest filament beyond our Local Sheet. The new accurate distance measurements confirm that galaxies along the Leo Spur are more distant than expected from uniform cosmic expansion, and hence have large and peculiar velocities toward us. The motions are generally explained by a previously published model that posits that the Local Sheet is descending at 259 km s{sup −1} toward the south supergalactic pole due to expansion of the Local Void and is being attracted toward the Virgo Cluster at 185 km s{sup −1}. With the standard ΛCDM cosmology, an empty void expands at 16 km s{sup −1} Mpc{sup −1}, so a motion of 259 km s{sup −1} requires the Local Void to be impressively large and empty. Small residuals from the published model can be attributed to an upward push toward the north supergalactic pole by the expansion of the Gemini–Leo Void below the Leo Spur. The Leo Spur is sparsely populated, but among its constituents there are two associations that contain only dwarf galaxies.

  8. System using leo satellites for centimeter-level navigation

    NASA Technical Reports Server (NTRS)

    Rabinowitz, Matthew (Inventor); Parkinson, Bradford W. (Inventor); Cohen, Clark E. (Inventor); Lawrence, David G. (Inventor)

    2002-01-01

    Disclosed herein is a system for rapidly resolving position with centimeter-level accuracy for a mobile or stationary receiver [4]. This is achieved by estimating a set of parameters that are related to the integer cycle ambiguities which arise in tracking the carrier phase of satellite downlinks [5,6]. In the preferred embodiment, the technique involves a navigation receiver [4] simultaneously tracking transmissions [6] from Low Earth Orbit Satellites (LEOS) [2] together with transmissions [5] from GPS navigation satellites [1]. The rapid change in the line-of-sight vectors from the receiver [4] to the LEO signal sources [2], due to the orbital motion of the LEOS, enables the resolution with integrity of the integer cycle ambiguities of the GPS signals [5] as well as parameters related to the integer cycle ambiguity on the LEOS signals [6]. These parameters, once identified, enable real-time centimeter-level positioning of the receiver [4]. In order to achieve high-precision position estimates without the use of specialized electronics such as atomic clocks, the technique accounts for instabilities in the crystal oscillators driving the satellite transmitters, as well as those in the reference [3] and user [4] receivers. In addition, the algorithm accommodates as well as to LEOS that receive signals from ground-based transmitters, then re-transmit frequency-converted signals to the ground.

  9. A Novel Spacecraft Charge Monitor for LEO

    NASA Technical Reports Server (NTRS)

    Goembel, Luke

    2004-01-01

    Five years ago we introduced a new method for measuring spacecraft chassis floating potential relative to the space plasma (absolute spacecraft potential) in low Earth orbit. The method, based on a straightforward interpretation of photoelectron spectra, shows promise for numerous applications, but has not yet been tried. In the interest of testing the method, and ultimately supplying another tool for measuring absolute spacecraft charge, we are producing a flight prototype Spacecraft Charge Monitor (SCM) with support from NASA's Small Business Innovation Research (SBIR) program. Although insight into the technique came from data collected in space over two decades ago, very little data are available. The data indicate that it may be possible to determine spacecraft floating potential to within 0.1 volt each with the SCM second under certain conditions. It is debatable that spacecraft floating potential has ever been measured with such accuracy. The compact, easily deployed SCM also offers the advantage of long-term stability in calibration. Accurate floating potential determinations from the SCM could be used to correct biases in space plasma measurements and evaluate charge mitigation and/or sensing devices. Although this paper focuses on the device's use in low Earth orbit (LEO), the device may also be able to measure spacecraft charge at higher altitudes, in the solar wind, and in orbits around other planets. The flight prototype SCM we are producing for delivery to NASA in the third quarter of 2004 will measure floating potential from 0 to -150 volts with 0.1 volt precision, weigh approximately 600-700 grams, consume approximately 2 watts, and will measure approximately 8 x 10 x 17 cm.

  10. PRECISION POINTING OF IBEX-Lo OBSERVATIONS

    SciTech Connect

    Hlond, M.; Bzowski, M.; Moebius, E.; Kucharek, H.; Heirtzler, D.; Schwadron, N. A.; Neill, M. E. O'; Clark, G.; Crew, G. B.; Fuselier, S.; McComas, D. J. E-mail: eberhard.moebius@unh.edu E-mail: stephen.a.fuselier@linco.com E-mail: DMcComas@swri.edu

    2012-02-01

    Post-launch boresight of the IBEX-Lo instrument on board the Interstellar Boundary Explorer (IBEX) is determined based on IBEX-Lo Star Sensor observations. Accurate information on the boresight of the neutral gas camera is essential for precise determination of interstellar gas flow parameters. Utilizing spin-phase information from the spacecraft attitude control system (ACS), positions of stars observed by the Star Sensor during two years of IBEX measurements were analyzed and compared with positions obtained from a star catalog. No statistically significant differences were observed beyond those expected from the pre-launch uncertainty in the Star Sensor mounting. Based on the star observations and their positions in the spacecraft reference system, pointing of the IBEX satellite spin axis was determined and compared with the pointing obtained from the ACS. Again, no statistically significant deviations were observed. We conclude that no systematic correction for boresight geometry is needed in the analysis of IBEX-Lo observations to determine neutral interstellar gas flow properties. A stack-up of uncertainties in attitude knowledge shows that the instantaneous IBEX-Lo pointing is determined to within {approx}0.{sup 0}1 in both spin angle and elevation using either the Star Sensor or the ACS. Further, the Star Sensor can be used to independently determine the spacecraft spin axis. Thus, Star Sensor data can be used reliably to correct the spin phase when the Star Tracker (used by the ACS) is disabled by bright objects in its field of view. The Star Sensor can also determine the spin axis during most orbits and thus provides redundancy for the Star Tracker.

  11. Ambient noise tomography of Lo'ihi

    NASA Astrophysics Data System (ADS)

    McClement, K.; Thurber, C. H.; Teel, A.; Caplan-Auerbach, J.

    2012-12-01

    Lo'ihi seamount, the youngest volcano in the Hawaiian-Emperor chain, lies approximately 30 km south of Hawai'i Island with its summit still approximately 1 km below sea level. Lo'ihi offers a unique opportunity to study the early formation of a hotspot volcano and can provide insight into the deep internal structure of the other volcanoes that make up the Hawaiian Islands. This study uses Ambient Noise Tomography (ANT) to create a 3D tomographic image of Lo'ihi's S-wave velocity structure from ocean bottom seismometer (OBS) data. ANT has been used in many subaerial studies but has seen very few applications to OBS data. This study uses continuous data recorded in 2010 to 2011 from 12 short-period OBS instruments deployed on and around Lo'ihi. With the farthest distance between stations being just over 30 km, the stations provide a fairly dense coverage mainly for the northern half of the volcano. Following the approach of Masterlark et al. [2010], we computed vertical-vertical and vertical-radial cross-correlations using 97 days of continuous data from the 12 stations to produce the ambient noise Green's functions. From these, dispersion curves were produced over a frequency range from .04 Hz to 0.65 Hz . After a quality control analysis, checkerboard tests were used to determine a suitable cell size for the 2D group velocity inversions. The final step is the inversion of the group velocity dispersion curves to create a 3D Vs model. The 3D Vs image produced through this method does not provide clear evidence of a shallow magma chamber; however, when compared to a previous P-wave velocity (Vp) model [Caplan-Auerbach, 2001], a high Vp/Vs ratio is evident especially at depths from 1 km to 5 km, indicating the presence of highly fractured rock.

  12. An Update on the Effectiveness of Postmission Disposal in LEO

    NASA Technical Reports Server (NTRS)

    Liou, J.-C; Krisko, Paula

    2013-01-01

    Orbital debris mitigation measures have been developed to reduce the growth of the future debris population by the international space community over the past two decades. A major component in the overall mitigation strategy is postmission disposal (PMD). A key PMD element for the low Earth orbit (LEO, the region below 2000 km altitude) satellites is the 25-year decay rule. It is intended to limit the long-term presence of massive intact objects - rocket bodies (R/Bs) and spacecraft (S/C) in the environment. The effectiveness of the 25-year rule was well demonstrated and documented during the development of the mitigation measures. The orbital debris population in LEO, unfortunately, has significantly increased since that time. The objectives of this paper are to provide an updated assessment based on the 2012 LEO environment and to highlight the importance of the global compliance of the 25-year decay rule.

  13. Variable stars in the Leo A dwarf galaxy (DDO 69)

    NASA Technical Reports Server (NTRS)

    Hoessel, John G.; Saha, A.; Krist, John; Danielson, G. Edward

    1994-01-01

    Observations of the Leo A dwarf galaxy, obtained over the period from 1980 to 1991 are reported. Forty two separate Charge Coupled Devices (CCD) frames were searched for variable stars. A total of 14 suspected variables were found, 9 had sufficient coverage for period determination, and 5 had Cepheid light curves. Four of these stars fit well on a P-L relation and yield a distance modulus, after correction for Galactic foreground extinction, of m-M = 26.74. This corresponds to a distance of 2.2 Mpc, placing Leo A near the Local Group zero-velocity surface.

  14. Leo I - The youngest Milky Way dwarf spheroidal galaxy?

    NASA Technical Reports Server (NTRS)

    Lee, Myung G.; Freedman, Wendy; Mateo, Mario; Thompson, Ian; Roth, Miguel; Ruiz, Maria-Teresa

    1993-01-01

    Deep CCD photometry of about 16,000 stars in the Milky Way's Leo I spheroidal galaxy satellite is reported. An account is given of the features observed in the color-magnitude diagrams (CMDs) derived therefrom. A very blue and well-defined red giant branch (RGB) is noted. The CMDs of Leo I shows about 50 anomalous Cepheid candidates; there are another 50 or so asymptotic giant branch stars above the tip of the RGB, including 15 known carbon stars. The mean color of the RGB is estimated at M sub I = -3.5 mag.

  15. Solar Array Arcing in LEO How Much Charge is Discharged?

    NASA Technical Reports Server (NTRS)

    Ferguson, D. C.; Vayner, B. V.; Galofaro, J. T.

    2004-01-01

    It is often said that only the solar array or spacecraft surface that can be reached by an arc plume are discharged in a solar array arc in LEO (Low Earth Orbit). We present definitive results from ground test experiments done in the National Plasma Interactions (N-PI) facility at the NASA Glenn Research Center that this idea is mistaken. All structure surfaces in contact with the surrounding plasma and connected to spacecraft ground are discharged, whether the arc plasma can reach them or not. Implications from the strength and damaging effects of areas on LEO spacecraft are discussed, and mitigation techniques are proposed.

  16. Lo Gnomone Clementino Astronomia Meridiana in Basilica

    NASA Astrophysics Data System (ADS)

    Sigismondi, Costantino

    2014-05-01

    Costruito per chiara volontà del papa 70 anni dopo il caso Galileo, lo Gnomone Clementino è un grande telescopio solare che non fa uso di lenti a 92 anni dall’invenzione del cannocchiale. Queste due caratteristiche basterebbero da sole a giustificare l’interesse verso questo strumento. L’astronomia meridiana è alla base dell’astrometria e dell’astrofisica moderna. Lo Gnomone Clementino sta oggi all’astronomia, come il veliero “Amerigo Vespucci” sta alla Marina Italiana. E’ possibile svolgere ogni genere di osservazione e studio su questo strumento, e dal 2002 vi tengo lezioni teorico-pratiche del corso di Storia dell’Astronomia e La Terra nel Sistema Solare della Sapienza, Università di Roma, Facoltà di Lettere e Filosofia. Questo testo aggiunge alcuni tasselli alla ricerca storica sulla meridiana, appoggiandosi, com’è naturale, sulle spalle di giganti che mi hanno preceduto in questi studi. In particolare la misura dell’azimut della meridiana, ed il suo inquadramento tra gli strumenti simili ed alcuni studi di astrometria sui dati del 1701-1703 di Bianchini, che sono apparsi fin’ora soltanto su riviste specializzate ed in Inglese vengono qui proposti in Italiano e semplificati, per valorizzare sempre più questa straordinaria opera d’arte e di scienza.

  17. Complete mitochondrial genome of a Asian lion (Panthera leo goojratensis).

    PubMed

    Li, Yu-Fei; Wang, Qiang; Zhao, Jian-ning

    2016-01-01

    The entire mitochondrial genome of this Asian lion (Panthera leo goojratensis) was 17,183 bp in length, gene composition and arrangement conformed to other lions, which contained the typical structure of 22 tRNAs, 2 rRNAs, 13 protein-coding genes and a non-coding region. The characteristic of the mitochondrial genome was analyzed in detail.

  18. Leo Esaki: An Outsider Brings a Culture Change to Tsukuba.

    ERIC Educational Resources Information Center

    Normile, Dennis

    1994-01-01

    Describes a wave of reforms set in motion by Nobel laureate Leo Esaki, to encourage industry to play a bigger role in graduate education through a new program that enables doctoral candidates to work in 31 participating corporate and government labs near the University of Tsukuba, Japan. (LZ)

  19. Sowing the Seeds of the Autism Field: Leo Kanner (1943)

    ERIC Educational Resources Information Center

    Blacher, Jan; Christensen, Lisa

    2011-01-01

    More than 65 years after Leo Kanner published his seminal article, research on autism continues to be an area of increasing interest. Although much progress has been made, this field is still in its infancy, and many avenues of research are just beginning to be pursued. Despite the time that has passed, the syndrome Kanner identified and his…

  20. Satellite Telemetry and Command using Big LEO Mobile Telecommunications Systems

    NASA Technical Reports Server (NTRS)

    Huegel, Fred

    1998-01-01

    Various issues associated with satellite telemetry and command using Big LEO mobile telecommunications systems are presented in viewgraph form. Specific topics include: 1) Commercial Satellite system overviews: Globalstar, ICO, and Iridium; 2) System capabilities and cost reduction; 3) Satellite constellations and contact limitations; 4) Capabilities of Globalstar, ICO and Iridium with emphasis on Globalstar; and 5) Flight transceiver issues and security.

  1. Saint Leo University: A Values-Based Education

    ERIC Educational Resources Information Center

    Carter, Beth H.

    2009-01-01

    Saint Leo University is committed to integrating values in its curriculum and activities; however, there is little information available to determine if it is meeting its goals. The institution offers both a traditional program and nontraditional accelerated program. Therefore, it is important for the institution to determine if it is instilling…

  2. Neoconservatism and Leo Strauss: The Place of a Liberal Education

    ERIC Educational Resources Information Center

    York, J. G.

    2008-01-01

    This paper is concerned with the work of Leo Strauss, specifically his two essays on liberal education. Strauss is often claimed to be a founding thinker of neoconservatism and while much scholarship has been produced analyzing his work, very little discusses his essays on liberal education and how these fit within his larger project. This essay…

  3. Exploiting link dynamics in LEO-to-ground communications

    SciTech Connect

    Palmer, Joseph Mcrae; Caffrey, Michael P

    2009-01-01

    The high dynamics of the LEO-to-ground radio channel are described. An analysis shows how current satellite radio systems largely underutilize the available radio link, and that a radio that can adaptively vary the bit rate can more fully exploit it, resulting in increased data throughput and improved power efficiency. We propose one method for implementing the adaptivity, and present simulation results.

  4. Radiation field formation and monitoring beyond LEO

    NASA Astrophysics Data System (ADS)

    Miroshnichenko, L. I.

    This brief review comprises the main features of radiation field formation due to galactic (GCR) and solar cosmic rays (SCR) beyond LEO in the inner Solar system. We also consider the similarities and differences of radiation environment models applicable to the Moon and the Mars missions, the main requirements for radiation monitoring, warning and forecasting techniques for deep space missions. Existing modulation models for GCR provide a possibility to estimate easily the GCR contribution to the radiation field in the interplanetary space, at the lunar or Martian surfaces; the situation with SCR contribution is much more complicated. For space weather purposes, time profiles of the 10-30 MeV protons, unfortunately, are often complicated by several factors, especially by interplanetary shocks driven by Coronal Mass Ejections (CME). In particular, the particle-trapping region around the shock may or may not be the region with the highest SEP intensity, depending on whether shock acceleration continues or diminishes with distance. At distances beyond 1 AU there can be interaction or merging of different transient shocks, and the corotating shocks begin to play a role, possibly by re-accelerating some of the SEPs from transient shocks. Also, the source locations, angular distribution and radial gradient of SEP intensity are very important. In a mission to Mars, for example, the radial distance will vary according to the spacecraft trajectory chosen. The flux of SEPs is expected to vary as a power law with radial distance from the Sun, and a power-law exponent of -3 would be expected from magnetic flux tube geometry. Since the radial distance to Mars is ˜ 1.5 AU, then the flux at the orbit of Mars would be expected to be about 1/3 of the flux at 1.0 AU along the same spiral path. A consideration of these expected variations suggests that the proton prediction problem for Mars is not dramatically different from the Earth. Autonomous sensors on board the spacecraft

  5. Radiation field formation and monitoring beyond LEO

    NASA Astrophysics Data System (ADS)

    Miroshnichenko, L. I.

    This brief review comprises the main features of radiation field formation due to galactic (GCR) and solar cosmic rays (SCR) beyond low Earth orbit (LEO) in the inner Solar system. We also consider the similarities and differences of radiation environment models applicable to the Moon and Mars missions, the main requirements for radiation monitoring, warning, and forecasting techniques for deep space missions. Existing modulation models for GCR provide a possibility to estimate easily the GCR contribution to the radiation field in the interplanetary space, at the Lunar or Martian surfaces. The situation with SCR contribution is much more complicated. For space weather purposes, time profiles of the 10-30 MeV protons in the most of solar proton events (SPE), unfortunately, are often complicated by several factors, especially by interplanetary shocks driven by Coronal Mass Ejections (CME). In particular, the particle-trapping region around the shock may or may not be the region with the highest intensity of solar energetic particles (SEP), depending on whether shock acceleration continues or diminishes with distance. At distances beyond 1 AU there can be interaction or merging of different transient shocks, and the corotating shocks begin to play a role, possibly by re-accelerating some of the SEPs from transient shocks. Also, the source locations, angular distribution and radial gradient of SEP intensity are very important. In a mission to Mars, for example, the radial distance will vary according to the spacecraft trajectory chosen. The flux of SEPs is expected to vary as a power law with radial distance from the Sun, and a power-law exponent of -3 would be expected from magnetic flux tube geometry. Since the radial distance to Mars is ˜1.5 AU, then the flux at the orbit of Mars would be expected to be about 1/3 of the flux at 1.0 AU along the same spiral path in the interplanetary magnetic field (IMF). A consideration of these expected variations suggests that

  6. Starspots on LO Pegasi, 2006-2015

    NASA Astrophysics Data System (ADS)

    Harmon, Robert O.; Chalmers, Mark; Geda, Robel; Henry, Brandi; Sliupas, Viesulas

    2016-01-01

    LO Pegasi is a rapidly rotating (P = 10.154 hr) young solar analog (spectral class K5-7V) variable star of BY Dra type that exhibits dark starspots on its surface that modulate its brightness as they are carried into and out of view by the star's rotation. Surface maps of the spot distribution were produced based on BVRI photometry obtained at Perkins Observatory from 2006-2015. The maps were generated from the light curves via a non-linear inversion algorithm that uses the differences in the limb darkening through different filter passbands to improve the latitude resolution of the maps. We present an analysis of variations in the size of a polar spot suggested by changes in the average brightness and the amplitude of the rotational modulation from year to year.

  7. 77 FR 50185 - LoCorr Fund Management, LLC and LoCorr Investment Trust; Notice of Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-20

    ... shareholder approval. Applicants: LoCorr Fund Management, LLC (``LFM'' or the ``Adviser'') and LoCorr... Adviser (the ``Independent Trustees''), and by shareholders representing a majority of each of the LoCorr... Agreements will be approved by shareholders and by the Board, including a majority of the...

  8. Leo Szilard: Physics, Politics, and the Narrow Margin of Hope.

    NASA Astrophysics Data System (ADS)

    Lanouette, William

    1998-04-01

    Leo Szilard (1898-1964) was a creative physicist and biologist. But concern about how scientific discoveries might affect humanity also led him to seek political solutions to enlarge the benefits and limit the damage caused by his work. This disposition to save the world came to Szilard by the age of 10, when he read The Tragedy of Man, a Hungarian epic poem in which humanity faces extinction yet continues to survive by maintaining a narrow margin of hope. With this hope Szilard brought about improbable scientific and political feats (such as the nuclear chain reaction and the Moscow-Washington Hotline). This talk focuses on Szilard's many attempts in 1945 to prevent the atomic bombing of Japan. William Lanouette, a writer and public policy analyst, is the author of Genius in the Shadows: A Biography of Leo Szilard, The Man Behind the Bomb. (University of Chicago Press, 1994)

  9. Arcing in Leo and Geo Simulated Environments: Comparative Analysis

    NASA Technical Reports Server (NTRS)

    Vayner, Boris V.; Ferguson, Dale C.; Galofaro, Joel TY.

    2006-01-01

    Comprehensive tests of two solar array samples in simulated Low Earth Orbit (LEO) and Geosynchronous Orbit (GEO) environments have demonstrated that the arc inception voltage was 2-3 times lower in the LEO plasma than in the GEO vacuum. Arc current pulse wave forms are also essentially different in these environments. Moreover, the wide variations of pulse forms do not allow introducing the definition of a "standard arc wave form" even in GEO conditions. Visual inspection of the samples after testing in a GEO environment revealed considerable damage on coverglass surfaces and interconnects. These harmful consequences can be explained by the discharge energy being one order of magnitude higher in vacuum than in background plasma. The tests also revealed a potential danger of powerful electrostatic discharges that could be initiated on the solar array surface of a satellite in GEO during the ignition of an arcjet thruster.

  10. LEO high voltage solar array arcing response model, continuation 5

    NASA Technical Reports Server (NTRS)

    Metz, Roger N.

    1989-01-01

    The modeling of the Debye Approximation electron sheaths in the edge and strip geometries was completed. Electrostatic potentials in these sheaths were compared to NASCAP/LEO solutions for similar geometries. Velocity fields, charge densities and particle fluxes to the biased surfaces were calculated for all cases. The major conclusion to be drawn from the comparisons of our Debye Approximation calculations with NASCAP-LEO output is that, where comparable biased structures can be defined and sufficient resolution obtained, these results are in general agreement. Numerical models for the Child-Langmuir, high-voltage electron sheaths in the edge and strip geometries were constructed. Electrostatic potentials were calculated for several cases in each of both geometries. Velocity fields and particle fluxes were calculated. The self-consistent solution process was carried through one cycle and output electrostatic potentials compared to NASCAP-type input potentials.

  11. A novel unicast routing algorithm for LEO satellite networks

    NASA Astrophysics Data System (ADS)

    Song, Xuegui; Liu, Kai; Zhang, Jun; Cheng, Lianzhen

    2005-11-01

    One of research challenges in low earth orbit (LEO) satellite networks is to develop specialized and efficient routing algorithms. In this paper, a dynamic source routing algorithm (DSRA) for LEO satellite networks is presented to achieve short end-to-end delay and low computation overhead under the condition that a logical location concept is adopted to hide satellite mobility. In this algorithm, the path between source and destination with minimum propagation delay is designated by source satellite in packet header by an efficient metric < D0, n0; D1, n1; D2, n2 >. Then the packet is forwarded to its destination by intermediate nodes according to the metric. The performance of the algorithm is evaluated through simulation and its computation complexity is analyzed to validate algorithm efficiency.

  12. LEO to ground optical communications from a small satellite platform

    NASA Astrophysics Data System (ADS)

    Rose, T. S.; Janson, S. W.; LaLumondiere, S.; Werner, N.; Hinkley, D. H.; Rowen, D. W.; Fields, R. A.; Welle, R. P.

    2015-03-01

    A pair of 2.2 kg CubeSats using COTS hardware is being developed for a proof-of-principle optical communications demo from a 450-600 km LEO orbit to ground. The 10x10x15 cm platform incorporates a 25% wall-plug efficient 10-W Yb fiber transmitter emitting at 1.06 μm. Since there are no gimbals on board, the entire spacecraft is body-steered toward the ground station. The pointing accuracy of the LEO craft, which governs the data rate capability, is expected to be ~ 0.1-0.2 deg. Two optical ground stations, located at the Mt. Wilson observatory, have receiver apertures of 30 and 80 cm. Launch of the CubeSat pair is anticipated to be mid to late 2015.

  13. Volatile condensible material deposition in LEO simulated environment

    NASA Astrophysics Data System (ADS)

    Pu, Jinya

    Room Temperature Vulcanized (RTV) silicone and compounds are widely used in outer-space for bonding or potting spacecraft components. In geosynchronous equatorial orbit (GEO), the silicone may outgas species which can condense on optically sensitive surfaces and degrade their performance, therefore shortening the lifetime of spacecraft. In low-earth-orbit (LEO), the silicone rubber is subject to an energetic and corrosive environment. Atomic oxygen (AO) and ultraviolet radiation can cause abrasion and degradation of the silicone rubber, cause changes in existing condensed VCM films and affect the properties of VCM films condensing in this atmosphere. Experiments were performed to simulate GEO conditions. In this work, the outgassed effluent of RTV566 silicone condensed at three different temperatures. The VCM films were analyzed by an in-situ quartz crystal microbalance (QCM) and spectroscopic ellipsometry (SE). A self-consistent analysis approach employing the QCM and SE data has been developed to link the physical and optical properties of the condensed VCM films. It has been shown that at 120K, the VCM film contained ice, while at 150 K and 180 K, the films condense via island nucleation. Experiments were performed to simulate LEO conditions. In this work, an electron cyclotron resonance (ECR) based system was utilized to create atomic oxygen. First, VCM films were deposited in a GEO simulation chamber, then these GEO films were transferred into the ECR system for the AO exposure. Second, the AO exposure and deposition of films occurred simultaneously to produce LEO films for the first time. The results showed that the AO exposed GEO films are optically different than the LEO simulated films.

  14. Parameter Calibration of Mini-LEO Hill Slope Model

    NASA Astrophysics Data System (ADS)

    Siegel, H.

    2015-12-01

    The mini-LEO hill slope, located at Biosphere 2, is a small-scale catchment model that is used to study the ways landscapes change in response to biological, chemical, and hydrological processes. Previous experiments have shown that soil heterogeneity can develop as a result of groundwater flow; changing the characteristics of the landscape. To determine whether or not flow has caused heterogeneity within the mini-LEO hill slope, numerical models were used to simulate the observed seepage flow, water table height, and storativity. To begin a numerical model of the hill slope was created using CATchment Hydrology (CATHY). The model was then brought to an initial steady state by applying a rainfall event of 5mm/day for 180 days. Then a specific rainfall experiment of alternating intensities was applied to the model. Next, a parameter calibration was conducted, to fit the model to the observed data, by changing soil parameters individually. The parameters of the best fitting calibration were taken to be the most representative of those present within the mini-LEO hill slope. Our model concluded that heterogeneities had indeed arisen as a result of the rainfall event, resulting in a lower hydraulic conductivity downslope. The lower hydraulic conductivity downslope in turn caused in an increased storage of water and a decrease in seepage flow compared to homogeneous models. This shows that the hydraulic processes acting within a landscape can change the very characteristics of the landscape itself, namely the permeability and conductivity of the soil. In the future results from the excavation of soil in mini-LEO can be compared to the models results to improve the model and validate its findings.

  15. Reinforcement learning for resource allocation in LEO satellite networks.

    PubMed

    Usaha, Wipawee; Barria, Javier A

    2007-06-01

    In this paper, we develop and assess online decision-making algorithms for call admission and routing for low Earth orbit (LEO) satellite networks. It has been shown in a recent paper that, in a LEO satellite system, a semi-Markov decision process formulation of the call admission and routing problem can achieve better performance in terms of an average revenue function than existing routing methods. However, the conventional dynamic programming (DP) numerical solution becomes prohibited as the problem size increases. In this paper, two solution methods based on reinforcement learning (RL) are proposed in order to circumvent the computational burden of DP. The first method is based on an actor-critic method with temporal-difference (TD) learning. The second method is based on a critic-only method, called optimistic TD learning. The algorithms enhance performance in terms of requirements in storage, computational complexity and computational time, and in terms of an overall long-term average revenue function that penalizes blocked calls. Numerical studies are carried out, and the results obtained show that the RL framework can achieve up to 56% higher average revenue over existing routing methods used in LEO satellite networks with reasonable storage and computational requirements.

  16. Reinforcement learning for resource allocation in LEO satellite networks.

    PubMed

    Usaha, Wipawee; Barria, Javier A

    2007-06-01

    In this paper, we develop and assess online decision-making algorithms for call admission and routing for low Earth orbit (LEO) satellite networks. It has been shown in a recent paper that, in a LEO satellite system, a semi-Markov decision process formulation of the call admission and routing problem can achieve better performance in terms of an average revenue function than existing routing methods. However, the conventional dynamic programming (DP) numerical solution becomes prohibited as the problem size increases. In this paper, two solution methods based on reinforcement learning (RL) are proposed in order to circumvent the computational burden of DP. The first method is based on an actor-critic method with temporal-difference (TD) learning. The second method is based on a critic-only method, called optimistic TD learning. The algorithms enhance performance in terms of requirements in storage, computational complexity and computational time, and in terms of an overall long-term average revenue function that penalizes blocked calls. Numerical studies are carried out, and the results obtained show that the RL framework can achieve up to 56% higher average revenue over existing routing methods used in LEO satellite networks with reasonable storage and computational requirements. PMID:17550108

  17. Analysing the Orbital Movement and Trajectory of LEO (Low Earth Orbit) Satellite Relative to Earth Rotation

    NASA Astrophysics Data System (ADS)

    Bohra, Nafeesa; de Meer, Hermann; Memon, Aftab. A.

    Next generation of wireless Internet scenarios include LEOs (Low Earth Orbit Satellites). Lower altitudes of LEO constellations could allow global coverage while offering: low end-to-end propagation delay, low power consumption, and effective frequency usage both for the users and the satellite network. LEOs rotate asynchronously to the earth rotation. Fast movement of LEOs makes it necessary to include efficient mobility management. In past few years mobility patterns have been proposed by considering the full earth coverage constellation whereby, the rotation of earth was often assumed too negligible to be taken into account. The prime objective of this study is to provide facts and figures that show LEOs traverse relative to the rotation of earth. In order to analyse the orbital movement and trajectory of LEOs relative to earth rotation mathematical analysis have been done and justification have been made through equations.

  18. NASA-STD-4005 and NASA-HDBK-4006, LEO Spacecraft Solar Array Charging Design Standard

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.

    2007-01-01

    Two new NASA Standards are now official. They are the NASA LEO Spacecraft Charging Design Standard (NASA-STD-4005) and the NASA LEO Spacecraft Charging Design Handbook (NASA-HDBK-4006). They give the background and techniques for controlling solar array-induced charging and arcing in LEO. In this paper, a brief overview of the new standards is given, along with where they can be obtained and who should be using them.

  19. Carbon deposition characteristics of LO2/HC propellants

    NASA Technical Reports Server (NTRS)

    Hernandez, Rosemary; Mercer, Steve D.

    1987-01-01

    The generation and deposition of carbon have been studied using subscale hardware with LO2/RP-1, LO2/propane, and LO2/methane at low mixture ratio conditions. The deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60, and at chamber pressures from 720 to 1650 psia. The carbon-deposition rate is a strong function of mixture ratio and a weak function of chamber pressure. There is a mixture ratio that will minimize deposition for LO2/RP-1; a threshold mixture ratio for LO2/propane; and no deposition for LO2/methane at any mixture ratio tested. The turbine drive operating limits were defined for each fuel tested.

  20. An Update on the Effectiveness of Postmission Disposal in LEO

    NASA Technical Reports Server (NTRS)

    Liou, J.-C.

    2013-01-01

    The commonly-adopted orbital debris mitigation measures were developed to reduce the growth of the future debris population. A major component in debris mitigation is post-mission disposal (PMD). The key PMD element for LEO satellites is the 25-year rule. It is intended to limit the long-term presence of rocket bodies (R/Bs) and spacecraft (S/C), as well as mission-related debris, in the environment. The effectiveness of PMD has been demonstrated and documented since the development of mitigation measures began in the 1990s. This paper summarizes an updated study, based on the current environment, using the NASA LEGEND model. The study focused on the > or = 10 cm population in LEO. The historical simulation covered 1957 through 2011 and followed the recorded launches and known breakup events. The future projection was carried out for 200 years. An eight-year launch traffic, 2004 - 2011, was repeated during the projection period. An eight-year mission lifetime was assumed for future S/C. No stationkeeping and no collision avoidance maneuver were implemented. Only objects 10 cm and larger were included in collision consideration. No explosion was allowed for R/Bs and S/C launched after 2011. The 25-year PMD rule success rates were set at 0%, 10%, 50%, 75%, and 95%, respectively, for the 5 study scenarios. Results of the simulations were analyzed to quantify the differences among the different compliance rates. As expected, the 0% PMD projection followed a rapid and non-linear increase in the next 200 years. The LEO population, on average, more than tripled at the end of the simulations. With a 50% compliance of the 25-year rule, the population growth was reduced approximately by half. However, even with a 95% compliance of the 25-year rule, the LEO debris population would still increase by an average of more than 50% in 200 years. These simulation results provide an updated assessment of the effectiveness of the 25-year rule. It is the first and the most cost

  1. The ESA-ANISAP Study: Estimate Of Troospheric Scintillation Along A LEO-LEO Link Through High Resolution Radiosonde Data

    NASA Astrophysics Data System (ADS)

    Martini, Enrica; Freni, Angelo; Facheris, Luca; Cuccoli, Fabrizio

    2013-12-01

    This work describes the procedure developed in the framework of the ESA-ANISAP study to obtain, for a given atmospheric profile, an estimate of scintillation effects in a LEO-LEO link. In this procedure, the refractive-index structure constant profiles describing the intensity of turbulence, are derived by applying the vertical gradient approach to high resolution radiosonde data. The fact that turbulence in the free atmosphere is confined to vertically thin layers is accounted for by identifying the turbulent layers through the analysis of the Richardson number profiles. Then, the derived structure constant profiles are inserted into a parametric scintillation model to create a scintillation disturbance estimate consistent with the considered atmospheric profile. In the parametric model, the troposphere is described as a spherically symmetric turbulent medium. Rytov's first iteration solution for weak fluctuations is used to derive an expression for two quantities of interest to evaluate the performances of the Normalized Differential Spectral Attenuation for the estimate of the total content of water vapour along the propagation path between two LEO satellite, namely: the variance of amplitude fluctuations of the wave and the correlation between the fluctuations at different frequencies. The influence on these quantities of some turbulence characteristics which are not known with confidence, like the outer scale length and the behaviour of the spectrum in the input range, is also investigated.

  2. Como Lo Hago Yo: Mielomeningocele En Bolivia

    PubMed Central

    Dabdoub, Carlos F.; Dabdoub, Carlos B.; Villavicencio, Ramiro; Quevedo, Germán

    2014-01-01

    Introducción: Las malformaciones del tubo neural (MTN) representan la segunda causa más frecuente de anomalías congénitas, luego de las cardiopatías. En este grupo se destaca el mielomeningocele (MMC) por su mayor incidencia, y por ser la más incapacitante y la más compleja entre todas las demás malformaciones del sistema nervioso c`entral (SNC). En Bolivia, como en muchos países de Sudamérica, los bajos niveles socio-culturales y la debilidad en el sistema sanitario, hacen que su incidencia y su morbilidad, sean mayores que en las naciones más desarrolladas. Material y Métodos: Se realizó un estudio retrospectivo y descriptivo de 70 casos de MMC, atendidos por un equipo multidisciplinario en el Hospital Universitario Japonés (HUJ) de Santa Cruz de la Sierra, entre 2008-2011. De ellos, 60 fueron intervenidos quirúrgicamente. Resultados: Se realizaron controles prenatales sólo en 27 mujeres (38.6%), diagnosticándose una disrafia espinal en apenas dos casos (7.4%). La edad de ingreso del MMC en su mayoría fue después de las 24 horas (65.6%), predominando su localización en la región lumbosacra (64.3%). De ellos, 67.2% eran abiertos, presentando un 32.9% un daño neurológico motor parcial mientras que 47.1% tenían paraplejia por debajo de la lesión. De los 70 casos, tres (4.3%) no fueron intervenidos, por presentar defectos congénitos severos o estado general grave. Las principales complicaciones posoperatorias inmediatas fueron: dehiscencia de sutura y/o infección de la herida (16.6%), fístula de líquido cefalorraquídeo (LCR) (10%) e infección del SNC (11.7%). La mortalidad general y postoperatoria fue de 7.1% y 3.3%, respectivamente. Al mes de vida presentaban hidrocefalia un 80% de los pacientes operados, colocándose una derivación ventriculoperitoneal (DVP) de presión media. De 9 pacientes que tuvieron un acompanamiento de dos o más años, seis presentaron una médula anclada, que fueron intervenidas quirúrgicamente. Conclusi

  3. Massive star formation within the Leo 'primordial' ring.

    PubMed

    Thilker, David A; Donovan, Jennifer; Schiminovich, David; Bianchi, Luciana; Boissier, Samuel; de Paz, Armando Gil; Madore, Barry F; Martin, D Christopher; Seibert, Mark

    2009-02-19

    Few intergalactic, plausibly primordial clouds of neutral atomic hydrogen (H(i)) have been found in the local Universe, suggesting that such structures have either dispersed, become ionized or produced a stellar population on gigayear timescales. The Leo ring, a massive (M(H(i)) approximately 1.8 x 10(9)M[symbol: see text], M[symbol: see text] denoting the solar mass), 200-kpc-wide structure orbiting the galaxies M105 and NGC 3384 with a 4-Gyr period, is a candidate primordial cloud. Despite repeated atttempts, it has previously been seen only from H i emission, suggesting the absence of a stellar population. Here we report the detection of ultraviolet light from gaseous substructures of the Leo ring, which we attribute to recent massive star formation. The ultraviolet colour of the detected complexes is blue, implying the onset of a burst of star formation or continuous star formation of moderate (approximately 10(8)-yr) duration. Measured ultraviolet-visible photometry favours models with low metallicity (Z approximately Z[symbol: see text]/50-Z[symbol: see text]/5, Z[symbol: see text] denoting the solar metallicity), that is, a low proportion of elements heavier than helium, although spectroscopic confirmation is needed. We speculate that the complexes are dwarf galaxies observed during their formation, but distinguished by their lack of a dark matter component. In this regard, they resemble tidal dwarf galaxies, although without the enrichment preceding tidal stripping. If structures like the Leo ring were common in the early Universe, they may have produced a large, yet undetected, population of faint, metal-poor, halo-lacking dwarf galaxies.

  4. Lo/Ld phase coexistence modulation induced by GM1.

    PubMed

    Puff, Nicolas; Watanabe, Chiho; Seigneuret, Michel; Angelova, Miglena I; Staneva, Galya

    2014-08-01

    Lipid rafts are assumed to undergo biologically important size-modulations from nanorafts to microrafts. Due to the complexity of cellular membranes, model systems become important tools, especially for the investigation of the factors affecting "raft-like" Lo domain size and the search for Lo nanodomains as precursors in Lo microdomain formation. Because lipid compositional change is the primary mechanism by which a cell can alter membrane phase behavior, we studied the effect of the ganglioside GM1 concentration on the Lo/Ld lateral phase separation in PC/SM/Chol/GM1 bilayers. GM1 above 1mol % abolishes the formation of the micrometer-scale Lo domains observed in GUVs. However, the apparently homogeneous phase observed in optical microscopy corresponds in fact, within a certain temperature range, to a Lo/Ld lateral phase separation taking place below the optical resolution. This nanoscale phase separation is revealed by fluorescence spectroscopy, including C12NBD-PC self-quenching and Laurdan GP measurements, and is supported by Gaussian spectral decomposition analysis. The temperature of formation of nanoscale Lo phase domains over an Ld phase is determined, and is shifted to higher values when the GM1 content increases. A "morphological" phase diagram could be made, and it displays three regions corresponding respectively to Lo/Ld micrometric phase separation, Lo/Ld nanometric phase separation, and a homogeneous Ld phase. We therefore show that a lipid only-based mechanism is able to control the existence and the sizes of phase-separated membrane domains. GM1 could act on the line tension, "arresting" domain growth and thereby stabilizing Lo nanodomains. PMID:24835016

  5. LEO effects on candidate solar cell cover materials

    NASA Technical Reports Server (NTRS)

    Stella, Paul M.

    1993-01-01

    In 1984, the LDEF (Long Duration Exposure Facility) was placed in LEO (Low Earth Orbit) for a mission planned to last approximately one year. Due to a number of factors, retrieval was delayed until 1990. An experiment, prepared under the direction of JPL, consisted of a test plate with thirty (30) individual thin silicon solar cell/cover samples. The covers consisted of conventional cerium doped microsheet platelets and potential candidate materials, such as FEP Teflon, silicon RTV's, glass resins, polyimides, and a silicone-polyimide copolymer encapsulant. The effects of the LDEF mission environment (micrometeorite/debris impacts, atomic oxygen, UV, and particulate radiation) on the samples are discussed.

  6. Haemangiosarcoma in a captive Asiatic lion (Panthera leo persica).

    PubMed

    Vercammen, F; Brandt, J; Brantegem, L Van; Bosseler, L; Ducatelle, R

    2015-01-01

    A 2.7-year-old male captive Asiatic lion (Panthera leo persica) died unexpectedly without preceding symptoms. Gross necropsy revealed liver and lung tumours, which proved to be haemangiosarcomas by histopathology. Some of the liver tumours were ruptured, leading to massive intra-abdominal haemorrhage and death. Haemangiosarcomas are rare in domestic and exotic felids, occurring in skin, thoracic-abdominal cavity and bones. Although these tumours mainly appear to be occurring in older cats, they are sometimes observed in younger animals, as in the present case. This is the first description of haemangiosarcoma in a young Asiatic lion. PMID:26623366

  7. LEO-to-GEO low thrust chemical propulsion

    NASA Technical Reports Server (NTRS)

    Shoji, J. M.

    1980-01-01

    One approach being considered for transporting large space structures from low Earth orbit (LEO) to geosynchronous equatorial orbit (GEO) is the use of low thrust chemical propulsion systems. A variety of chemical rocket engine cycles evaluated for this application for oxygen/hydrogen and oxygen/hydrocarbon propellants (oxygen/methane and oxygen/RF-1) are discussed. These cycles include conventional propellant turbine drives, turboalternator/electric motor pump drive, and fuel cell/electric motor pump drive as well as pressure fed engines. Thrust chamber cooling analysis results are presented for regenerative/radiation and film/radiation cooling.

  8. Haemangiosarcoma in a captive Asiatic lion (Panthera leo persica)

    PubMed Central

    Vercammen, F.; Brandt, J.; Brantegem, L. Van; Bosseler, L.; Ducatelle, R.

    2015-01-01

    A 2.7-year-old male captive Asiatic lion (Panthera leo persica) died unexpectedly without preceding symptoms. Gross necropsy revealed liver and lung tumours, which proved to be haemangiosarcomas by histopathology. Some of the liver tumours were ruptured, leading to massive intra-abdominal haemorrhage and death. Haemangiosarcomas are rare in domestic and exotic felids, occurring in skin, thoracic-abdominal cavity and bones. Although these tumours mainly appear to be occurring in older cats, they are sometimes observed in younger animals, as in the present case. This is the first description of haemangiosarcoma in a young Asiatic lion. PMID:26623366

  9. 20 CFR 10.736 - What are the time limits for filing a LEO claim?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false What are the time limits for filing a LEO claim? 10.736 Section 10.736 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS, DEPARTMENT OF... limits for filing a LEO claim? OWCP must receive a claim for benefits under 5 U.S.C. 8191 within...

  10. Judicial Rhetoric in a Fragmentary World: "Character" and Storytelling in the Leo Frank Case.

    ERIC Educational Resources Information Center

    Hasian, Marouf, Jr.

    1997-01-01

    Uses the 1913 murder trial of Leo Frank to examine the ways in which "characters" are developed in legal discourse. Focuses attention on the ways in which race, class, and gender are constructed in discussions of Leo Frank's guilt or innocence. Highlights the rhetorical dimensions of direct and cross-examination, closing statements, and press…

  11. 20 CFR 10.738 - Under what circumstances are benefits payable in LEO claims?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false Under what circumstances are benefits payable in LEO claims? 10.738 Section 10.738 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS... circumstances are benefits payable in LEO claims? (a) Benefits are payable when an officer is injured...

  12. LEO: A Learning Environment Organizer to Support Computer-Mediated Instruction

    ERIC Educational Resources Information Center

    Coffey, John W.; Canas, Alberto J.

    2003-01-01

    This article contains a description of a network-based Learning Environment Organizer entitled LEO, which takes its impetus from the Assimilation Theory of meaningful learning. LEO represents a new approach to computer-mediated augmentation of face-to-face, or hybrid courses, and a different approach to distance learning course delivery. LEO…

  13. The Sublime Corpse in Gertrudis Gomez de Avellaneda's Women's Journal "Album Cubano de lo Bueno y lo Bello" (1860)

    ERIC Educational Resources Information Center

    LaGreca, Nancy

    2009-01-01

    This article examines Gertrudis Gomez de Avellaneda's choice to include articles depicting the advanced decay of cadavers, which are simultaneously horrible and awesome, in her women's periodical "Album Cubano de lo Bueno y lo Bello". Background on Avellaneda's biography, women's print culture, and theories of the sublime provide a frame for the…

  14. Telemetry Tracking & Control (TT&C) - First TDRSS, then Commercial GEO & Big LEO and Now Through LEO

    NASA Technical Reports Server (NTRS)

    Morgan, Dwayne R.; Streich, Ron G.; Bull, Barton; Grant, Chuck; Power, Edward I. (Technical Monitor)

    2001-01-01

    The advent of low earth orbit (LEO) commercial communication satellites provides an opportunity to dramatically reduce Telemetry, Tracking and Control (TT&C) costs of launch vehicles, Unpiloted Aerial Vehicles (UAVs), Research Balloons and spacecraft by reducing or eliminating ground infrastructure. Personnel from the Goddard Space Flight Center's Wallops Flight Facility (GSFC\\WFF) have successfully used commercial Geostationary Earth Orbit (GEO) and Big LEO communications satellites for Long Duration Balloon Flight TT&C. The Flight Modem is a GSFC\\WFF Advanced Range Technology initiative (ARTI) designed to streamline TT&C capability in the user community of these scientific data gathering platforms at low cost. Making use of existing LEO satellites and adapting and ruggedized commercially available components; two-way, over the horizon communications may be established with these vehicles at great savings due to reduced infrastructure. Initially planned as a means for permitting GPS data for tracking and recovery of sounding rocket and balloon payloads, expectations are that the bandwidth can soon be expanded to allow more comprehensive data transfer. The system architecture which integrates antennas, GPS receiver, commercial satellite packet data modem and a single board computer with custom software is described and technical challenges are discussed along with the plan for their resolution. A three-phase testing and development plan is outlined and the current results are reported. Results and status of ongoing flight tests on aircraft and sounding rockets are reported. Future applications on these platforms and the potential for satellite support are discussed along with an analysis of cost effectiveness of this method vs. other tracking and data transmission schemes.

  15. The PAF1 complex component Leo1 is essential for cardiac and neural crest development in zebrafish.

    PubMed

    Nguyen, Catherine T; Langenbacher, Adam; Hsieh, Michael; Chen, Jau-Nian

    2010-05-01

    Leo1 is a component of the Polymerase-Associated Factor 1 (PAF1) complex, an evolutionarily conserved protein complex involved in gene transcription regulation and chromatin remodeling. The role of leo1 in vertebrate embryogenesis has not previously been examined. Here, we report that zebrafish leo1 encodes a nuclear protein that has a similar molecular structure to Leo1 proteins from other species. From a genetic screen, we identified a zebrafish mutant defective in the leo1 gene. The truncated Leo1(LA1186) protein lacks a nuclear localization signal and is distributed mostly in the cytoplasm. Phenotypic analysis showed that while the initial patterning of the primitive heart tube is not affected in leo1(LA1186) mutant embryos, the differentiation of cardiomyocytes at the atrioventricular boundary is aberrant, suggesting a requirement for Leo1 in cardiac differentiation. In addition, the expression levels of markers for neural crest-derived cells such as crestin, gch2, dct and mitfa are greatly reduced in leo1(LA1186) mutants, indicating a requirement for Leo1 in maintaining the neural crest population. Consistent with this finding, melanocyte and xanthophore populations are severely reduced, craniofacial cartilage is barely detectable, and mbp-positive glial cells are absent in leo1(LA1186) mutants after three days of development. Taken together, these results provide the first genetic evidence of the requirement for Leo1 in the development of the heart and neural crest cell populations.

  16. Modeling of LEO orbital debris populations for ORDEM2008

    NASA Astrophysics Data System (ADS)

    Xu, Y.-L.; Horstman, M.; Krisko, P. H.; Liou, J.-C.; Matney, M.; Stansbery, E. G.; Stokely, C. L.; Whitlock, D.

    2009-03-01

    The NASA Orbital Debris Engineering Model, ORDEM2000, is in the process of being updated to a new version: ORDEM2008. The data-driven ORDEM covers a spectrum of object size from 10 μm to greater than 1 m, and ranging from LEO (low Earth orbit) to GEO (geosynchronous orbit) altitude regimes. ORDEM2008 centimeter-sized populations are statistically derived from Haystack and HAX (the Haystack Auxiliary) radar data, while micron-sized populations are estimated from shuttle impact records. Each of the model populations consists of a large number of orbits with specified orbital elements, the number of objects on each orbit (with corresponding uncertainty), and the size, type, and material assignment for each object. This paper describes the general methodology and procedure commonly used in the statistical inference of the ORDEM2008 LEO debris populations. Major steps in the population derivations include data analysis, reference-population construction, definition of model parameters in terms of reference populations, linking model parameters with data, seeking best estimates for the model parameters, uncertainty analysis, and assessment of the outcomes. To demonstrate the population-derivation process and to validate the Bayesian statistical model applied in the population derivations throughout, this paper uses illustrative examples for the special cases of large-size (>1 m, >32 cm, and >10 cm) populations that are tracked by SSN (the Space Surveillance Network) and also monitored by Haystack and HAX radars operating in a staring mode.

  17. Spectrometric and photometric study of the eclipsing variable AM Leo

    NASA Astrophysics Data System (ADS)

    Gorda, S. Yu.

    2016-01-01

    The results of quasi-simultaneous spectroscopic and photometric observations of a W UMatype eclipsing variable star AM Leo are presented. The observations were carried out with a 1.2-m telescope equipped with a high-resolution echelle spectrometer, and a telescope-reflector ( D = 0.45m) of the Kourovka Astronomical Observatory of Ural Federal University. New values of semi-amplitudes of the radial velocity curves of the components, K 1 = 109.6kms-1 and K 2 = 252.4kms-1 and the systemic radial velocity V 0 =-9.3 kms-1 are obtained, comparable to the data published in the literature. The semi-amplitude of the radial velocity curve of a more massive component K 1 and the mass ratio of the components q = 0.412 appeared to be slightly smaller than the values obtained by other authors. An assumption wasmade that a possible reason of this is the presence of hot and/or cold spots on the surface of the components, shifting the effective center of brightness of the visible disk of the component with respect to its center of mass position. It was shown that the AM Leo light curve variations on the time scales of one and more days, registered within the photometric part of the study may be described by the choice of appropriate model of the spot structure.

  18. MEMS Reaction Control and Maneuvering for Picosat Beyond LEO

    NASA Technical Reports Server (NTRS)

    Alexeenko, Alina

    2016-01-01

    The MEMS Reaction Control and Maneuvering for Picosat Beyond LEO project will further develop a multi-functional small satellite technology for low-power attitude control, or orientation, of picosatellites beyond low Earth orbit (LEO). The Film-Evaporation MEMS Tunable Array (FEMTA) concept initially developed in 2013, is a thermal valving system which utilizes capillary forces in a microchannel to offset internal pressures in a bulk fluid. The local vapor pressure is increased by resistive film heating until it exceeds meniscus strength in a nozzle which induces vacuum boiling and provides a stagnation pressure equal to vapor pressure at that point which is used for propulsion. Interplanetary CubeSats can utilize FEMTA for high slew rate attitude corrections in addition to desaturating reaction wheels. The FEMTA in cooling mode can be used for thermal control during high-power communication events, which are likely to accompany the attitude correction. Current small satellite propulsion options are limited to orbit correction whereas picosatellites are lacking attitude control thrusters. The available attitude control systems are either quickly saturated reaction wheels or movable high drag surfaces with long response times.

  19. An active debris removal parametric study for LEO environment remediation

    NASA Astrophysics Data System (ADS)

    Liou, J.-C.

    2011-06-01

    Recent analyses on the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited interest in using active debris removal (ADR) to remediate the environment. There are, however, monumental technical, resource, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of its effectiveness must be conducted. The goal is to demonstrate the need and feasibility of using ADR to better preserve the future environment and to explore different operational options to maximize the benefit-to-cost ratio. This paper describes a new sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term orbital debris evolutionary model, LEGEND, is used to quantify the effects of several key parameters, including target selection criteria/constraints and the starting epoch of ADR implementation. Additional analyses on potential ADR targets among the existing satellites and the benefits of collision avoidance maneuvers are also included.

  20. Beller Lecture: The Roots of Leo Szilard and his Interdisciplinarity

    NASA Astrophysics Data System (ADS)

    Marx, George

    1998-04-01

    A Central European among the whites was said about Leo Szilard who originated from a polycultural family. In the early 20th century he grew up in Hungary, at the crossroads of history, where political regimes, national borders, ideological doctrines, ``final truths'' changed in a dizzying cavalcade. Instead of conservative dogmatism this social environment required critical thinking in order to survive. World War I was the school of Theodore von Kármán, John von Neumann, Eugene P. Wigner and Leo Szilard; each of them learned trespassing political and disciplinary boundaries without inhibition. Their sensitivity for trends had been utilized by the United States when war efforts and high tech required orientation under new horizons. Szilard's interest ranged from statistical physics through information theory to biological evolution, from life phenomena through hot atoms to nuclear strategy. His intellectual adventures might look crazy jumps for specialists. But now, looking back to the political and technological history of the 20th century one can see than it was a consequent progress of a future-sensitive mind.

  1. Radiation environment at LEO orbits: MC simulation and experimental data.

    NASA Astrophysics Data System (ADS)

    Zanini, Alba; Borla, Oscar; Damasso, Mario; Falzetta, Giuseppe

    The evaluations of the different components of the radiation environment in spacecraft, both in LEO orbits and in deep space is of great importance because the biological effect on humans and the risk for instrumentation strongly depends on the kind of radiation (high or low LET). That is important especially in view of long term manned or unmanned space missions, (mission to Mars, solar system exploration). The study of space radiation field is extremely complex and not completely solved till today. Given the complexity of the radiation field, an accurate dose evaluation should be considered an indispensable part of any space mission. Two simulation codes (MCNPX and GEANT4) have been used to assess the secondary radiation inside FO-TON M3 satellite and ISS. The energy spectra of primary radiation at LEO orbits have been modelled by using various tools (SPENVIS, OMERE, CREME96) considering separately Van Allen protons, the GCR protons and the GCR alpha particles. This data are used as input for the two MC codes and transported inside the spacecraft. The results of two calculation meth-ods have been compared. Moreover some experimental results previously obtained on FOTON M3 satellite by using TLD, Bubble dosimeter and LIULIN detector are considered to check the performances of the two codes. Finally the same experimental device are at present collecting data on the ISS (ASI experiment BIOKIS -nDOSE) and at the end of the mission the results will be compared with the calculation.

  2. Exploration Atmospheres for Beyond-LEO Human Exploration Missions

    NASA Technical Reports Server (NTRS)

    Henninger, Donald, L.

    2013-01-01

    Atmospheric pressure and oxygen concentration of human-occupied space vehicles and habitats are an important life support parameter. The atmosphere is critical in terms of not only safety but also in terms of maximizing human capabilities at the point of scientific discovery. Human exploration missions beyond low earth orbit (LEO) will include extravehicular activity (EVA). EVAs are carried out in low pressure (4.3 psi/29.6 kilopascals) space suits running at 100 percent oxygen. New suits currently in development will be capable of running at a range of pressures between approximately 8.2 psi/56.5 kilopascals and 4.3 psi/29.6 kilopascals. In order to carry out high-frequency EVA phases of a mission safely and more efficiently, it is advantageous to have cabin or vehicle atmospheres at lower total pressure and higher oxygen concentrations. This allows for much reduced pre-breathe times for a fixed risk of decompression sickness and thus more efficient EVAs. The recommended oxygen concentration is 32% and represents a trade with respect to controlling the risk of decompression sickness and risk of fire. Work carried out by NASA in 2006 and continued in 2012 established an atmospheric pressure and oxygen concentration to optimize EVA. This paper will review previous work and describe current recommendations for beyond-LEO human exploration missions.

  3. Low-z LoBAL QSOs: orientation or evolution?

    NASA Astrophysics Data System (ADS)

    Lazarova, M.

    2015-09-01

    Low-ionization Broad Absorption Line QSOs (LoBALs) are redder type-1 QSOs characterized by broad, blue-shifted absorptions of Mg II, indicating gas outflows at velocities up to 0.2c. There is still much debate regarding the nature of these objects. In the orientation paradigm, LoBALs are present in all QSOs, but can only be observed along limited lines of sight that skim the obscuring torus. Conversely, in the evolution paradigm LoBALS have been interpreted as being a short phase in the early stages of the QSO lifecycle, when QSO-driven winds are expelling gas and dust from the central regions. To explore the suggestion by previous work that LoBALS are more likely to be observed in mergers and recently fueled QSOs, we conducted a morphological analysis of a volume-limited sample of 22 SDSS-selected LoBALs at 0.5 < z < 0.6 using HST/WFC3. We find signs of recent or ongoing tidal interaction in 2/3 of the host galaxies, and detailed surface brightness analysis with GALFIT indicates that the vast majority have early-type morphologies. Our results confirm the high rate of mergers in LoBAL hosts and they further show that LoBALs can be observed at any stage of the merger when QSO activity is expected, according to numerical simulations. While the morphologies of these objects may support the evolution paradigm, their SEDs do not suggest they are a population of QSOs statistically different from optically-selected type-1 QSOs. We discuss the two possible explanations for LoBALs implied by our results.

  4. LoFASM's FPGA-based Digital Acquisition System

    NASA Astrophysics Data System (ADS)

    Dartez, Louis P.; Jenet, F.; Creighton, T. D.; Ford, A. J.; Hicks, B.; Hinojosa, J.; Kassim, N. E.; Price, R. H.; Stovall, K.; Ray, P. S.; Taylor, G. B.

    2014-01-01

    The Low Frequency All Sky Monitor (LoFASM) is a distributed array of dipole antennas that are sensitive to radio frequencies from 10 to 88 MHz. LoFASM consists of antennas and front end electronics that were originally developed for the Long Wavelength Array (LWA) by the U.S. Naval Research Lab, the University of New Mexico, Virginia Tech, and the Jet Propulsion Laboratory. LoFASM, funded by the U.S. Department of Defense, will initially consist of 4 stations, each consisting of 12 dual-polarization dipole antenna stands. The primary science goals of LoFASM will be the detection and study of low-frequency radio transients, a high priority science goal as deemed by the National Research Council's decadal survey. The data acquisition system for the LoFASM antenna array will be using Field Programmable Gate Array (FPGA) technology to implement a real time full Stokes spectrometer and data recorder. This poster presents an overview of the current design and digital architecture of a single station of the LoFASM array as well as the status of the entire project.

  5. Charging of space debris in the LEO and GEO regions

    NASA Astrophysics Data System (ADS)

    Sen, Abhijit; Tiwari, Sanat Kumar

    The near exponential rise of space debris at the satellite orbital altitudes (particularly in the low earth orbit (LEO) region) and the risk they pose for space assets is a source of major concern for all nations engaged in space activities. Considerable efforts are therefore being expended into accurate modeling and tracking of these objects and various ideas for the safe removal of these debris are being explored. The debris objects are likely to acquire a large amount of charge since they are typically found in a plasma environment - such as the earth’s ionospheric plasma in the LEO region (100 kms to 1000 kms) and the radiation belts in the geosynchronous orbit (GEO) region. The consequent flow of electron and ion currents on them lead to the accumulation of a large amount of surface charge and the development of a surface potential on these objects. The influence of the plasma environment on the dynamics and charging of the debris is a relatively unexplored area of Space Situational Awareness (SSA) and Space Debris (SD) research and can be potentially important for the accurate prediction of the long-term evolution of debris orbits and their collision probabilities with other space objects. In this paper we will report on the charging of space debris under a variety of orbital conditions in the LEO and GEO regions using both analytic and particle-in-cell (PIC) modeling. The analytic estimates are obtained using refined Orbit Motion Limited (OML) modeling while the simulation studies are carried out using the SPIS code [1]. In the GEO region account is taken of charging due to photoemission processes as well as energetic beam charging. The PIC approach enables us to study charging of irregularly shaped debris objects as well as differential charging on objects that are composed of patches of conducting and insulated regions. The dynamical consequences of the debris charging on their orbital trajectories and rotational characteristics will be discussed. [1] J

  6. Global tracking and inventory of military hardware via LEO satellite: A system approach and likely scenario

    NASA Technical Reports Server (NTRS)

    Bell, David; Estabrook, Polly; Romer, Richard

    1995-01-01

    A system for global inventory control of electronically tagged military hardware is achievable using a LEO satellite constellation. An equipment Tag can communicate directly to the satellite with a power of 5 watts or less at a data rate of 2400 to 50,000 bps. As examples, two proposed commercial LEO systems, IRIDIUM and ORBCOMM, are both capable of providing global coverage but with dramatically different telecom capacities. Investigation of these two LEO systems as applied to the Tag scenario provides insight into satellite design trade-offs, constellation trade-offs and signal dynamics that effect the performance of a satellite-based global inventory control system.

  7. LEGEND, a LEO-to-GEO Environment Debris Model

    NASA Technical Reports Server (NTRS)

    Liou, Jer Chyi; Hall, Doyle T.

    2013-01-01

    LEGEND (LEO-to-GEO Environment Debris model) is a three-dimensional orbital debris evolutionary model that is capable of simulating the historical and future debris populations in the near-Earth environment. The historical component in LEGEND adopts a deterministic approach to mimic the known historical populations. Launched rocket bodies, spacecraft, and mission-related debris (rings, bolts, etc.) are added to the simulated environment. Known historical breakup events are reproduced, and fragments down to 1 mm in size are created. The LEGEND future projection component adopts a Monte Carlo approach and uses an innovative pair-wise collision probability evaluation algorithm to simulate the future breakups and the growth of the debris populations. This algorithm is based on a new "random sampling in time" approach that preserves characteristics of the traditional approach and captures the rapidly changing nature of the orbital debris environment. LEGEND is a Fortran 90-based numerical simulation program. It operates in a UNIX/Linux environment.

  8. CLINICOPATHOLOGIC FEATURES OF MAMMARY MASSES IN CAPTIVE LIONS (PANTHERA LEO).

    PubMed

    Sadler, Ryan A; Craig, Linden E; Ramsay, Edward C; Helmick, Kelly; Collins, Darin; Garner, Michael M

    2016-03-01

    A multi-institutional retrospective analysis of 330 pathology accessions from 285 different lions found 15 captive, female African lions (Panthera leo) with confirmed mammary masses. Aside from the presence of a mammary mass, the most common initial clinical sign was inappetence. Histologic diagnoses were predominantly adenocarcinoma (n = 12), though two benign masses (mammary hyperplasia and a mammary cyst) and one squamous cell carcinoma were identified. Nine of 13 malignant tumors had metastasized to lymph nodes or viscera at the time of necropsy. Six lions with adenocarcinoma and two lions with benign mammary masses had received hormonal contraception, though little evidence of mammary lobular hyperplasia was seen in association with the adenocarcinomas. The most common concurrent disease processes found at necropsy were chronic urinary tract disease and other malignancies. These cases demonstrate that mammary malignancies occur in captive lions and frequently metastasize.

  9. Discovery of a tidal dwarf galaxy in the Leo Triplet

    SciTech Connect

    Nikiel-Wroczyński, B.; Soida, M.; Urbanik, M.; Bomans, D. J. E-mail: soida@oa.uj.edu.pl E-mail: bomans@astro.rub.de

    2014-05-10

    We report the discovery of a dwarf galaxy in the Leo Triplet. Analysis of the neutral hydrogen distribution shows that it rotates independently of the tidal tail of NGC 3628, with a radial velocity gradient of 35-40 km s{sup –1} over approximately 13 kpc. The galaxy has an extremely high neutral gas content, accounting for a large amount of its total dynamic mass and suggesting a low amount of dark matter. It is located at the tip of the gaseous tail, which strongly suggests a tidal origin. If this is the case, it would be one of the most confident and nearest (to the Milky Way) detections of a tidal dwarf galaxy and, at the same time, the object most detached from its parent galaxy (≈140 kpc) of this type.

  10. The final analysis Little Leo: A system and service overview

    NASA Astrophysics Data System (ADS)

    Fatig, Michael

    1997-01-01

    There is an emerging commercial space industry consisting of constellations of low earth orbiting satellites to that will provide global telecommunications services. Within the set of proposed low earth orbiting satellite systems, there exists two distinct classes. One class provides high bandwidth digital voice and data services, and the other provides narrowband store and forward digital data services. The digital data service systems are called Little LEOs or Infosats. These systems will provide a variety of personal, business, environmental, and industrial digital data services on a global scale. Infosat systems provide a niche telecommunications infrastructure that benefit industries and governments of the world whether developing or industrialized; geographically homogeneous or diverse; or low, middle, or high income. The flexible nature of the service allows it to be applied in many ways to meet changing needs. This paper provides an overview of the Final Analysis Infosat system.

  11. Next Generation Grating Spectrometer Sounders for LEO and GEO

    NASA Technical Reports Server (NTRS)

    Pagano, Thomas S.

    2011-01-01

    AIRS and MODIS are widely used for weather, climate, composition, carbon cycle, cross-calibration, and applications. The community asking for new capability in the 2020 timeframe, capabilities desired: (1) Hyperspectral UV to LWIR, High Spatial ?1km IFOV (2) Maximize Synergies of Solar Reflected and IR. Synergies with OCO-2. We expect more users and applications of next gen LEO IR Sounder than GEO. These include: weather, climate, GHG monitoring, aviation, disaster response. There is a new direction for imagers and sounders: (1) Separate Vis/NIR/SWIR from MWIR/LWIR instruments reduces technology risk and complexity. (2) Expect Costs to be lower than CrIS & VIIRS Some additional ideas to reduce costs include: (1) minimum set of requirements (2) mini-grating spectrometers. supports constellation for higher revisit (3) new technology to reduce instrument size (large format fpa's) (4) hosted payloads

  12. Leo Spacecraft Charging Design Guidelines: A Proposed NASA Standard

    NASA Technical Reports Server (NTRS)

    Hillard, G. B.; Ferguson, D. C.

    2004-01-01

    Over the past decade, Low Earth Orbiting (LEO) spacecraft have gradually required ever-increasing power levels. As a rule, this has been accomplished through the use of high voltage systems. Recent failures and anomalies on such spacecraft have been traced to various design practices and materials choices related to the high voltage solar arrays. NASA Glenn has studied these anomalies including plasma chamber testing on arrays similar to those that experienced difficulties on orbit. Many others in the community have been involved in a comprehensive effort to understand the problems and to develop practices to avoid them. The NASA Space Environments and Effects program, recognizing the timeliness of this effort, commissioned and funded a design guidelines document intended to capture the current state of understanding. This document, which was completed in the spring of 2003, has been submitted as a proposed NASA standard. We present here an overview of this document and discuss the effort to develop it as a NASA standard.

  13. CLINICOPATHOLOGIC FEATURES OF MAMMARY MASSES IN CAPTIVE LIONS (PANTHERA LEO).

    PubMed

    Sadler, Ryan A; Craig, Linden E; Ramsay, Edward C; Helmick, Kelly; Collins, Darin; Garner, Michael M

    2016-03-01

    A multi-institutional retrospective analysis of 330 pathology accessions from 285 different lions found 15 captive, female African lions (Panthera leo) with confirmed mammary masses. Aside from the presence of a mammary mass, the most common initial clinical sign was inappetence. Histologic diagnoses were predominantly adenocarcinoma (n = 12), though two benign masses (mammary hyperplasia and a mammary cyst) and one squamous cell carcinoma were identified. Nine of 13 malignant tumors had metastasized to lymph nodes or viscera at the time of necropsy. Six lions with adenocarcinoma and two lions with benign mammary masses had received hormonal contraception, though little evidence of mammary lobular hyperplasia was seen in association with the adenocarcinomas. The most common concurrent disease processes found at necropsy were chronic urinary tract disease and other malignancies. These cases demonstrate that mammary malignancies occur in captive lions and frequently metastasize. PMID:27010273

  14. LEO atomic oxygen effects on spacecraft materials: STS-5 results

    NASA Technical Reports Server (NTRS)

    Whitaker, A. F.

    1984-01-01

    Effects of low Earth orbit (LEO) atomic oxygen were measured on a variety of spacecraft materials which obtained exposure on STS-5. Material degradation dependency on temperature was found in one material. Of the five paints flown, only S13GLO was unaffected. Generally, the glossy paints became Lambertian and the diffuse coatings improved. Scanning electron microscope examinations indicated removal of urethane and epoxy paint binder materials. Reaction products were evident on the surfaces of Z302 paint and Mylar. Thin films showed thickness losses ranging from negligible loss in Teflon to considerable loss in Mylar and Kapton. Glossy films such as black Kapton and white Tedlar became diffused. Kevlar 29 rope lost tensile strength and silver solar cell interconnect material oxidized. Oxidation on the backside of an elevated specimen indicated that reflections of oxygen atoms were occurring and that reflecting surfaces, probably Kapton, were not fully accommodating the incident atoms.

  15. NOAA 26.5 Ah LEO characterization test

    NASA Technical Reports Server (NTRS)

    Morrow, G. W.

    1986-01-01

    The General Electric (GE) 26.5 Ah NOAA-G flight nickel-cadmium cells were obtained from RCA-Astro Electronics to undergo performance characterization testing at the Goddard Space Flight Center (GSFC). This lot of cells was manufactured with passivated positive plate, to control nickel structure attack duing active material impregnation, and less electrolyte than normal (less than 3cc/Ah). The cells were tested in a parametric low Earth orbit (LEO) cycling regime that was previously used to test and characterize standard 50 Ah cells. Life cycle testing at the Naval Weapons Support Center (NWSC), in Crane, followed. The results of the test showed nominal performance in comparison with previous test data on the standard 50. Life cycle testing in the NOAA orbital regime is continuing at NWSC.

  16. Semianalytic Theory of Motion for LEO Satellites Under Air Drag

    NASA Astrophysics Data System (ADS)

    Bezdek, A.

    The presented semianalytic theory focuses on the longterm evolution of the LEO satellites motion, with the TD/TD88 model of the total density as a key ingredient. Besides, the theory takes into account the main geopotential perturbations, for satellites with low eccentricity and/or inclination, nonsingular elements are used. An interesting feature of the theory is its computational speed (e.g. the 10-year propagation takes 5.5 s on a PC with Intel Celeron 1.7 GHz), while considering major physical conditions that strongly influence the thermospheric density (solar flux, geomagnetic activity, diurnal and seasonal variations, geographic latitude). The online calculation as well as the code are available on the Internet. The theory has been tested against the real world data of several spherical satellites. For the lifetime prediction accuracy estimate of the theory, we used a confidential interval based on the uncertainty in the drag coefficient CD, while taking the measured values of the solar flux and geomagnetic index. The modelled long-term behaviour of the orbital elements is in reasonably good agreement with the data, the computed lifetimes fall within the CD-induced confidential intervals, typical error in the mean lifetime prediction being a few percent. The tests showed that - provided one appropriately models the solar and geomagnetic activity - the theory may be used in the areas where one needs a quick orbital propagator for LEO objects influenced by air drag (mission planning, lifetime prediction, space debris dynamics). As an example, we will show the mission planning and the medium-term prediction of the motion for the MIMOSA satellite.

  17. An all electronic transportation system from LEO to GEO and beyond

    NASA Technical Reports Server (NTRS)

    Brown, William C.

    1989-01-01

    System description and moon mission interface; LEO to GEO flight times; technology readiness and modular construction; system capacity and costs; and reduction of propellant mass are outlined. This presentation is represented by viewgraph only.

  18. NEW EMPLOYEE ON THE JOB - LEO C FRANCISCUS MISSIONS ANALYSIS BRANCH WORKING ON RECOVERABLE BOOSTERS

    NASA Technical Reports Server (NTRS)

    1963-01-01

    NEW EMPLOYEE ON THE JOB - LEO C FRANCISCUS MISSIONS ANALYSIS BRANCH WORKING ON RECOVERABLE BOOSTERS - PERFORM MISSION ANALYSIS STUDIES - AT PRESENT TIME STUDYING SUBSONIC AND SUPERSONIC COMBUSTION RAM JET ENGINES - ALSO PERFORMING ANALYTICAL STUDIES

  19. Celebrating Diversity through Children's Literature: An Interview with Leo and Diane Dillon.

    ERIC Educational Resources Information Center

    Pavonetti, Linda

    2001-01-01

    Presents an interview with the illustrators Leo and Diane Dillon. Concludes that they hope their illustrations will bring to children a feeling of pride and understanding that they are all important and are all part of one world. (SG)

  20. Seismic amplitude anomalies associated with thick First Leo sandstone lenses, eastern Powder River basin, Wyoming.

    USGS Publications Warehouse

    Balch, A.H.; Lee, M.W.; Miller, J.J.; Ryder, R.T.

    1981-01-01

    Several new discoveries of oil production in the Leo sandstone, an economic unit in the Pennsylvanian middle member of the Minnelusa formation, eastern Powder River basin, Wyoming-Nebraska-South Dakota, have renewed exploration interest in this area. Vertical seismic profiles (VSP) and model studies suggested that a measurable seismic amplitude anomaly is frequently associated with the thick First Leo sandstone lenses. To test this concept, a surface reflection seismic profile was run between two wells about 12 miles apart. The First Leo was present and productive in one well and thin and barren in the other. The surface profile shows the predicted amplitude anomaly at the well where a thick lens is known to exist. Two other First Leo amplitude anomalies also appear on the surface seismic profile between the two wells, which may indicate the presence of additional lenses.-Authors

  1. AGB stars in Leo P and their use as metallicity probes

    NASA Astrophysics Data System (ADS)

    Lee ( ), Chien-Hsiu

    2016-09-01

    Leo P is the most metal-poor yet star-forming galaxy in the local volume, and has the potential to serve as a local counterpart to interpret the properties of distant galaxies in the early universe. We present a comprehensive search of asymptotic giant branch (AGB) stars in Leo P using deep infrared imaging. AGB stars are the major dust contributors; the metal poor nature of Leo P can help to shed light on the dust formation process in very low-metallicity environments, similar to the early Universe. We select and classify oxygen-rich and carbon-rich candidate AGB stars using J - K versus K colour-magnitude diagram. To filter out contaminations from background galaxies, we exploit the high-resolution Hubble Space Telescope imaging and identify 9 oxygen-rich AGBs and 13 carbon-rich AGB stars in Leo P. We then use the ratio of carbon-rich and oxygen-rich AGB stars (C/M ratio) as an indicator of on-site metallicity and derive the global metallicity [Fe/H] = -1.8 dex for Leo P, in good agreement with previous studies using isochrone fitting. Follow-up observations of these Leo P AGB stars in the mid-infrared [e.g. Spitzer, James Webb Space Telescope (JWST)] will be invaluable to measure the dust formation rates using Spectral energy distribution (SED) fitting.

  2. The Many Worlds of Leo Szilard: Physicist, Peacemaker, Provocateur

    NASA Astrophysics Data System (ADS)

    Lanouette, William

    2014-03-01

    Best known for being the first to conceive and patent the nuclear chain reaction in the 1930s, Leo Szilard should also be remembered for other insights in both physics and biology, and for historical initiatives to control the A-bomb he helped create. In physics, Szilard applied entropy to data in a seminal 1929 paper that laid the basis for ``information theory.'' Szilard co-designed an electromagnetic refrigerator pump with Einstein in the 1920s, in 1939 he co-designed the first nuclear reactor with Enrico Fermi, and he later thought up and named the nuclear ``breeder'' reactor. Biologist Francois Jacob called Szilard an ``intellectual bumblebee'' for the many novel ideas he shared, including one that earned Jacob and others the Nobel Prize. James D. Watson said that for intellectual stimulation he liked being around Szilard because ``Leo got excited about something before it was true.'' A political activist, Szilard proposed and drafted the 1939 letter Einstein sent to President Franklin Roosevelt that warned of German A-bomb work and led to the Manhattan Project - where Szilard was ``Chief Physicist.'' Yet Szilard then worked tirelessly to curb nuclear weapons, organizing a scientists' petition to President Truman and lobbying Congress for civilian control of the atom. Szilard loved dreaming up new institutions. He helped to create the Pugwash Conferences on Science and World Affairs, and founded the Council for a Livable World - the first political action committee for arms control. In biology, Szilard proposed the European Molecular Biology Organization modeled on CERN, and helped create the Salk Institute for Biological Studies, where he was one of the first fellows. Shy, witty, and eccentric, Szilard wrote a political satire in 1960 that predicted when the US-Soviet nuclear arms race would end in the late 1980s. Another satire, ``My Trial as a War Criminal'' about scientists' responsibilities for weapons of mass destruction, is credited with prompting

  3. Robust and precise baseline determination of distributed spacecraft in LEO

    NASA Astrophysics Data System (ADS)

    Allende-Alba, Gerardo; Montenbruck, Oliver

    2016-01-01

    Recent experience with prominent formation flying missions in Low Earth Orbit (LEO), such as GRACE and TanDEM-X, has shown the feasibility of precise relative navigation at millimeter and sub-millimeter levels using GPS carrier phase measurements with fixed integer ambiguities. However, the robustness and availability of the solutions provided by current algorithms may be highly dependent on the mission profile. The main challenges faced in the LEO scenario are the resulting short continuous carrier phase tracking arcs along with the observed rapidly changing ionospheric conditions, which in the particular situation of long baselines increase the difficulty of correct integer ambiguity resolution. To reduce the impact of these factors, the present study proposes a strategy based on a reduced-dynamics filtering of dual-frequency GPS measurements for precise baseline determination along with a dedicated scheme for integer ambiguity resolution, consisting of a hybrid sequential/batch algorithm based on the maximum a posteriori and integer aperture estimators. The algorithms have been tested using flight data from the GRACE, TanDEM-X and Swarm missions in order to assess their robustness to different formation and baseline configurations. Results with the GRACE mission show an average 0.7 mm consistency with the K/Ka-band ranging measurements over a period of more than two years in a baseline configuration of 220 km. Results with TanDEM-X data show an average of 3.8 mm consistency of kinematic and reduced-dynamic solutions in the along-track component over a period of 40 days in baseline configurations of 500 m and 75 km. Data from Swarm A and Swarm C spacecraft are largely affected by atmospheric scintillation and contain half cycle ambiguities. The results obtained under such conditions show an overall consistency between kinematic and reduced-dynamic solutions of 1.7 cm in the along-track component over a period of 30 days in a variable baseline of approximately 60

  4. BabeLO--An Extensible Converter of Programming Exercises Formats

    ERIC Educational Resources Information Center

    Queiros, R.; Leal, J. P.

    2013-01-01

    In the last two decades, there was a proliferation of programming exercise formats that hinders interoperability in automatic assessment. In the lack of a widely accepted standard, a pragmatic solution is to convert content among the existing formats. BabeLO is a programming exercise converter providing services to a network of heterogeneous…

  5. THE SPACE MOTION OF LEO I: HUBBLE SPACE TELESCOPE PROPER MOTION AND IMPLIED ORBIT

    SciTech Connect

    Sohn, Sangmo Tony; Van der Marel, Roeland P.; Besla, Gurtina; Boylan-Kolchin, Michael; Bullock, James S.; Majewski, Steven R.

    2013-05-10

    We present the first absolute proper motion measurement of Leo I, based on two epochs of Hubble Space Telescope ACS/WFC images separated by {approx}5 years in time. The average shift of Leo I stars with respect to {approx}100 background galaxies implies a proper motion of ({mu}{sub W}, {mu}{sub N}) = (0.1140 {+-} 0.0295, -0.1256 {+-} 0.0293) mas yr{sup -1}. The implied Galactocentric velocity vector, corrected for the reflex motion of the Sun, has radial and tangential components V{sub rad} = 167.9 {+-} 2.8 km s{sup -1} and V{sub tan} = 101.0 {+-} 34.4 km s{sup -1}, respectively. We study the detailed orbital history of Leo I by solving its equations of motion backward in time for a range of plausible mass models for the Milky Way (MW) and its surrounding galaxies. Leo I entered the MW virial radius 2.33 {+-} 0.21 Gyr ago, most likely on its first infall. It had a pericentric approach 1.05 {+-} 0.09 Gyr ago at a Galactocentric distance of 91 {+-} 36 kpc. We associate these timescales with characteristic timescales in Leo I's star formation history, which shows an enhanced star formation activity {approx}2 Gyr ago and quenching {approx}1 Gyr ago. There is no indication from our calculations that other galaxies have significantly influenced Leo I's orbit, although there is a small probability that it may have interacted with either Ursa Minor or Leo II within the last {approx}1 Gyr. For most plausible MW masses, the observed velocity implies that Leo I is bound to the MW. However, it may not be appropriate to include it in models of the MW satellite population that assume dynamical equilibrium, given its recent infall. Solution of the complete (non-radial) timing equations for the Leo I orbit implies an MW mass M{sub MW,vir} = 3.15{sub -1.36}{sup +1.58} x 10{sup 12} M{sub Sun }, with the large uncertainty dominated by cosmic scatter. In a companion paper, we compare the new observations to the properties of Leo I subhalo analogs extracted from cosmological

  6. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight cells. An update

    NASA Technical Reports Server (NTRS)

    Smithrick, John J.; Hall, Stephen W.

    1991-01-01

    An update of validation test results confirming the breakthrough in LEO cycle life of nickel-hydrogen cells containing 26 percent potassium hydroxide (KOH) electrolyte is presented. A breakthrough in the LEO cycle life of individual pressure vessel nickel-hydrogen cells is reported. The cycle life of boiler plate cells containing 26 percent KOH electrolyte was about 40,000 LEO cycles compared to 3500 cycles for cells containing 31 percent KOH.

  7. A SEARCH FOR DUST EMISSION IN THE LEO INTERGALACTIC CLOUD

    SciTech Connect

    Bot, Caroline; Helou, George; Puget, Jeremie; Latter, William B.; Schneider, Stephen; Terzian, Yervant

    2009-08-15

    We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with the InfraRed Array Camera and the Multiband Imaging Photometer for Spitzer on the Spitzer Space Telescope. Our analysis of these maps is done at each wavelength relative to the H I spatial distribution. We observe a probable detection at 8 {mu}m and a marginal detection at 24 {mu}m associated with the highest H I column densities in the cloud. At 70 and 160 {mu}m, upper limits on the dust emission are deduced. The level of the detection is low so that the possibility of a fortuitous cirrus clump or of an overdensity of extragalactic sources along the line of sight cannot be excluded. If this detection is confirmed, the quantities of dust inferred imply a dust-to-gas ratio in the intergalactic cloud up to a few times solar but no less than 1/20 solar. A confirmed detection would therefore exclude the possibility that the intergalactic cloud has a primordial origin. Instead, this large intergalactic cloud could therefore have been formed through interactions between galaxies in the group.

  8. A metapopulation approach to African lion (Panthera leo) conservation.

    PubMed

    Dolrenry, Stephanie; Stenglein, Jennifer; Hazzah, Leela; Lutz, R Scott; Frank, Laurence

    2014-01-01

    Due to anthropogenic pressures, African lion (Panthera leo) populations in Kenya and Tanzania are increasingly limited to fragmented populations. Lions living on isolated habitat patches exist in a matrix of less-preferred habitat. A framework of habitat patches within a less-suitable matrix describes a metapopulation. Metapopulation analysis can provide insight into the dynamics of each population patch in reference to the system as a whole, and these analyses often guide conservation planning. We present the first metapopulation analysis of African lions. We use a spatially-realistic model to investigate how sex-biased dispersal abilities of lions affect patch occupancy and also examine whether human densities surrounding the remaining lion populations affect the metapopulation as a whole. Our results indicate that male lion dispersal ability strongly contributes to population connectivity while the lesser dispersal ability of females could be a limiting factor. When populations go extinct, recolonization will not occur if distances between patches exceed female dispersal ability or if females are not able to survive moving across the matrix. This has profound implications for the overall metapopulation; the female models showed an intrinsic extinction rate from five-fold to a hundred-fold higher than the male models. Patch isolation is a consideration for even the largest lion populations. As lion populations continue to decline and with local extinctions occurring, female dispersal ability and the proximity to the nearest lion population are serious considerations for the recolonization of individual populations and for broader conservation efforts.

  9. Detection of starquakes on the red dwarf AD Leo

    NASA Astrophysics Data System (ADS)

    Contadakis, M. E.; Avgoloupis, S. J.; Seiradakis, J. H.; Papantoniou, Ch.

    2016-07-01

    The results of the analysis of the one color (B) observations of the Stefanion Observatory for the red dwarf AD Leo at any stage of the stellar activity (quiescence, weak flares, strong flares),indicate that: (1) Transient high frequency oscillations occur during the flare event and during the quiet-star phase as well; (2) The Observed frequencies range between 0.0005Hz (period 33min) and 0.3 Hz (period 3s) not rigorously bounded; However, the quiescence parts of the light-curve which were analyzed belong to the pre- or after- flare state i.e. are connected with a major magnetic even (the observed flare). In this work we find that transient oscillations appear far apart from the observed flares, during the quiet state of the stars, as a result of the general magnetic activity of the star. The power spectrum of these oscillations resembles that of the solar like oscillation spectra i.e the sunquakes spectra. Finally a tentative estimation of the main physical parameters of the star, using asteroseismic analysis, was performed.

  10. Arcing in LEO: Does the Whole Array Discharge?

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T.; Hillard, G. Barry

    2005-01-01

    The conventional wisdom about solar array arcing in LEO is that only the parts of the solar array that are swept over by the arc-generated plasma front are discharged in the initial arc. This limits the amount of energy that can be discharged. Recent work done at the NASA Glenn Research Center has shown that this idea is mistaken. In fact, the capacitance of the entire solar array may be discharged, which for large arrays leads to very large and possibly debilitating arcs, even if no sustained arc occurs. We present the laboratory work that conclusively demonstrates this fact by using a grounded plate that prevents the arc-plasma front from reaching certain array strings. Finally, we discuss the dependence of arc strength and arc pulse width on the capacitance that is discharged, and provide a physical mechanism for discharge of the entire array, even when parts of the array are not accessible to the arc-plasma front. Mitigation techniques are also presented.

  11. Arcing in LEO - Does the Whole Array Discharge?

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T.; Hillard, G. Barry

    2005-01-01

    The conventional wisdom about solar array arcing in LEO is that only the parts the solar array that are swept over by the arc-generated plasma front are discharged in the initial arc. This limits the amount of energy that can be discharged. Recent work done at the NASA Glenn Research Center has shown that this idea is mistaken. In fact, the capacitance of the entire solar array may be discharged, which for large arrays leads to very large and possibly debilitating arcs, even if no sustained arc occurs. We present the laboratory work that conclusively demonstrates this fact by using a grounded plate that prevents the arc-plasma front from reaching certain array strings. Finally, we discuss the dependence of arc strength and arc pulse width on the capacitance that is discharged, and provide a physical mechanism for discharge of the entire array, even when parts of the array are not accessible to the arc-plasma front. Mitigation techniques are also presented.

  12. THE STAR FORMATION HISTORY OF LEO T FROM HUBBLE SPACE TELESCOPE IMAGING

    SciTech Connect

    Weisz, Daniel R.; Dalcanton, Julianne J.; Gilbert, Karoline M.; Williams, Benjamin F.; Zucker, Daniel B.; Dolphin, Andrew E.; Martin, Nicolas F.; De Jong, Jelte T. A.; Holtzman, Jon A.; Bell, Eric F.; Belokurov, Vasily; Evans, N. Wyn

    2012-04-01

    We present the star formation history (SFH) of the faintest known star-forming galaxy, Leo T, based on deep imaging taken with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2). The HST/WFPC2 color-magnitude diagram (CMD) of Leo T is exquisitely deep, extending {approx}2 mag below the oldest main-sequence turnoff, permitting excellent constraints on star formation at all ages. We use a maximum likelihood CMD fitting technique to measure the SFH of Leo T assuming three different sets of stellar evolution models: Padova (solar-scaled metallicity) and BaSTI (both solar-scaled and {alpha}-enhanced metallicities). The resulting SFHs are remarkably consistent at all ages, indicating that our derived SFH is robust to the choice of stellar evolution model. From the lifetime SFH of Leo T, we find that 50% of the total stellar mass formed prior to z {approx} 1 (7.6 Gyr ago). Subsequent to this epoch, the SFH of Leo T is roughly constant until the most recent {approx}25 Myr, where the SFH shows an abrupt drop. This decrease could be due to a cessation of star formation or stellar initial mass function sampling effects, but we are unable to distinguish between the two scenarios. Overall, our measured SFH is consistent with previously derived SFHs of Leo T. However, the HST-based solution provides improved age resolution and reduced uncertainties at all epochs. The SFH, baryonic gas fraction, and location of Leo T are unlike any of the other recently discovered faint dwarf galaxies in the Local Group, and instead bear strong resemblance to gas-rich dwarf galaxies (irregular or transition), suggesting that gas-rich dwarf galaxies may share common modes of star formation over a large range of stellar mass ({approx}10{sup 5}-10{sup 9} M{sub Sun }).

  13. Study of LEO-SAT microwave link for broad-band mobile satellite communication system

    NASA Technical Reports Server (NTRS)

    Fujise, Masayuki; Chujo, Wataru; Chiba, Isamu; Furuhama, Yoji; Kawabata, Kazuaki; Konishi, Yoshihiko

    1993-01-01

    In the field of mobile satellite communications, a system based on low-earth-orbit satellites (LEO-SAT's) such as the Iridium system has been proposed. The LEO-SAT system is able to offer mobile telecommunication services in high-latitude areas. Rain degradation, fading and shadowing are also expected to be decreased when the system is operated at a high elevation angle. Furthermore, the propagation delay generated in the LEO-SAT system is less pronounced than that in the geostationary orbit satellite (GEO-SAT) system and, in voice services, the effect of the delay is almost negligible. We proposed a concept of a broad-band mobile satellite communication system with LEO-SAT's and Optical ISL. In that system, a fixed L-band (1.6/1.5 GHz) multibeam is used to offer narrow band service to the mobile terminals in the entire area covered by a LEO-SAT and steerable Ka-band (30/20 GHz) spot beams are used for the wide band service. In this paper, we present results of a study of LEO-SAT microwave link between a satellite and a mobile terminal for a broad-band mobile satellite communication system. First, the results of link budget calculations are presented and the antennas mounted on satellites are shown. For a future mobile antenna technology, we also show digital beamforming (DBF) techniques. DBF, together with modulation and/or demodulation, is becoming a key technique for mobile antennas with advanced functions such as antenna pattern calibration, correction, and radio interference suppression. In this paper, efficient DBF techniques for transmitting and receiving are presented. Furthermore, an adaptive array antenna system suitable for this LEO-SAT is presented.

  14. 77 FR 2715 - D'Lo Gas Storage, LLC; Notice of Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-19

    ... Energy Regulatory Commission D'Lo Gas Storage, LLC; Notice of Application Take notice that on December 29, 2011, D'Lo Gas Storage, LLC (D'Lo), 1002 East St. Mary Blvd., Lafayette, Louisiana 70503, filed in... D'Lo to construct, operate, and maintain a new natural gas storage project to be located in...

  15. Low-Earth-Orbiter resource allocation and capacity planning for the DSN using LEO4CAST

    NASA Technical Reports Server (NTRS)

    Fox, G.; Borden, C.

    1994-01-01

    The Deep Space Network provides tracking and communication services for a number of U.S. and international low-Earth-orbiting (LEO) and near-Earth missions. This service is supplied by the 26-m subnet (located at each of the DSN complexes), the 9-m and the 34-m Antenna Research System antennas at Goldstone, and the 11-m antennas (following the orbital VLBI mission). An increasing number of LEO missions are planned for DSN support, which will result in increasingly complex ground resource allocation and mission support trades. To support TDA decision making on mission support and cost-effective ground system evolution for this 26-m subnet, LEO4CAST has been developed. LEO4CAST is a tool that uses statistical approaches to provide useful information for long-term ground system capacity planning and near-term resource allocation (prior to detailed time-of-day scheduling). LEO4CAST is currently beta-test software and is being exercised by both the Office of Telecommunications and Data Acquisition (TDA) and the JPL Systems Division.

  16. The effect of solar forcing induced atmospheric perturbations on LEO satellites' nominal aerodynamic drag

    NASA Astrophysics Data System (ADS)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar; Weigel, Robert

    2016-07-01

    Atmospheric drag is the strongest force perturbing the motion of satellites in low Earth orbits LEO, and could cause re-entry of satellites, difficulty in identifying and tracking of the satellites and other space objects, manuvering and prediction of lifetime and re-entry. Solar activities influence the temperature, density and composition of the upper atmosphere. These effects thus strongly depend on the phase of a solar cycle. The frequency of intense flares and storms increase during solar maximum. Heating up of the atmosphere causes its expansion eventually leading to accelerated drag of orbiting satellites, especially those in LEO. In this paper, we present the model of the atmospheric drag effect on the trajectory of hypothetical LEO satellites of different ballistic coefficients. We investigate long-term trend of atmospheric drag on LEO satellites due to solar forcing induced atmospheric perturbations and heating at different phases of the solar cycle, and during interval of strong geomagnetic disturbances or storms. We show the dependence of orbital decay on severity of both the solar cycle and phase, and the extent of geomagnetic perturbations. The result of the model compares well with the observed decay profile of existing LEO satellites and provides a better understanding of the issue of the orbital decay. Our result may also be useful for selection of launch window of satellites for an extended lifetime in the orbit.

  17. Water vapor retrieval by LEO and GEO SAR: techniques and performance evaluation.

    NASA Astrophysics Data System (ADS)

    Fermi, Alessandro; Silvio Marzano, Frank; Monti Guarnieri, Andrea; Pierdicca, Nazzareno; Realini, Eugenio; Venuti, Giovanna

    2016-04-01

    The millimetric sensitivity of SAR interferometry has been proved fruitful in estimating water-vapor maps, that can then be processed into higher level ZWD and PWV products. In the paper, we consider two different SAR surveys: Low Earth Orbiting (LEO) SAR, like ESA Sentinel-1, and Geosynchronous Earth Orbiting SAR. The two system are complementary, where LEO coverage is world-wide, while GEO is regional. On the other hand, LEO revisit is daily-to weekly, whereas GEO provides images in minutes to hours. Finally, LEO synthetic aperture is so short, less than a second, that the water-vapor is mostly frozen, whereas in the long GEO aperture the atmospheric phase screen would introduce a total decorrelation, if not compensated for. In the paper, we first review the Differential Interferometric techniques to get differential delay maps - to be then converted into water-vapor products, and then evaluate the quality in terms of geometric resolution, sensitivity, percentage of scene coverage, revisit, by referring to L and C band system, for both LEO and GEO. Finally, we discuss an empirical model for time-space variogram, and show a preliminary validation by campaign conducted with Ground Based Radar, as a proxy of GEO-SAR, capable of continuous scanning wide areas (up to 15 km) with metric resolution.

  18. The Elusive Old Population of the Dwarf Spheroidal Galaxy Leo I.

    PubMed

    Held; Saviane; Momany; Carraro

    2000-02-20

    We report the discovery of a significant old population in the dwarf spheroidal (dSph) galaxy Leo I as a result of a wide-area search with the ESO New Technology Telescope. Studies of the stellar content of Local Group dwarf galaxies have shown the presence of an old stellar population in almost all of the dwarf spheroidal galaxies. The only exception was Leo I, which alone appeared to have delayed its initial star formation episode until just a few gigayears ago. The color-magnitude diagram of Leo I now reveals an extended horizontal branch, unambiguously indicating the presence of an old, metal-poor population in the outer regions of this galaxy. Yet we find little evidence for a stellar population gradient, at least outside R>2' (0.16 kpc), since the old horizontal branch stars of Leo I are radially distributed as their more numerous intermediate-age helium-burning counterparts. The discovery of a definitely old population in the predominantly young dwarf spheroidal galaxy Leo I points to a sharply defined first epoch of star formation common to all of the Local Group dSph galaxies as well as to the halo of the Milky Way.

  19. Faster than fiber: Advantages and challenges of LEO communications satellite systems

    NASA Astrophysics Data System (ADS)

    Campanella, S. Joseph; Kirkwood, Timothy J.

    1995-01-01

    Low Earth Orbit (LEO) communications satellite systems are emerging as attractive alternatives to the Geostationary Earth Orbit (GEO) systems. GEO satellites have largely dominated the commercial and government communications satellite systems for telecommunications services since the early 1960's. A principal driver behind the move to LEO satellites is the competition to long propagation delay geostationary orbit satellite systems created by rapid expansion of short propagation delay terrestrial land and undersea fiber optic cable links for national and global connectivity. Communication paths over LEO satellites can have shorter propagation delay than terrestrial fiber. This is because the speed of electromagnetic wave propagation via LEO satellites is 50% greater than that of light in fiber optic cable. This fact eliminates the long propagation delay property that has become synonymous with GEO communications satellite systems. Other drivers are the use of small portable and hand-held earth terminals and the promise of lower launch cost of small satellites to low earth orbits. The paper expands on the properties that promise to make LEO communications satellite systems the choice of the future.

  20. An Assessment of the Current LEO Debris Environment and the Need for Active Debris Removal

    NASA Technical Reports Server (NTRS)

    Liou, Jer-Chyi

    2010-01-01

    The anti-satellite test on the Fengun-1 C weather satellite in early 2007 and the collision between Iridium 33 and Cosmos 2251 in 2009 dramatically altered the landscape of the human-made orbital debris environment in the low Earth orbit (LEO). The two events generated approximately 5500 fragments large enough to be tracked by the U.S. Space Surveillance Network. Those fragments account for more than 60% increase to the debris population in LEO. However, even before the ASAT test, model analyses already indicated that the debris population (for those larger than 10 cm) in LEO had reached a point where the population would continue to increase, due to collisions among existing objects, even without any future launches. The conclusion implies that as satellites continue to be launched and unexpected breakup events continue to occur, commonly-adopted mitigation measures will not be able to stop the collision-driven population growth. To remediate the debris environment in LEO, active debris removal must be considered. This presentation will provide an updated assessment of the debris environment after the Iridium 33/Cosmos 2251 collision, an analysis of several future environment projections based on different scenarios, and a projection of collision activities in LEO in the near future. The need to use active debris removal to stabilize future debris environment will be demonstrated and the effectiveness of various active debris removal strategies will be quantified.

  1. Quadrature mixture LO suppression via DSW DAC noise dither

    DOEpatents

    Dubbert, Dale F.; Dudley, Peter A.

    2007-08-21

    A Quadrature Error Corrected Digital Waveform Synthesizer (QECDWS) employs frequency dependent phase error corrections to, in effect, pre-distort the phase characteristic of the chirp to compensate for the frequency dependent phase nonlinearity of the RF and microwave subsystem. In addition, the QECDWS can employ frequency dependent correction vectors to the quadrature amplitude and phase of the synthesized output. The quadrature corrections cancel the radars' quadrature upconverter (mixer) errors to null the unwanted spectral image. A result is the direct generation of an RF waveform, which has a theoretical chirp bandwidth equal to the QECDWS clock frequency (1 to 1.2 GHz) with the high Spurious Free Dynamic Range (SFDR) necessary for high dynamic range radar systems such as SAR. To correct for the problematic upconverter local oscillator (LO) leakage, precision DC offsets can be applied over the chirped pulse using a pseudo-random noise dither. The present dither technique can effectively produce a quadrature DC bias which has the precision required to adequately suppress the LO leakage. A calibration technique can be employed to calculate both the quadrature correction vectors and the LO-nulling DC offsets using the radar built-in test capability.

  2. The ClearfLo project - Understanding London's meteorology and composition

    NASA Astrophysics Data System (ADS)

    Belcher, Stephen; Bohnenstengel, Sylvia

    2014-05-01

    ClearfLo is a large multi-institutional project funded by the UK Natural Environment Research Council (NERC). ClearfLo established integrated measurements of meteorology, gaseous and particulate composition/loading of London's (UK) urban atmosphere in 2011 and 2012 to understand the processes underlying poor air quality. A new and unique long-term measurement infrastructure was established in London at street level, urban background and elevated sites and contrasted against rural locations to determine the urban increment in meteorology and pollution. This approach enables understanding the seasonal variations in the meteorology and composition together with the controlling processes. In addition two intensive observation periods (IOPs) provide more detail in winter 2012 and during the Olympics in summer 2012 focusing upon the vertical structure and evolution of the urban boundary layer, chemical controls on nitrogen dioxide and ozone production, in particular the role of volatile organic compounds, and processes controlling the evolution, size, distribution and composition of particulate matter. In this talk we present early analysis of the meteorology and air quality measurements within ClearfLo. In particular we show measurements that indicate the dominant regimes of London's boundary layer.

  3. Handover aspects for a Low Earth Orbit (LEO) CDMA Land Mobile Satellite (LMS) system

    NASA Technical Reports Server (NTRS)

    Carter, P.; Beach, M. A.

    1993-01-01

    This paper addresses the problem of handoff in a land mobile satellite (LMS) system between adjacent satellites in a low earth orbit (LEO) constellation. In particular, emphasis is placed on the application of soft handoff in a direct sequence code division multiple access (DS-CDMA) LMS system. Soft handoff is explained in terms of terrestrial macroscopic diversity, in which signals transmitted via several independent fading paths are combined to enhance the link quality. This concept is then reconsidered in the context of a LEO LMS system. A two-state Markov channel model is used to simulate the effects of shadowing on the communications path from the mobile to each satellite during handoff. The results of the channel simulation form a platform for discussion regarding soft handoff, highlighting the potential merits of the scheme when applied in a LEO LMS environment.

  4. GEO vs. LEO Space Telecommunication Systems Commercial Set Up, Finance &Economics

    NASA Astrophysics Data System (ADS)

    Kreisel, Joerg

    2002-01-01

    Space-based commercial telecommunication systems - especially in GEO - still represent the big volume segment in commercial space and probably will do so for a while. Although such end-to-end systems both in GEO and LEO are using satellites, ground stations, and service centers, etc., their commercial genesis differs significantly. Based on existing and planned space telecommunication businesses, this paper deals with prime characteristics of commercial GEO and LEO systems and their differences. In a tutorial way the stages of development of both LEO- and GEO-type business ventures are presented. The entire commercial development path is covered (concept, business plan, financing, partnership, growth, etc.). Focus is to understand what drives space telecommunication business and what it takes to start such new commercial space ventures. The perspective given is also based on the author's longstanding background in space commercialization and experiences made as a venture capitalist.

  5. Materials selection for long life in LEO: A critical evaluation of atomic oxygen testing with thermal atom systems

    NASA Technical Reports Server (NTRS)

    Koontz, S. L.; Kuminecz, J.; Leger, L.; Nordine, P.

    1988-01-01

    The use of thermal atom test methods as a materials selection and screening technique for low-Earth orbit (LEO) spacecraft is critically evaluated. The chemistry and physics of thermal atom environments are compared with the LEO environment. The relative reactivities of a number of materials determined to be in thermal atom environments are compared to those observed in LEO and in high quality LEO simulations. Reaction efficiencies measured in a new type of thermal atom apparatus are one-hundredth to one-thousandth those observed in LEO, and many materials showing nearly identical reactivities in LEO show relative reactivities differing by as much as a factor of 8 in thermal atom systems. A simple phenomenological kinetic model for the reaction of oxygen atoms with organic materials can be used to explain the differences in reactivity in different environments. Certain specific thermal test environments can be used as reliable materials screening tools. Using thermal atom methods to predict material lifetime in LEO requires direct calibration of the method against LEO data or high quality simulation data for each material.

  6. 20 CFR 10.735 - When is a non-Federal law enforcement officer (LEO) covered under the FECA?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false When is a non-Federal law enforcement officer (LEO) covered under the FECA? 10.735 Section 10.735 Employees' Benefits OFFICE OF WORKERS' COMPENSATION... When is a non-Federal law enforcement officer (LEO) covered under the FECA? (a) A law...

  7. New U-Pb SHRIMP dating for the Leo Pargil gneiss dome, western Himalaya

    NASA Astrophysics Data System (ADS)

    Leech, M. L.; Sas, R.

    2006-12-01

    The Leo Pargil gneiss dome is comprised of upper amphibolite-facies metasedimentary rocks of the lower Tethyan Himalayan sequence (the Haimantas unit) that are intruded by numerous small granitoid bodies and leucogranite dikes. The dome is exposed in northern India/southwestern Tibet at the confluence of the Sutlej and Spiti rivers west of the Zada basin. The dome is bound by generally N-S trending normal faults; the western boundary is termed the Kaurik-Chango normal fault and has a history of recent seismicity. The Leo Pargil dome differs from other North Himalayan domes in that it exhibits orogen-parallel stretching lineations and a uniform top-to-the-northwest sense-of-shear on its western flank (in contrast to approximately arc-normal stretching lineations and variable sense-of-shear in other North Himalayan domes; the youngest phase of Leo Pargil dome development is related to an orogen-parallel extensional structure similar to that which bounds the Gurla Mandhata dome to the southeast. New U-Pb SHRIMP dating of zircon yields Late Archean to Late Proterozoic ages for Leo Pargil paragneisses (c. 800-900 Ma and rarer 2-3 Ga zircons) and Late Oligocene to Early Miocene ages for granitoid intrusions (c. 27-16 Ma). These Oligocene to Miocene ages for Leo Pargil granitoids may correspond to magmatism associated with the widespread leucogranite bodies exposed througout the Himalaya. The Leo Pargil dome, like other similar Himalayan gneiss domes, may be exposures of a ductile mid-crustal channel.

  8. THE SPACE MOTION OF LEO I: THE MASS OF THE MILKY WAY'S DARK MATTER HALO

    SciTech Connect

    Boylan-Kolchin, Michael; Bullock, James S.; Sohn, Sangmo Tony; Van der Marel, Roeland P.; Besla, Gurtina

    2013-05-10

    We combine our Hubble Space Telescope measurement of the proper motion of the Leo I dwarf spheroidal galaxy (presented in a companion paper) with the highest resolution numerical simulations of Galaxy-size dark matter halos in existence to constrain the mass of the Milky Way's dark matter halo (M{sub vir,MW}). Despite Leo I's large Galactocentric space velocity (200 km s{sup -1}) and distance (261 kpc), we show that it is extremely unlikely to be unbound if Galactic satellites are associated with dark matter substructure, as 99.9% of subhalos in the simulations are bound to their host. The observed position and velocity of Leo I strongly disfavor a low-mass Milky Way: if we assume that Leo I is the least bound of the Milky Way's classical satellites, then we find that M{sub vir,MW} > 10{sup 12} M{sub Sun} at 95% confidence for a variety of Bayesian priors on M{sub vir,MW}. In lower mass halos, it is vanishingly rare to find subhalos at 261 kpc moving as fast as Leo I. Should an additional classical satellite be found to be less bound than Leo I, this lower limit on M{sub vir,MW} would increase by 30%. Imposing a mass-weighted {Lambda}CDM prior, we find a median Milky Way virial mass of M{sub vir,MW} = 1.6 Multiplication-Sign 10{sup 12} M{sub Sun }, with a 90% confidence interval of [1.0-2.4] Multiplication-Sign 10{sup 12} M{sub Sun }. We also confirm a strong correlation between subhalo infall time and orbital energy in the simulations and show that proper motions can aid significantly in interpreting the infall times and orbital histories of satellites.

  9. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight battery cells

    NASA Technical Reports Server (NTRS)

    Smithrick, John J.; Hall, Stephen W.

    1990-01-01

    A breakthrough in low earth orbit (LEO) cycle life of individual pressure vessel (IPV) nickel hydrogen battery cells was reported. The cycle life of boiler plate cells containing 26 percent potassium hydroxide (KOH) electrolyte was about 40,000 LEO cycles compared to 3500 cycles for cells containing 31 percent KOH. The effect of KOH concentration on cycle life was studied. The cycle regime was a stressful accelerated LEO, which consisted of a 27.5 min charge followed by a 17.5 min charge (2 x normal rate). The depth of discharge (DOD) was 80 percent. The cell temperature was maintained at 23 C. The next step is to validate these results using flight hardware and a real time LEO test. NASA Lewis has a contract with the Naval Weapons Support Center (NWSC), Crane, Indiana, to validate the boiler plate test results. Six 48 A-hr Hughes recirculation design IPV nickel-hydrogen flight battery cells are being evaluated. Three of the cells contain 26 percent KOH (test cells) and three contain 31 percent KOH (control cells). They are undergoing real time LEO cycle life testing. The cycle regime is a 90-min LEO orbit consisting of a 54-min charge followed by a 36-min discharge. The depth-of-discharge is 80 percent. The cell temperature is maintained at 10 C. The cells were cycled for over 8000 cycles in the continuing test. There were no failures for the cells containing 26 percent KOH. There was two failures, however, for the cells containing 31 percent KOH.

  10. The Space Motion of Leo I: The Mass of the Milky Way's Dark Matter Halo

    NASA Astrophysics Data System (ADS)

    Boylan-Kolchin, Michael; Bullock, James S.; Sohn, Sangmo Tony; Besla, Gurtina; van der Marel, Roeland P.

    2013-05-01

    We combine our Hubble Space Telescope measurement of the proper motion of the Leo I dwarf spheroidal galaxy (presented in a companion paper) with the highest resolution numerical simulations of Galaxy-size dark matter halos in existence to constrain the mass of the Milky Way's dark matter halo (M vir, MW). Despite Leo I's large Galactocentric space velocity (200 km s-1) and distance (261 kpc), we show that it is extremely unlikely to be unbound if Galactic satellites are associated with dark matter substructure, as 99.9% of subhalos in the simulations are bound to their host. The observed position and velocity of Leo I strongly disfavor a low-mass Milky Way: if we assume that Leo I is the least bound of the Milky Way's classical satellites, then we find that M vir, MW > 1012 M ⊙ at 95% confidence for a variety of Bayesian priors on M vir, MW. In lower mass halos, it is vanishingly rare to find subhalos at 261 kpc moving as fast as Leo I. Should an additional classical satellite be found to be less bound than Leo I, this lower limit on M vir, MW would increase by 30%. Imposing a mass-weighted ΛCDM prior, we find a median Milky Way virial mass of M vir, MW = 1.6 × 1012 M ⊙, with a 90% confidence interval of [1.0-2.4] × 1012 M ⊙. We also confirm a strong correlation between subhalo infall time and orbital energy in the simulations and show that proper motions can aid significantly in interpreting the infall times and orbital histories of satellites.

  11. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight battery cells

    NASA Technical Reports Server (NTRS)

    Smithrick, John J.; Hall, Stephen W.

    1990-01-01

    A breakthrough in the low-earth-orbit (LEO) cycle life of individual pressure vessel (IPV) nickel hydrogen battery cells is reported. The cycle life of boiler plate cells containing 26 percent potassium hydroxide (KOH) electrolyte was about 40,000 LEO cycles compared to 3500 cycles for cells containing 31 percent KOH. The effect of KOH concentration on cycle life was studied. The cycle regime was a stressful accelerated LEO, which consisted of a 27.5 min charge followed by a 17.5 min charge (2 x normal rate). The depth of discharge (DOD) was 80 percent. The cell temperature was maintained at 23 C. The next step is to validate these results using flight hardware and real time LEO test. NASA Lewis has a contract with the Naval Weapons Support Center (NWSC), Crane, Indiana to validate the boiler plate test results. Six 48 A-hr Hughes recirculation design IPV nickel-hydrogen flight battery cells are being evaluated. Three of the cells contain 26 percent KOH (test cells) and three contain 31 percent KOH (control cells). They are undergoing real time LEO cycle life testing. The cycle regime is a 90-min LEO orbit consisting of a 54-min charge followed by a 36-min discharge. The depth-of-discharge is 80 percent. The cell temperature is maintained at 10 C. The cells were cycled for over 8000 cycles in the continuing test. There were no failures for the cells containing 26 percent KOH. There were two failures, however, for the cells containing 31 percent KOH.

  12. A new concept for high-cycle-life LEO: Rechargeable MnO2-hydrogen

    NASA Technical Reports Server (NTRS)

    Appleby, A. J.; Dhar, H. P.; Kim, Y. J.; Murphy, O. J.

    1989-01-01

    The nickel-hydrogen secondary battery system, developed in the early 1970s, has become the system of choice for geostationary earth orbit (GEO) applications. However, for low earth orbit (LEO) satellites with long expected lifetimes the nickel positive limits performance. This requires derating of the cell to achieve very long cycle life. A new system, rechargeable MnO2-Hydrogen, which does not require derating, is described here. For LEO applications, it promises to have longer cycle life, high rate capability, a higher effective energy density, and much lower self-discharge behavior than those of the nickel-hydrogen system.

  13. Magnitude Standardization Procedure for OWL-Net Optical Observations of LEO Satellites

    NASA Astrophysics Data System (ADS)

    Roh, Dong-Goo; Choi, Jin; Jo, Jung Hyun; Yim, Hong-Suh; Park, Sun-Youp; Park, Maru; Choi, Young-Jun; Bae, Young-Ho; Park, Young-Sik; Jang, Hyun-Jung; Cho, Sungki; Kim, Ji-Hye; Park, Jang-Hyun

    2015-12-01

    As a governmentally approved domestic entity for Space Situational Awareness, Korea Astronomy and Space Science Institute (KASI) is developing and operating an optical telescopes system, Optical Wide-field PatroL (OWL) Network. During the test phase of this system, it is necessary to determine the range of brightness of the observable satellites. We have defined standard magnitude for Low Earth Orbit (LEO) satellites to calibrate their luminosity in terms of standard parameters such as distance, phase angle, and angular rate. In this work, we report the optical brightness range of five LEO Satellites using OWL-Net.

  14. Standard for Solar Array Arc-Prevention in LEO - NASA 4005

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.

    2006-01-01

    Spacecraft charging in Low Earth Orbit (LEO) is commonly caused by the high voltage (>55 V) solar array power system. Conversely, arcing on the solar arrays is an undesirable consequence of the spacecraft charging. The new NASA Low Earth Orbit Spacecraft Charging Design Standard and Information Handbook (NASA-4005) presents a standard and all the necessary background information to understand how to eliminate solar array arcing on LEO spacecraft in the design stage, before the spacecraft is built, and before costly retrofits are needed.

  15. DWARF IRREGULAR GALAXY LEO A: SUPRIME-CAM WIDE-FIELD STELLAR PHOTOMETRY

    SciTech Connect

    Stonkutė, Rima; Narbutis, Donatas; Vansevičius, Vladas; Arimoto, Nobuo; Hasegawa, Takashi; Tamura, Naoyuki

    2014-10-01

    We have surveyed a complete extent of Leo A—an apparently isolated gas-rich low-mass dwarf irregular galaxy in the Local Group. The B, V, and I passband CCD images (typical seeing ∼0.''8) were obtained with the Subaru Telescope equipped with the Suprime-Cam mosaic camera. The wide-field (20' × 24') photometry catalog of 38,856 objects (V ∼ 16-26 mag) is presented. This survey is also intended to serve as ''a finding chart'' for future imaging and spectroscopic observation programs of Leo A.

  16. Ever Ready to Go: The Multiple Exiles of Leo Szilard

    NASA Astrophysics Data System (ADS)

    Frank, Tibor

    2005-06-01

    I argue that to understand the life and work of Leo Szilard (1898 1964) we have to understand, first, that he was driven by events to numerous departures, escapes, and exiles, changing his religion, his language, his country of residence, and his scientific disciplines; second, that he was a man haunted by major moral dilemmas throughout his life, burdened by a sincere and grave sense of responsibility for the fate of the world; and third, that he experienced a terrible sense of déjà vu: his excessive sensitivity and constant alertness were products of his experiences as a young student in Budapest in 1919. The mature Szilard in Berlin of 1933, and forever after, was always ready to move. I proceed as follows:After a brief introduction to his family background, youth, and education in Budapest, I discuss the impact of his army service in the Great War and of the tumultous events in Hungary in 1918 1919 on his life and psyche, forcing him to leave Budapest for Berlin in late 1919. He completed his doctoral degree under Max von Laue (1879 1960) at the University of Berlin in 1922 and his Habilitationsschrift in 1925. During the 1920s and early 1930s, he filed a number of patents, several of them jointly with Albert Einstein (1879 1955). He left Berlin in March 1933 for London where he played a leading role in the rescue operations for refugee scientists and scholars from Nazi Germany. He also carried out notable research in nuclear physics in London and Oxford before immigrating to the United States at the end of 1938. He drafted Einstein’s famous letter of August 2, 1939, to President Franklin D. Roosevelt, worked in the Manhattan Project during World War II, initiated a petition to President Harry S. Truman not to use the bomb on Japan, and immediately after the war was a leader in the scientists’ movement that resulted in civilian control of nuclear energy. In 1946 he turned to biology, in which his most significant contribution was to formulate a theory of

  17. Volcanic Activity on lo at the Time of the Ulysses Encounter.

    PubMed

    Spencer, J R; Howell, R R; Clark, B E; Klassen, D R; O'connor, D

    1992-09-11

    The population of heavy ions in lo's torus is ultimately derived from lo volcanism. Groundbased infrared observations of lo between October 1991 and March 1992, contemporaneous with the 8 February 1992 Ulysses observations of the lo torus, show that volcanic thermal emission was at the low end of the normal range at all lo longitudes during this period. In particular, the dominant hot spot Loki was quiescent. Resolved images show that there were at least four hot spots on lo's Jupiter-facing hemisphere, including Loki and a long-lived spot on the leading hemisphere (Kanehekili), of comparable 3.5-micrometer brightness but higher temperature.

  18. END/MMOD: A Synergic Combination of a LEO Spacecraft Aero-Braking Deorbiting Module with a LEO Space Debris and Micro-Meteoroids Detection and Characterization System

    NASA Astrophysics Data System (ADS)

    Balduccini, Mauro; Raponi, Luca; Nascetti, Augusto; Bertini, Fabrizio; Gallucci, Stefano

    2013-08-01

    In this paper it is proposed the combination of the End-of-life Natural Deorbiting (END) module (an inflatable aerobreaking device already under development in AVIO and aimed to accelerate the orbital decay of inoperative spacecraft) with a sub-system called MMOD (Micro-Meteoroids and Orbital Debris) consisting of a hypervelocity impacts detector capable of collecting data relevant to the type and the distribution of space debris and micro-meteoroids in the LEO region.

  19. Leo de Ball and his contributions to international astronomical projects around 1900. (German Title: Leo de Ball und seine Beiträge zu internationalen Astronomieprojekten um 1900)

    NASA Astrophysics Data System (ADS)

    Habison, Peter

    From 1891 until 1916 Leo de Ball was the director of the Kuffner Observatory in Vienna. Born in Germany in 1853, he studied at Berlin and Bonn. After having received his doctorate in 1877, he became assistant at Gotha. From 1881 to 1882 he worked at the observatory in Bothkamp, where he discovered the minor planet ``Athamantis''. In 1883, he followed an invitation to the Ougrée Observatory in Belgium. Here he published some quite remarkable papers on the mass of Saturn and was also introduced to meridian circle astronomy. In 1891 he received a call to Moriz von Kuffner's observatory in Vienna. During that time the Astronomische Gesellschaft called for an extension of the ``Zonenunternehmen'' to southern declinations from -2 ° to -23°. De Ball took over the zone -5°50´ to -10°50´. This work occupied most of his time from 1892 to 1896. In 1900 Leo de Ball initiated a project for determining relative parallaxes of 252 stars in collaboration with four observatories. Although the project was only partly executed, Leo de Ball published relative parallaxes of 16 stars, observed from 1901 to 1907 with the Vienna heliometer.

  20. Volumetric HiLo microscopy employing an electrically tunable lens.

    PubMed

    Philipp, Katrin; Smolarski, André; Koukourakis, Nektarios; Fischer, Andreas; Stürmer, Moritz; Wallrabe, Ulrike; Czarske, Jürgen W

    2016-06-27

    Electrically tunable lenses exhibit strong potential for fast motion-free axial scanning in a variety of microscopes. However, they also lead to a degradation of the achievable resolution because of aberrations and misalignment between illumination and detection optics that are induced by the scan itself. Additionally, the typically nonlinear relation between actuation voltage and axial displacement leads to over- or under-sampled frame acquisition in most microscopic techniques because of their static depth-of-field. To overcome these limitations, we present an Adaptive-Lens-High-and-Low-frequency (AL-HiLo) microscope that enables volumetric measurements employing an electrically tunable lens. By using speckle-patterned illumination, we ensure stability against aberrations of the electrically tunable lens. Its depth-of-field can be adjusted a-posteriori and hence enables to create flexible scans, which compensates for irregular axial measurement positions. The adaptive HiLo microscope provides an axial scanning range of 1 mm with an axial resolution of about 4 μm and sub-micron lateral resolution over the full scanning range. Proof of concept measurements at home-built specimens as well as zebrafish embryos with reporter gene-driven fluorescence in the thyroid gland are shown. PMID:27410654

  1. First light curve and period study of LO Andromedae

    NASA Astrophysics Data System (ADS)

    Gürol, B.; Müyesseroğlu, Z.

    2005-01-01

    New BV light curves and times of minimum light for the short period W UMa system LO And were analyzed to derive the preliminary physical parameters of the system. The light curves were obtained at Ankara University Observatory during 5 nights in 2003. A new ephemeris is determined for the times of primary minimum. The analysis of the light curves is made using the Wilson-Devinney 2003 code. The present solution reveals that LO And has a photometric mass ratio q = 0.371 and is an A-type contact binary. The period of the system is still increasing, which can be attributed to light-time effect and mass transfer between the components. With the assumption of coplanar orbit of the third body the revealed mass is M3 = 0.21M. If the period change dP/dt = 0.0212 sec/yr is caused only by the mass transfer between components (from the lighter component to the heavier) the calculated mass transfer rate is dm/dt = 1.682 10-7M/yr. The absolute radii and masses estimated for the components, based on our photometric solution and the absolute parameters of the systems which have nearly same period are R1 = 1.30R, R2 = 0.85R, M1 = 1.31M, M2 = 0.49M respectively for the primary and secondary components.

  2. Human CD34(lo)CD133(lo) fetal liver cells support the expansion of human CD34(hi)CD133(hi) hematopoietic stem cells.

    PubMed

    Yong, Kylie Su Mei; Keng, Choong Tat; Tan, Shu Qi; Loh, Eva; Chang, Kenneth Te; Tan, Thiam Chye; Hong, Wanjin; Chen, Qingfeng

    2016-09-01

    We have recently discovered a unique CD34(lo)CD133(lo) cell population in the human fetal liver (FL) that gives rise to cells in the hepatic lineage. In this study, we further characterized the biological functions of FL CD34(lo)CD133(lo) cells. Our findings show that these CD34(lo)CD133(lo) cells express markers of both endodermal and mesodermal lineages and have the capability to differentiate into hepatocyte and mesenchymal lineage cells by ex vivo differentiation assays. Furthermore, we show that CD34(lo)CD133(lo) cells express growth factors that are important for human hematopoietic stem cell (HSC) expansion: stem cell factor (SCF), insulin-like growth factor 2 (IGF2), C-X-C motif chemokine 12 (CXCL12), and factors in the angiopoietin-like protein family. Co-culture of autologous FL HSCs and allogenic HSCs derived from cord blood with CD34(lo)CD133(lo) cells supports and expands both types of HSCs.These findings are not only essential for extending our understanding of the HSC niche during the development of embryonic and fetal hematopoiesis but will also potentially benefit adult stem cell transplantations in clinics because expanded HSCs demonstrate the same capacity as primary cells to reconstitute the human immune system and mediate long-term hematopoiesis in vivo. Together, CD34(lo)CD133(lo) cells not only serve as stem/progenitor cells for liver development but are also an essential component of the HSC niche in the human FL. PMID:27593483

  3. Human CD34(lo)CD133(lo) fetal liver cells support the expansion of human CD34(hi)CD133(hi) hematopoietic stem cells.

    PubMed

    Yong, Kylie Su Mei; Keng, Choong Tat; Tan, Shu Qi; Loh, Eva; Chang, Kenneth Te; Tan, Thiam Chye; Hong, Wanjin; Chen, Qingfeng

    2016-09-01

    We have recently discovered a unique CD34(lo)CD133(lo) cell population in the human fetal liver (FL) that gives rise to cells in the hepatic lineage. In this study, we further characterized the biological functions of FL CD34(lo)CD133(lo) cells. Our findings show that these CD34(lo)CD133(lo) cells express markers of both endodermal and mesodermal lineages and have the capability to differentiate into hepatocyte and mesenchymal lineage cells by ex vivo differentiation assays. Furthermore, we show that CD34(lo)CD133(lo) cells express growth factors that are important for human hematopoietic stem cell (HSC) expansion: stem cell factor (SCF), insulin-like growth factor 2 (IGF2), C-X-C motif chemokine 12 (CXCL12), and factors in the angiopoietin-like protein family. Co-culture of autologous FL HSCs and allogenic HSCs derived from cord blood with CD34(lo)CD133(lo) cells supports and expands both types of HSCs.These findings are not only essential for extending our understanding of the HSC niche during the development of embryonic and fetal hematopoiesis but will also potentially benefit adult stem cell transplantations in clinics because expanded HSCs demonstrate the same capacity as primary cells to reconstitute the human immune system and mediate long-term hematopoiesis in vivo. Together, CD34(lo)CD133(lo) cells not only serve as stem/progenitor cells for liver development but are also an essential component of the HSC niche in the human FL.

  4. Human CD34loCD133lo fetal liver cells support the expansion of human CD34hiCD133hi hematopoietic stem cells

    PubMed Central

    Yong, Kylie Su Mei; Keng, Choong Tat; Tan, Shu Qi; Loh, Eva; Chang, Kenneth TE; Tan, Thiam Chye; Hong, Wanjin; Chen, Qingfeng

    2016-01-01

    We have recently discovered a unique CD34loCD133lo cell population in the human fetal liver (FL) that gives rise to cells in the hepatic lineage. In this study, we further characterized the biological functions of FL CD34loCD133lo cells. Our findings show that these CD34loCD133lo cells express markers of both endodermal and mesodermal lineages and have the capability to differentiate into hepatocyte and mesenchymal lineage cells by ex vivo differentiation assays. Furthermore, we show that CD34loCD133lo cells express growth factors that are important for human hematopoietic stem cell (HSC) expansion: stem cell factor (SCF), insulin-like growth factor 2 (IGF2), C-X-C motif chemokine 12 (CXCL12), and factors in the angiopoietin-like protein family. Co-culture of autologous FL HSCs and allogenic HSCs derived from cord blood with CD34loCD133lo cells supports and expands both types of HSCs.These findings are not only essential for extending our understanding of the HSC niche during the development of embryonic and fetal hematopoiesis but will also potentially benefit adult stem cell transplantations in clinics because expanded HSCs demonstrate the same capacity as primary cells to reconstitute the human immune system and mediate long-term hematopoiesis in vivo. Together, CD34loCD133lo cells not only serve as stem/progenitor cells for liver development but are also an essential component of the HSC niche in the human FL. PMID:27593483

  5. Effects of Long-Term Irradiation with LEO Environment Effective Factors on Properties of Solid Lubricant

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koji; Tagawa, Masahito; Akiyama, Masao

    This study evaluated effects of a low earth orbit (LEO) space environment on properties of a solid lubricant used for space applications. The tested lubricant was a bonded MoS2 film with organic binder. The film was exposed to a real LEO space environment aboard the International Space Station (ISS) by the Space Environment Exposure Device (SEED) experiment for about 1400 days. Additionally, it was irradiated individually with atomic oxygen (AO), ultraviolet rays (UV), and electron beam (EB) on the ground. Fluences of these factors corresponded to exposure to the LEO environment by the SEED experiment. Friction tests in vacuum and surface analyses were carried out for the samples. Tribological behavior of the different samples was measured using classical reciprocating pin-on-flat friction tests. Furthermore, XPS analysis was performed for the film surface and rubbing tracks of the samples. Results show that the friction coefficient decreased by AO irradiation at an early stage of the tests. It resembled the result of the film exposed to the real LEO environment.

  6. THE LEO IV DWARF SPHEROIDAL GALAXY: COLOR-MAGNITUDE DIAGRAM AND PULSATING STARS

    SciTech Connect

    Moretti, Maria Ida; Dall'Ora, Massimo; Ripepi, Vincenzo E-mail: dallora@na.astro.it

    2009-07-10

    We present the first V, B - V color-magnitude diagram of the Leo IV dwarf spheroidal galaxy, a faint Milky Way satellite recently discovered by the Sloan Digital Sky Survey. We have obtained B, V time-series photometry reaching about half a magnitude below the Leo IV turnoff, which we detect at V = 24.7 mag, and have performed the first study of the variable star population. We have identified three RR Lyrae stars (all fundamental-mode pulsators, RRab) and one SX Phoenicis variable in the galaxy. In the period-amplitude diagram the Leo IV RR Lyrae stars are located close to the loci of Oosterhoff type I systems and the evolved fundamental-mode RR Lyrae stars in the Galactic globular cluster M3. However, their mean pulsation period, (Pab) = 0.655 days, would suggest an Oosterhoff type II classification for this galaxy. The RR Lyrae stars trace very well the galaxy's horizontal branch, setting its average magnitude at (V {sub RR}) = 21.48 {+-} 0.03 mag (standard deviation of the mean). This leads to a distance modulus of {mu}{sub 0} = 20.94 {+-} 0.07 mag, corresponding to a distance of 154 {+-} 5 kpc, by adopting for the Leo IV dSph a reddening E(B - V) = 0.04 {+-} 0.01 mag and a metallicity of [Fe/H] = -2.31 {+-} 0.10.

  7. Sizing of "Mother Ship and Catcher" Concepts for LEO Small Debris Capture

    NASA Technical Reports Server (NTRS)

    Bacon, John B.

    2009-01-01

    Most Low Earth Orbit (LEO) debris lies in a limited number of inclination "bands" associated with launch latitudes, or with specific useful orbit inclinations (such as polar orbits). Such narrow inclination bands generally have a uniform spread over all possible Right Ascensions of Ascending Node (RAANs), creating a different orbit plane for nearly every piece of debris. This complicates concept of rendezvous and capture for debris removal. However, a low-orbiting satellite will always phase in RAAN faster than debris objects in higher orbits at the same inclination, potentially solving the problem. Such a base can serve as a single space-based launch facility (a "mother ship") that can tend and then send tiny individual catcher devices for each debris object, as the facility drifts into the same RAAN as the higher object. This presentation will highlight characteristic system requirements of such an architecture, including structural and navigation requirements, power, mass and dV budgets for both the mother ship and the mass-produced common catcher devices that would clean out selected inclination bands. The altitude and inclination regime over which a band is to be cleared, the size distribution of the debris, and the inclusion of additional mission priorities all affect the sizing of the system. It is demonstrated that major LEO hazardous debris reductions can be realized in each band with a single LEO launch of a single mother ship, with simple attached catchers of total mass less than typical commercial LEO launch capability.

  8. Leo Kanner's Mention of 1938 in His Report on Autism Refers to His First Patient

    ERIC Educational Resources Information Center

    Olmsted, Dan; Blaxill, Mark

    2016-01-01

    Leo Kanner begins his landmark 1943 case series on autistic children by stating the condition was first brought to his attention in 1938. Recent letters to "JADD" have described this reference as "mysterious" and speculated it refers to papers published that year by Despert or Asperger. In fact, as Kanner goes on to state, 1938…

  9. An efficient QoS-aware routing algorithm for LEO polar constellations

    NASA Astrophysics Data System (ADS)

    Tian, Xin; Pham, Khanh; Blasch, Erik; Tian, Zhi; Shen, Dan; Chen, Genshe

    2013-05-01

    In this work, a Quality of Service (QoS)-aware routing (QAR) algorithm is developed for Low-Earth Orbit (LEO) polar constellations. LEO polar orbits are the only type of satellite constellations where inter-plane inter-satellite links (ISLs) are implemented in real world. The QAR algorithm exploits features of the topology of the LEO satellite constellation, which makes it more efficient than general shortest path routing algorithms such as Dijkstra's or extended Bellman-Ford algorithms. Traffic density, priority, and error QoS requirements on communication delays can be easily incorporated into the QAR algorithm through satellite distances. The QAR algorithm also supports efficient load balancing in the satellite network by utilizing the multiple paths from the source satellite to the destination satellite, and effectively lowers the rate of network congestion. The QAR algorithm supports a novel robust routing scheme in LEO polar constellation, which is able to significantly reduce the impact of inter-satellite link (ISL) congestions on QoS in terms of communication delay and jitter.

  10. Raising a Child in the Punana Leo: Everyone (Men and Women) Play an Important Role

    ERIC Educational Resources Information Center

    Iokepa-Guerrero, Noelani

    2008-01-01

    Established in 1983 by a group of parents and teachers, the 'Aha Punana Leo ('APL) was formed. A grassroots organization, 'APL was established to respond to the dismal plight of the Hawaiian language. Just a mere 25 years ago, the Hawaiian language was on the verge of being lost forever. Through the dedicated efforts of a small group of friends…

  11. Leo Strauss and the Neoconservative Critique of the Liberal University: Postmodernism, Relativism and the Culture Wars

    ERIC Educational Resources Information Center

    Peters, Michael A.

    2008-01-01

    This paper examines the neoconservative critique of the university and particularly the attack on multiculturalism and postmodernism that initiated the culture wars. It seeks to explain these developments by an analysis of the thought of Leo Strauss. The paper begins by providing an introduction to US neoconservatism and latest challenges to it…

  12. ENR selects Leo P. Duffy as its 1993 man of the year

    SciTech Connect

    Rubin, D.K.

    1993-02-15

    This article is a discussion of the appointment of Leo Duffy as the leader of the US DOE`s cleanup of its several nuclear weapons facilities. A professional sketch of Mr. Duffy is provided, and the problems that he will encounter are also outlined.

  13. VARIABILITY AND STAR FORMATION IN LEO T, THE LOWEST LUMINOSITY STAR-FORMING GALAXY KNOWN TODAY

    SciTech Connect

    Clementini, Gisella; Cignoni, Michele; Ramos, Rodrigo Contreras; Federici, Luciana; Tosi, Monica; Ripepi, Vincenzo; Marconi, Marcella; Musella, Ilaria E-mail: rodrigo.contreras@oabo.inaf.it E-mail: monica.tosi@oabo.inaf.it E-mail: ripepi@na.astro.it E-mail: ilaria@na.astro.it

    2012-09-10

    We present results from the first combined study of variable stars and star formation history (SFH) of the Milky Way 'ultra-faint' dwarf (UFD) galaxy Leo T, based on F606W and F814W multi-epoch archive observations obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. We have detected 14 variable stars in the galaxy. They include one fundamental-mode RR Lyrae star and 11 Anomalous Cepheids with periods shorter than 1 day, thus suggesting the occurrence of multiple star formation episodes in this UFD, of which one about 10 Gyr ago produced the RR Lyrae star. A new estimate of the distance to Leo T of 409{sup +29}{sub -27} kpc (distance modulus of 23.06 {+-} 0.15 mag) was derived from the galaxy's RR Lyrae star. Our V, V - I color-magnitude diagram (CMD) of Leo T reaches V {approx} 29 mag and shows features typical of a galaxy in transition between dwarf irregular and dwarf spheroidal types. A quantitative analysis of the SFH, based on the comparison of the observed V, V - I CMD with the expected distribution of stars for different evolutionary scenarios, confirms that Leo T has a complex SFH dominated by two enhanced periods about 1.5 and 9 Gyr ago, respectively. The distribution of stars and gas shows that the galaxy has a fairly asymmetric structure.

  14. Establishing a Robotic, LEO-to-GEO Satellite Servicing Infrastructure as an Economic Foundation for Exploration

    NASA Technical Reports Server (NTRS)

    Horsham, Gary A. P.; Schmidt, George R.; Gilland, James H.

    2010-01-01

    The strategy for accomplishing civilian exploration goals and objectives is in the process of a fundamental shift towards a potential new approach called Flexible Path. This paper suggests that a government-industry or public-private partnership in the commercial development of low Earth orbit to geostationary orbit (LEO-to-GEO (LTG)) space, following or in parallel with the commercialization of Earth-to-LEO and International Space Station (ISS) operations, could serve as a necessary, logical step that can be incorporated into the flexible path approach. A LTG satellite-servicing infrastructure and architecture concept is discussed within this new strategic context. The concept consists of a space harbor that serves as a transport facility for a fleet of specialized, fully- or semi-autonomous robotic servicing spacecraft. The baseline, conceptual system architecture is composed of a space harbor equipped with specialized servicer spacecraft; a satellite command, communication, and control system; a parts station; a fuel station or depot; and a fuel/parts replenishment transport. The commercial servicer fleet would consist of several types of spacecraft, each designed with specialized robotic manipulation subsystems to provide services such as refueling, upgrade, repair, inspection, relocation, and removal. The space harbor is conceptualized as an ISS-type, octagonal truss structure equipped with radiation tolerant subsystems. This space harbor would be primarily capable of serving as an operational platform for various commercially owned and operated servicer spacecraft positioned and docked symmetrically on four of the eight sides. Several aspects of this concept are discussed, such as: system-level feasibility in terms of ISS-truss-type infrastructure and subsystems emplacement and maintenance between LEO and GEO; infrastructure components assembly in LEO, derived from ISS assembly experience, and transfer to various higher orbital locations; the evolving Earth

  15. Leo de Ball and his Contribution to International Astrometry Projects around 1900

    NASA Astrophysics Data System (ADS)

    Habison, P.

    Leo de Ball was born in Lobberich at the German-Dutch border in 1853. From 1871 onwards he studied astronomy and physics at the universities in Berlin and Bonn. After having received his doctorate in 1877 he became assistant at the ``Herzogliche Sternwarte in Gotha''. From 1881-82 he spent two years at the ``Sternwarte des Kammerherrn von Bülow'' in Bothkamp. There he discovered the minor planet ``Athamantis'' on 3 September 1882. In 1883 he followed an invitation from Folie to the observatory Ougrée near Lüttich. There he published four remarkable papers on stellar and planetary astrometry. In 1891 he received a call to Moriz von Kuffners observatory in Vienna and was assigned director of this young institute. In the same year he started to participate in international projects. During that time it was suggested to extend the ``Zonenunternehmen der Astronomischen Gesellschaft'' also to southern declinations. Leo de Ball contributed to this project and Kuffner Observatory was assigned the southern declination zone from -6 to -10 degrees. This work occupied most of his time from 1892 to 1902. The catalogue of 8468 stars down to magnitude nine was finally published in 1904. In 1900 Leo de Ball initiated a new project for determining relative parallaxes of 252 stars in collaboration with four observatories in Europe and the United States. Although the project was only partly realized, Leo de Ball published relative parallaxes of 16 stars, observed from 1901-07 with the Vienna heliometer. The talk will give a brief overview of Leo de Ball's life and will then focus on his work and international collaborations from 1891-1916.

  16. LEO P: HOW MANY METALS CAN A VERY LOW MASS, ISOLATED GALAXY RETAIN?

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dolphin, Andrew; Cannon, John M.; Salzer, John J.; Rhode, Katherine L.; Adams, Elizabeth A. K.; Berg, Danielle; Giovanelli, Riccardo; Haynes, Martha P.

    2015-12-20

    Leo P is a gas-rich dwarf galaxy with an extremely low gas-phase oxygen abundance (3% solar). The isolated nature of Leo P enables a quantitative measurement of metals lost solely due to star formation feedback. We present an inventory of the oxygen atoms in Leo P based on the gas-phase oxygen abundance measurement, the star formation history (SFH), and the chemical enrichment evolution derived from resolved stellar populations. The SFH also provides the total amount of oxygen produced. Overall, Leo P has retained 5% of its oxygen; 25% of the retained oxygen is in the stars while 75% is in the gas phase. This is considerably lower than the 20%–25% calculated for massive galaxies, supporting the trend for less efficient metal retention for lower-mass galaxies. The retention fraction is higher than that calculated for other alpha elements (Mg, Si, Ca) in dSph Milky Way satellites of similar stellar mass and metallicity. Accounting only for the oxygen retained in stars, our results are consistent with those derived for the alpha elements in dSph galaxies. Thus, under the assumption that the dSph galaxies lost the bulk of their gas mass through an environmental process such as tidal stripping, the estimates of retained metal fractions represent underestimates by roughly a factor of four. Because of its isolation, Leo P provides an important datum for the fraction of metals lost as a function of galaxy mass due to star formation.

  17. Alfalfa discovery of the nearby gas-rich dwarf galaxy Leo P. IV. Distance measurement from LBT optical imaging

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Berg, Danielle; Cannon, John M.; Salzer, John J.; Rhode, Katherine L.; Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P.; Dolphin, Andrew E-mail: skillman@astro.umn.edu E-mail: jcannon@macalester.edu E-mail: slaz@astro.indiana.edu E-mail: riccardo@astro.cornell.edu

    2013-12-01

    Leo P is a low-luminosity dwarf galaxy discovered through the blind H I Arecibo Legacy Fast ALFA survey. The H I and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with both active star formation and an underlying older population, as well as an extremely low oxygen abundance. Here, we measure the distance to Leo P by applying the tip of the red giant branch (TRGB) distance method to photometry of the resolved stellar population from new Large Binocular Telescope V and I band imaging. We measure a distance modulus of 26.19{sub −0.50}{sup +0.17} mag corresponding to a distance of 1.72{sub −0.40}{sup +0.14} Mpc. Although our photometry reaches 3 mag below the TRGB, the sparseness of the red giant branch yields higher uncertainties on the lower limit of the distance. Leo P is outside the Local Group with a distance and velocity consistent with the local Hubble flow. While located in a very low-density environment, Leo P lies within ∼0.5 Mpc of a loose association of dwarf galaxies which include NGC 3109, Antlia, Sextans A, and Sextans B, and 1.1 Mpc away from its next nearest neighbor, Leo A. Leo P is one of the lowest metallicity star-forming galaxies known in the nearby universe, comparable in metallicity to I Zw 18 and DDO 68, but with stellar characteristics similar to dwarf spheriodals (dSphs) in the Local Volume such as Carina, Sextans, and Leo II. Given its physical properties and isolation, Leo P may provide an evolutionary link between gas-rich dwarf irregular galaxies and dSphs that have fallen into a Local Group environment and been stripped of their gas.

  18. Risk assessment of Cumberland unit 2 L-O blades

    SciTech Connect

    Lam, T.C.T.; Puri, A.

    1996-12-31

    Concern about the reliability of the 1,300 mw Cumberland steam turbine units after an unexpected blade tip failure in the fall of 1995 caused TVA to conduct an investigation into the current reliability of the L-O blades. A probabilistic model based on the measured frequencies, damping and material fatigue data was generated. The influence of significant erosion damage on the blade natural frequencies and on the local stresses was estimated. A probabilistic model of the local fatigue limit was generated based on test data. Monte Carlo simulation was employed to estimate the probability of blade failure by comparing the dynamic stress with the fatigue limit. Risk assessment of the blade failure is presented.

  19. Responsivity calibration of the LoWEUS spectrometer

    NASA Astrophysics Data System (ADS)

    Lepson, J. K.; Beiersdorfer, P.; Kaita, R.; Majeski, R.; Boyle, D.

    2016-11-01

    We performed an in situ calibration of the relative responsivity function of the Long-Wavelength Extreme Ultraviolet Spectrometer (LoWEUS), while operating on the Lithium Tokamak Experiment (LTX) at Princeton Plasma Physics Laboratory. The calibration was accomplished by measuring oxygen lines, which are typically present in LTX plasmas. The measured spectral line intensities of each oxygen charge state were then compared to the calculated emission strengths given in the CHIANTI atomic database. Normalizing the strongest line in each charge state to the CHIANTI predictions, we obtained the differences between the measured and predicted values for the relative strengths of the other lines of a given charge state. We find that a 3rd degree polynomial function provides a good fit to the data points. Our measurements show that the responsivity between about 120 and 300 Å varies by factor of ˜30.

  20. Magnetic retention of LO2 in an accelerating environment

    NASA Astrophysics Data System (ADS)

    Marchetta, Jeffrey G.; Simmons, Benjamin D.; Hochstein, John I.

    2008-04-01

    Recent advances in magnet technology suggest that magnetic positive positioning of liquids may become a viable technology for future spacecraft systems. Preliminary simulation results for a subscale tank are presented which illustrate that a magnet of sufficient strength can retain liquid oxygen (LO2) in an accelerating environment. Development of a new computational model for simulating equilibrium free surface shapes in the presence of a magnetic field is presented. Comparisons of equilibrium simulation predictions to known solutions for simple configurations support the conclusion that the computational model is suitable for continuing the investigation of magnetic propellant storage. Results obtained using the equilibrium simulation are presented to further demonstrate the feasibility of using magnetic retention to manage cryogenic propellants onboard spacecraft.

  1. MaTeLo: Automated Testing Suite for Software Validation

    NASA Astrophysics Data System (ADS)

    Guiotto, A.; Acquaroli, B.; Martelli, A.

    It is universally known that testing has a predominant role when developing software: more and more efforts are spent on testing to detect programming faults, to evaluate the code reliability or performance, to ensure that a critical function of a system meets given requirements. The ratio of time spent on testing should not be neglected and this explains why there is a real need to improve the development process, especially as systems are becoming larger and larger. It is necessary to keep under control the schedule and budget of developments, and controlling the testing phase is a real issue, often underestimated in many industrial sectors. The industry is heightened at different stages regarding testing, and the MaTeLo project is committed to promote the use of statistical tools &methods to answer European industry's needs: • have the ability to choose relevant test cases instead of a human- biased selection • know when to stop testing (definition of a stopping criteria) instead of a vague and informal criteria • adopt an identical strategy for different developments • automate the testing process, and thus to make testing not human error prone MaTeLo (Markov Test Logic) study is a study currently under development in the frame of the IST program of the European Community. The aim of the project is to define, implement and validate a new approach for supporting the software testing activities in various industrial fields. One of the major goals is in particular to provide the software teams with a new tool able to automatically produce and execute the Test Cases starting from the software specifications. Further, the tool is conceived to provide metrics that could help technical staff to determine software quality and to evaluate how much expected results are met. The tool is based on Markov chains theory and belongs to statistical testing software tools family [Runeson] [Whittaker].

  2. A FIRST MEASUREMENT OF THE PROPER MOTION OF THE LEO II DWARF SPHEROIDAL GALAXY

    SciTech Connect

    Lepine, Sebastien; Koch, Andreas; Rich, R. Michael; Kuijken, Konrad

    2011-11-10

    We use 14 year baseline images obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST) to derive a proper motion for one of the Milky Way's most distant dwarf spheroidal companions, Leo II, relative to an extragalactic background reference frame. Astrometric measurements are performed in the effective point-spread function formalism using our own developed code. An astrometric reference grid is defined using 3224 stars that are members of Leo II and brighter than a magnitude of 25 in the F814W band. We identify 17 compact extragalactic sources, for which we measure a systemic proper motion relative to this stellar reference grid. We derive a proper motion [{mu}{sub {alpha},{mu}{delta}}] = [+104 {+-}113,-33 {+-} 151] {mu}as yr{sup -1} for Leo II in the heliocentric reference frame. Though marginally detected, the proper motion yields constraints on the orbit of Leo II. Given a distance of d {approx_equal} 230 kpc and a heliocentric radial velocity v{sub r} = +79 km s{sup -1}, and after subtraction of the solar motion, our measurement indicates a total orbital motion v{sub G} = 266.1 {+-} 128.7 km s{sup -1} in the Galactocentric reference frame, with a radial component v{sub r{sub G}}=21.5{+-}4.3 km s{sup -1} and tangential component v{sub t{sub G}} = 265.2 {+-} 129.4 km s{sup -1}. The small radial component indicates that Leo II either has a low-eccentricity orbit or is currently close to perigalacticon or apogalacticon distance. We see evidence for systematic errors in the astrometry of the extragalactic sources which, while close to being point sources, are slightly resolved in the HST images. We argue that more extensive observations at later epochs will be necessary to better constrain the proper motion of Leo II. We provide a detailed catalog of the stellar and extragalactic sources identified in the HST data which should provide a solid early-epoch reference for future astrometric measurements.

  3. Overview of battery usage in NASA/GSFC LEO and GEO missions

    NASA Technical Reports Server (NTRS)

    Yi, Thomas

    1989-01-01

    In July, 1989, Cosmic Background Explorer (COBE) will be launched from a Delta rocket to study the big bang theory. The COBE, which is in a LEO/Polar orbit, will have two 20 Ah NiCd batteries, and 18 cells per battery, made by McDonnell Douglas Company. In December, 1989, National Oceanic and Atmospheric Administration (NOAA-D) will be launched from an Atlas rocket for weather observation purposes. NOAA-D, which is in a LEO/Polar morning orbit, will have two 26.5 Ah NiCd batteries, and 17 cells per battery, made by Ge-Astro East Windor. NOAA-I, which is scheduled for May, 1991 launch in a LEO/Polar afternoon orbit, will have three 26.5 Ah NiCd batteries, 17 cells per battery, made by GE-Astro East Windor. In April, 1990, Gamma Ray Observatory (GRO) will be launched from STS37 to study the gamma ray radiation phenomenon. GRO, which is in a LEO orbit, will have two modular power systems (MPS) made by McDonnell Douglas, each MPS consisting of three 50 Ah NiCd batteries, 22 cells per battery. In July, 1990, Geostationary Operational Environmental Satellite (GOES-I) will be launched from an Atlas I rocket for weather observation purposes. GOES-I, which is in a GEO orbit, will have two 12 Ah NiCd batteries, 28 cells per battery, made by Ford Aerospace and Communications Company. In December, 1990, Tracking and Data Relay Satellite (TDRS-E) will be launched from STS43 for communication purposes. TDRS-E, which is in a GEO orbit, will have three 40 Ah NiCd batteries, 24 cells per battery, made by TRW. In August, 1991, Extreme Ultraviolet Explorer (EUVE) will be launched from a Delta rocket. EUVE, which is in a LEO orbit, will have one modular power system (MPS) made by McDonnell Douglas. In December, 1991, Upper Atmosphere Research Satellite (UARS) will be launched from STS50 to study the Earth's ozone layer and other environmental concerns. UARS, which is in a 56 deg inclination LEO orbit, will have one modular power systems (MPS) made by McDonnell Douglas.

  4. Phase center modeling for LEO GPS receiver antennas and its impact on precise orbit determination

    NASA Astrophysics Data System (ADS)

    Jäggi, Adrian; Dach, R.; Montenbruck, O.; Hugentobler, U.; Bock, H.; Beutler, G.

    2009-12-01

    Most satellites in a low-Earth orbit (LEO) with demanding requirements on precise orbit determination (POD) are equipped with on-board receivers to collect the observations from Global Navigation Satellite systems (GNSS), such as the Global Positioning System (GPS). Limiting factors for LEO POD are nowadays mainly encountered with the modeling of the carrier phase observations, where a precise knowledge of the phase center location of the GNSS antennas is a prerequisite for high-precision orbit analyses. Since 5 November 2006 (GPS week 1400), absolute instead of relative values for the phase center location of GNSS receiver and transmitter antennas are adopted in the processing standards of the International GNSS Service (IGS). The absolute phase center modeling is based on robot calibrations for a number of terrestrial receiver antennas, whereas compatible antenna models were subsequently derived for the remaining terrestrial receiver antennas by conversion (from relative corrections), and for the GNSS transmitter antennas by estimation. However, consistent receiver antenna models for space missions such as GRACE and TerraSAR-X, which are equipped with non-geodetic receiver antennas, are only available since a short time from robot calibrations. We use GPS data of the aforementioned LEOs of the year 2007 together with the absolute antenna modeling to assess the presently achieved accuracy from state-of-the-art reduced-dynamic LEO POD strategies for absolute and relative navigation. Near-field multipath and cross-talk with active GPS occultation antennas turn out to be important and significant sources for systematic carrier phase measurement errors that are encountered in the actual spacecraft environments. We assess different methodologies for the in-flight determination of empirical phase pattern corrections for LEO receiver antennas and discuss their impact on POD. By means of independent K-band measurements, we show that zero-difference GRACE orbits can be

  5. The chemical abundances of the stellar populations in the Leo I and II dSph galaxies

    NASA Astrophysics Data System (ADS)

    Bosler, Tammy L.; Smecker-Hane, Tammy A.; Stetson, Peter B.

    2007-06-01

    We have obtained calcium abundances and radial velocities for 102 red giant branch (RGB) stars in the Leo I dwarf spheroidal galaxy (dSph) and 74 RGB stars in the Leo II dSph using the low-resolution spectrograph (LRIS) on the Keck I 10-m telescope. We report on the calcium abundances [Ca/H] derived from the strengths of the CaII triplet absorption lines at 8498, 8542 and 8662 Å in the stellar spectra using a new empirical CaII triplet calibration to [Ca/H]. The two galaxies have different average [Ca/H] values of -1.34 +/- 0.02 for Leo I and -1.65 +/- 0.02 for Leo II with intrinsic abundance dispersions of 1.2 and 1.0 dex, respectively. The typical random and total errors in derived abundances are 0.10 and 0.17 dex per star. For comparison to the existing literature, we also converted our CaII measurements to [Fe/H] on the scale of Carretta and Gratton (1997) though we discuss why this may not be the best determinant of metallicity; Leo I has a mean [Fe/H] = -1.34 and Leo II has a mean [Fe/H] = -1.59. The metallicity distribution function of Leo I is approximately Gaussian in shape with an excess at the metal-rich end, while that of Leo II shows an abrupt cut-off at the metal-rich end. The lower mean metallicity of Leo II is consistent with the fact that it has a lower luminosity, hence lower the total mass than Leo I; thus, the evolution of Leo II may have been affected more by mass lost in galactic winds. Our direct and independent measurement of the metallicity distributions in these dSph will allow a more accurate star-formation histories to be derived from future analysis of their colour-magnitude diagrams(CMDs). Data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. E

  6. Extending the GPS satellite antenna patterns of the IGS to nadir angles beyond 14° using LEO data

    NASA Astrophysics Data System (ADS)

    Dach, R.; Jaeggi, A.; Bock, H.; Beutler, G.; Montenbruck, O.; Schmid, R.

    2010-12-01

    The absolute phase center model adopted by the International GNSS Service (IGS) in 2006 is based on robot calibrations for a number of terrestrial GNSS receiver antennas and consistent correction values for the GNSS transmitter antennas estimated from data of the global IGS tracking network. As the calibration of the satellite antennas is solely based on terrestrial measurements, the estimation of their phase patterns is limited to a nadir angle of 14°. This is not sufficient for the analysis of spaceborne GPS data collected by low Earth orbiting (LEO) satellites that record observations at nadir angles of up to 17°. Moreover, phase center variation (PCV) estimates for nadir angles close to 14° derived from terrestrial measurements might be affected by uncertainties in the troposphere modeling. This drawback could also be overcome by the use of LEO data. We use GPS tracking data from several LEO missions to extend the IGS satellite antenna patterns to nadir angles beyond 14°. In order to achieve estimates that are consistent with the PCVs currently used within the IGS, GPS and LEO orbits are fixed to solutions obtained by adopting the IGS conventional values. Due to significant near-field multipath effects in the LEO spacecraft environment, it is necessary to solve for GPS (nadir-dependent only) and LEO (azimuth- and elevation-dependent) antenna patterns simultaneously. We analyze the separability of these parameters and discuss appropriate constraints. We assess the contribution of different LEO missions to a combined solution and analyze the impact of LEO orbit modeling errors.

  7. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight cell - Update II

    NASA Astrophysics Data System (ADS)

    Smithrick, John J.; Hall, Stephen W.

    1992-04-01

    An update of validation test results confirming the breakthrough in LEO cycle life of nickel-hydrogen cells containing 26 percent KOH electrolyte is presented. A breakthrough in the LEO cycle life of individual pressure vessel (IPV) nickel-hydrogen cells has been previously reported. The cycle life of boiler plate cells containing 26 percent potassium hydroxide (KOH) electrolyte was about 40,000 LEO cycles, compared to 3500 cycles for cells containing 31 percent KOH. The cycle regime was a stressful accelerated LEO, which consisted of a 27.5 min charge followed by a 17.5 min discharge (2X normal rate). The depth-of-discharge was 80 percent. Six 48-Ah Hughes recirculation design IPV nickel-hydrogen flight battery cells are being evaluated. Three of the cells contain 26 percent KOH (test cells), and three contain 31 percent KOH (control cells). They are undergoing real time LEO cycle life testing. The cycle regime is a 90-min LEO orbit consisting of a 54-min charge followed by a 36-min discharge. The depth-of-discharge is 80 percent. The cell temperature is maintained at 10 C. The three 31 percent KOH cells failed (cycles 3729, 4165, and 11355). One of the 26 percent KOH cells failed at cycle 15314. The other two 26 percent KOH cells were cycled for over 16,000 cycles during the continuing test.

  8. LENTICULAR GALAXIES AT THE OUTSKIRTS OF THE LEO II GROUP: NGC 3599 AND NGC 3626

    SciTech Connect

    Sil'chenko, O. K.; Shulga, A. P.; Moiseev, A. V. E-mail: alina.shulga@gmail.co

    2010-11-15

    We have studied unbarred S0 galaxies, NGC 3599 and NGC 3626, the members of the X-ray bright group Leo II, by means of three-dimensional spectroscopy, long-slit spectroscopy, and imaging, with the aim of identifying the epoch and mechanisms of their transformation from spirals. Both galaxies have appeared to bear complex features obviously resulting from minor merging: decoupled gas kinematics, nuclear star-forming rings, and multi-tiered oval large-scale stellar disks. The weak emission line nucleus of NGC 3599 bears all signs of Seyfert activity, according to the line-ratio diagnostics of the gas excitation mechanism. We conclude that the transformation of these lenticular galaxies took place about 1-2 Gyr ago, through gravitational mechanisms unrelated to the hot intragroup medium of Leo II.

  9. Optimal GEO lasercomm terminal field of view for LEO link support

    NASA Astrophysics Data System (ADS)

    Hindman, Charles W.; Hunt, Jeffrey P.; Engberg, Brian S.; Walchko, Kevin J.

    2006-02-01

    As alternatives to the traditional gimbaled terminal design, future satellite based laser communications terminals are envisioned that utilize a wide field of view or field of regard (WFOV/WFOR). This approach can be advantageous in situations requiring rapid switching between user terminals, support for multiple terminals simultaneously (via TDMA, SDMA or WDMA) or other non-standard mission requirements. However, a traditional gimbaled terminal has the capability to continuously track a single user over very large angles, such as the 18-20° spanned by a LEO satellite as seen from GEO. WFOV/WFOR designs face increasing cost and/or complexity issues with each incremental increase in angular coverage. The methodology and inputs for a trade study are presented here that attempts to maximize the available connectivity to a LEO satellite while minimizing cost and complexity metrics by choosing an optimal FOV/FOR size for a GEO terminal.

  10. Time Serial Analysis of the Induced LEO Environment within the ISS 6A

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Nealy, John E.; Tomov, B. T.; Cucinotta, Francis A.; Badavi, Frank F.; DeAngelis, Giovanni; Atwell, William; Leutke, N.

    2006-01-01

    Anisotropies in the low Earth orbit (LEO) radiation environment were found to influence the thermoluminescence detectors (TLD) dose within the (International Space Station) ISS 7A Service Module. Subsequently, anisotropic environmental models with improved dynamic time extrapolation have been developed including westward and northern drifts using AP8 Min & Max as estimates of the historic spatial distribution of trapped protons in the 1965 and 1970 era, respectively. In addition, a directional dependent geomagnetic cutoff model was derived for geomagnetic field configurations from the 1945 to 2020 time frame. A dynamic neutron albedo model based on our atmospheric radiation studies has likewise been required to explain LEO neutron measurements. The simultaneous measurements of dose and dose rate using four Liulin instruments at various locations in the US LAB and Node 1 has experimentally demonstrated anisotropic effects in ISS 6A and are used herein to evaluate the adequacy of these revised environmental models.

  11. Microvariability of line profiles in the spectra of OB stars: III. The supergiant ρ LEO

    NASA Astrophysics Data System (ADS)

    Kholtygin, A. F.; Fabrika, S. N.; Burlakova, T. E.; Valyavin, G. G.; Chuntonov, G. A.; Kudryavtsev, D. O.; Kang, D.; Yushkin, M. V.; Galazutdinov, G. A.

    2007-11-01

    We observed the bright supergiant ρ Leo (B1 lab) in January-February 2004 using the 6-m telescope of the Special Astrophysical Observatory (Russia) and the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory (South Korea). 47 spectra with high time resolution (4-10 min), signal-to-noise ratios 300-1000, and spectral resolutions 45 000-60 000 were obtained. We detected variability in the HeI, SiII, SiIII, and NII line profiles, which may be due to rotational modulation of the profiles and photospheric pulsations of ρ Leo. The possible influence of the stellar magnetic field on the line-profile variations is discussed.

  12. Super NiCd Open-Circuit Storage and Low Earth Orbit (LEO) Life Test Evaluation

    NASA Technical Reports Server (NTRS)

    Baer, Jean Marie; Hwang, Warren C.; Ang, Valerie J.; Hayden, Jeff; Rao, Gopalakrishna; Day, John H. (Technical Monitor)

    2002-01-01

    This presentation discusses Air Force tests performed on super NiCd cells to measure their performance under conditions simulating Low Earth Orbit (LEO) conditions. Super NiCd cells offer potential advantages over existing NiCd cell designs including advanced cell design with improved separator material and electrode making processes, but handling and storage requires active charging. These tests conclude that the super NiCd cells support generic Air Force qualifications for conventional LEO missions (up to five years duration) and that handling and storage may not actually require active charging as previously assumed. Topics covered include: Test Plan, Initial Characterization Tests, Open-Circuit Storage Tests, and post storage capacities.

  13. Positive immunolabelling for feline infectious peritonitis in an African lion (Panthera leo) with bilateral panuveitis.

    PubMed

    Mwase, M; Shimada, K; Mumba, C; Yabe, J; Squarre, D; Madarame, H

    2015-01-01

    A 15-year-old male African lion (Panthera leo) was presented with blindness due to bilateral panuveitis with retinal detachment. Feline coronavirus (FCoV) antigen was identified immunohistochemically in ocular macrophages, consistent with a diagnosis of feline infectious peritonitis (FIP) infection. This is the first report of FIP in an African lion and the first report of ocular FIP in a non-domestic felid.

  14. Impact of sensor failure on the observability of flow dynamics at the Biosphere 2 LEO hillslopes

    NASA Astrophysics Data System (ADS)

    Pasetto, Damiano; Niu, Guo-Yue; Pangle, Luke; Paniconi, Claudio; Putti, Mario; Troch, Peter A.

    2015-12-01

    The Biosphere 2 Landscape Evolution Observatory (LEO) has been developed to investigate hydrological, chemical, biological, and geological processes in a large-scale, controlled infrastructure. The experimental hillslopes at LEO are instrumented with a large number of different sensors that allow detailed monitoring of local and global dynamics and changes in the hydrological state and structure of the landscapes. Sensor failure, i.e., a progressive reduction in the number of active or working sensors, in such an evolving system can have a dramatic impact on observability of flow dynamics and estimation of the model parameters that characterize the soil properties. In this study we assess the retrieval of the spatial distributions of soil water content and saturated hydraulic conductivity under different scenarios of heterogeneity (different values of correlation length of the random field describing the hydraulic conductivity) and a variable number of active sensors. To avoid the influence of model structural errors and measurement bias, the analysis is based on a synthetic representation of the first hydrological experiment at LEO simulated with the physically-based hydrological model CATHY. We assume that the true hydraulic conductivity is a particular random realization of a stochastic field with lognormal distribution and exponential correlation length. During the true run, we collect volumetric water content measurements at an hourly interval. Perturbed observations are then used to estimate the total water storage via linear interpolation and to retrieve the conductivity field via the ensemble Kalman filter technique. The results show that when less than 100 out of 496 total sensors are active, the reconstruction of volumetric water content may introduce large errors in the estimation of total water storage. In contrast, retrieval of the saturated hydraulic conductivity distribution allows the CATHY model to reproduce the integrated hydrological response of

  15. A Search for Stellar Dust Production in Leo P, a Nearby Analog of High Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Boyer, Martha; McDonald, Iain; McQuinn, Kristen; Skillman, Evan; Sonneborn, George; Srinivasan, Sundar; van Loon, Jacco Th.; Zijlstra, Albert; Sloan, Greg

    2016-08-01

    The origin of dust in the early Universe is a matter of debate. One of the main potential dust contributors are Asymptotic Giant Branch (AGB) stars, and several studies have been devoted to investigating whether and how AGB dust production changes in metal-poor environments. Of particular interest are the most massive AGB stars (8-10 Msun), which can in principle enter the dust-producing phase <50 Myr after they form. However, these stars cannot produce their own condensable material (unlike carbon AGB stars), so the efficiency of dust production decreases with metallicity. Evidence for dust production in massive AGB stars more metal-poor than the Magellanic Clouds is scarce due both to the rarity of chemically-unevolved, star-forming systems reachable in the infrared and to the short lifetimes of these stars. The recently discovered galaxy Leo P provides an irresistible opportunity to search for these massive AGB stars: Leo P is a gas-rich, star-forming galaxy, it is nearby enough for resolved star photometry with Spitzer, and its interstellar medium is 0.4 dex more metal-poor than any other accessible star-forming galaxy. Models predict ~3 massive AGB stars may be present in Leo P, and optical HST observations reveal 7 candidates. We propose to use Spitzer to determine whether these stars are dusty, providing valuable constraints to the dust contribution from AGB stars up to at least redshift 3.2, or 11.7 Gyr ago, when massive spheroidals and Galactic globular clusters were still forming. This is a gain of 2.8 Gyr compared to other accessible galaxies. We also request 1 orbit of joint HST time to confirm whether the AGB candidates in Leo P are indeed massive AGB stars belonging to the galaxy. These observations will provide information crucial for potential JWST followup spectroscopy.

  16. Leo Max Davidoff: his formative years and participation in the MacMillan Arctic Expedition.

    PubMed

    Wisoff, Hugh S

    2012-09-01

    Leo Max Davidoff was one of the outstanding students of Harvey Cushing, who helped create the discipline of modern neurological surgery. In his own right, Dr. Davidoff was a pioneer who made significant contributions both in neurosurgery and neuroradiology. He also helped to found the Albert Einstein College of Medicine of Yeshiva University. This paper describes his early life and education, together with his participation in the MacMillan Arctic Expedition of 1925. PMID:22725989

  17. Optimal planning of LEO active debris removal based on hybrid optimal control theory

    NASA Astrophysics Data System (ADS)

    Yu, Jing; Chen, Xiao-qian; Chen, Li-hu

    2015-06-01

    The mission planning of Low Earth Orbit (LEO) active debris removal problem is studied in this paper. Specifically, the Servicing Spacecraft (SSc) and several debris exist on near-circular near-coplanar LEOs. The SSc should repeatedly rendezvous with the debris, and de-orbit them until all debris are removed. Considering the long-duration effect of J2 perturbation, a linear dynamics model is used for each rendezvous. The purpose of this paper is to find the optimal service sequence and rendezvous path with minimum total rendezvous cost (Δv) for the whole mission, and some complex constraints (communication time window constraint, terminal state constraint, and time distribution constraint) should be satisfied meanwhile. Considering this mission as a hybrid optimal control problem, a mathematical model is proposed, as well as the solution method. The proposed approach is demonstrated by a typical active debris removal problem. Numerical experiments show that (1) the model and solution method proposed in this paper can effectively address the planning problem of LEO debris removal; (2) the communication time window constraint and the J2 perturbation have considerable influences on the optimization results; and (3) under the same configuration, some suboptimal sequences are equivalent to the optimal one since their difference in Δv cost is very small.

  18. Phylogeographic Patterns in Africa and High Resolution Delineation of Genetic Clades in the Lion (Panthera leo).

    PubMed

    Bertola, L D; Jongbloed, H; van der Gaag, K J; de Knijff, P; Yamaguchi, N; Hooghiemstra, H; Bauer, H; Henschel, P; White, P A; Driscoll, C A; Tende, T; Ottosson, U; Saidu, Y; Vrieling, K; de Iongh, H H

    2016-08-04

    Comparative phylogeography of African savannah mammals shows a congruent pattern in which populations in West/Central Africa are distinct from populations in East/Southern Africa. However, for the lion, all African populations are currently classified as a single subspecies (Panthera leo leo), while the only remaining population in Asia is considered to be distinct (Panthera leo persica). This distinction is disputed both by morphological and genetic data. In this study we introduce the lion as a model for African phylogeography. Analyses of mtDNA sequences reveal six supported clades and a strongly supported ancestral dichotomy with northern populations (West Africa, Central Africa, North Africa/Asia) on one branch, and southern populations (North East Africa, East/Southern Africa and South West Africa) on the other. We review taxonomies and phylogenies of other large savannah mammals, illustrating that similar clades are found in other species. The described phylogeographic pattern is considered in relation to large scale environmental changes in Africa over the past 300,000 years, attributable to climate. Refugial areas, predicted by climate envelope models, further confirm the observed pattern. We support the revision of current lion taxonomy, as recognition of a northern and a southern subspecies is more parsimonious with the evolutionary history of the lion.

  19. Controlling the Growth of Future LEO Debris Populations with Active Debris Removal

    NASA Technical Reports Server (NTRS)

    Liou, J.-C.; Johnson, N. L.; Hill, N. M.

    2008-01-01

    Active debris removal (ADR) was suggested as a potential means to remediate the low Earth orbit (LEO) debris environment as early as the 1980s. The reasons ADR has not become practical are due to its technical difficulties and the high cost associated with the approach. However, as the LEO debris populations continue to increase, ADR may be the only option to preserve the near-Earth environment for future generations. An initial study was completed in 2007 to demonstrate that a simple ADR target selection criterion could be developed to reduce the future debris population growth. The present paper summarizes a comprehensive study based on more realistic simulation scenarios, including fragments generated from the 2007 Fengyun-1C event, mitigation measures, and other target selection options. The simulations were based on the NASA long-term orbital debris projection model, LEGEND. A scenario, where at the end of mission lifetimes, spacecraft and upper stages were moved to 25-year decay orbits, was adopted as the baseline environment for comparison. Different annual removal rates and different ADR target selection criteria were tested, and the resulting 200-year future environment projections were compared with the baseline scenario. Results of this parametric study indicate that (1) an effective removal strategy can be developed based on the mass and collision probability of each object as the selection criterion, and (2) the LEO environment can be stabilized in the next 200 years with an ADR removal rate of five objects per year.

  20. Effect of LEO cycling on 125 Ah advanced design IPV nickel-hydrogen battery cells

    NASA Technical Reports Server (NTRS)

    Smithrick, John J.; Hall, Stephen W.

    1990-01-01

    An advanced 125 Ah individual pressure vessel (IPV) nickel-hydrogen cell was designed. The primary function of the advanced cell, is to store and deliver energy for long term, low earth-orbit (LEO) spacecraft missions. The new features of this design are: (1) use of 26 percent rather than 31 percent potassium hydroxide (KOH) electrolyte, (2) use of a patented catalyzed wall wick, (3) use of serrated edge separators to facilitate gaseous oxygen and hydrogen flow within the cell, while still maintaining physical contact with the wall wick for electrolyte management, and (4) use of a floating rather than a fixed stack (state-of-the-art) to accommodate nickel electrode expansion. Six 125 Ah flight cells based on this design were fabricated by Eagle-Picher. Three of the cells contain all of the advanced features (test cells) and three are the same as the test cells except they don't have catalyst on the wall wick (control cells). All six cells are in the process of being evaluated in a LEO cycle life test. The cells have accumulated about 4700 LEO cycles (60 percent DOD 10 C). There have been no cell failures, the catalyzed wall wick cells however, are performing better.

  1. Phylogeographic Patterns in Africa and High Resolution Delineation of Genetic Clades in the Lion (Panthera leo)

    PubMed Central

    Bertola, L. D.; Jongbloed, H.; van der Gaag, K. J.; de Knijff, P.; Yamaguchi, N.; Hooghiemstra, H.; Bauer, H.; Henschel, P.; White, P. A.; Driscoll, C. A.; Tende, T.; Ottosson, U.; Saidu, Y.; Vrieling, K.; de Iongh, H. H.

    2016-01-01

    Comparative phylogeography of African savannah mammals shows a congruent pattern in which populations in West/Central Africa are distinct from populations in East/Southern Africa. However, for the lion, all African populations are currently classified as a single subspecies (Panthera leo leo), while the only remaining population in Asia is considered to be distinct (Panthera leo persica). This distinction is disputed both by morphological and genetic data. In this study we introduce the lion as a model for African phylogeography. Analyses of mtDNA sequences reveal six supported clades and a strongly supported ancestral dichotomy with northern populations (West Africa, Central Africa, North Africa/Asia) on one branch, and southern populations (North East Africa, East/Southern Africa and South West Africa) on the other. We review taxonomies and phylogenies of other large savannah mammals, illustrating that similar clades are found in other species. The described phylogeographic pattern is considered in relation to large scale environmental changes in Africa over the past 300,000 years, attributable to climate. Refugial areas, predicted by climate envelope models, further confirm the observed pattern. We support the revision of current lion taxonomy, as recognition of a northern and a southern subspecies is more parsimonious with the evolutionary history of the lion. PMID:27488946

  2. The low-mass classic Algol-type binary UU Leo revisited

    NASA Astrophysics Data System (ADS)

    Yang, Yuan-Gui

    2013-12-01

    New multi-color photometry of the eclipsing binary UU Leo, acquired from 2010 to 2013, was carried out by using the 60-cm and 85-cm telescopes at the Xinglong station, which is administered by National Astronomical Observatories, Chinese Academy of Sciences. With the updated Wilson-Devinney code, the photometric solution was derived from BVR light curves. The results imply that UU Leo is a semi-detached Algol-type binary, with a mass ratio of q = 0.100(±0.002). The change in orbital period was reanalyzed based on all available eclipsing times. The O - C curve could be described by an upward parabola superimposed on a quasi-sinusoidal curve. The period and semi-amplitudes are Pmod = 54.5(±1.1) yr and A = 0.0273d(±0.0015d), which may be attributed to the light-time effect via the presence of an invisible third body. The long-term period increases at a rate of dP/dt = +4.64(±0.14) × 10-7d yr-1, which may be interpreted by the conserved mass being transferred from the secondary to the primary. With mass being transferred, the low-mass Algol-type binary UU Leo may evolve into a binary system with a main sequence star and a helium white dwarf.

  3. Phylogeographic Patterns in Africa and High Resolution Delineation of Genetic Clades in the Lion (Panthera leo).

    PubMed

    Bertola, L D; Jongbloed, H; van der Gaag, K J; de Knijff, P; Yamaguchi, N; Hooghiemstra, H; Bauer, H; Henschel, P; White, P A; Driscoll, C A; Tende, T; Ottosson, U; Saidu, Y; Vrieling, K; de Iongh, H H

    2016-01-01

    Comparative phylogeography of African savannah mammals shows a congruent pattern in which populations in West/Central Africa are distinct from populations in East/Southern Africa. However, for the lion, all African populations are currently classified as a single subspecies (Panthera leo leo), while the only remaining population in Asia is considered to be distinct (Panthera leo persica). This distinction is disputed both by morphological and genetic data. In this study we introduce the lion as a model for African phylogeography. Analyses of mtDNA sequences reveal six supported clades and a strongly supported ancestral dichotomy with northern populations (West Africa, Central Africa, North Africa/Asia) on one branch, and southern populations (North East Africa, East/Southern Africa and South West Africa) on the other. We review taxonomies and phylogenies of other large savannah mammals, illustrating that similar clades are found in other species. The described phylogeographic pattern is considered in relation to large scale environmental changes in Africa over the past 300,000 years, attributable to climate. Refugial areas, predicted by climate envelope models, further confirm the observed pattern. We support the revision of current lion taxonomy, as recognition of a northern and a southern subspecies is more parsimonious with the evolutionary history of the lion. PMID:27488946

  4. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight cells-update 2

    NASA Technical Reports Server (NTRS)

    Smithrick, John J.; Hall, Stephen W.

    1991-01-01

    An update of validation test results confirming the breakthrough in low earth orbit (LEO) cycle life of nickel-hydrogen cells containing 26 percent KOH electrolyte is presented. A breakthrough in the LEO cycle life of individual pressure vessel (IPV nickel-hydrogen cells has been previously reported. The cycle life of boiler plate cells containing 26 percent potassium hydroxide (KOH) electrolyte was about 40 000 LEO cycles compared to 3500 cycles for cells containing 31 percent KOH. This test was conducted at Hughes Aircraft Company under a NASA Lewis contract. The purpose was to investigate the effect of KOH concentration on cycle life. The cycle regime was a stressful accelerated LEO, which consisted of a 27.5 min charge followed by a 17.5 min discharge (2x normal rate). The depth of discharge (DOD) was 80 percent. The cell temperature was maintained at 23 C. The boiler plate test results are in the process of being validated using flight hardware and real time LEO test at the Naval Weapons Support Center (NWSC), Crane, Indiana under a NASA Lewis Contract. Six 48 Ah Hughes recirculation design IPV nickel-hydrogen flight battery cells are being evaluated. Three of the cells contain 26 percent KOH (test cells), and three contain 31 percent KOH (control cells). They are undergoing real time LEO cycle life testing. The cycle regime is a 90-min LEO orbit consisting of a 54-min charge followed by a 36-min discharge. The depth-of-discharge is 80 percent. The cell temperature is maintained at 10 C. The three 31 percent KOH cells failed (cycles 3729, 4165, and 11355). One of the 26 percent KOH cells failed at cycle 15314. The other two 26 percent KOH cells were cycled for over 16600 cycles during the continuing test.

  5. Effect of KOH concentration on LEO cycle life of IPV nickel-hydrogen flight cells-update 2

    NASA Astrophysics Data System (ADS)

    Smithrick, John J.; Hall, Stephen W.

    An update of validation test results confirming the breakthrough in low earth orbit (LEO) cycle life of nickel-hydrogen cells containing 26 percent KOH electrolyte is presented. A breakthrough in the LEO cycle life of individual pressure vessel (IPV nickel-hydrogen cells has been previously reported. The cycle life of boiler plate cells containing 26 percent potassium hydroxide (KOH) electrolyte was about 40 000 LEO cycles compared to 3500 cycles for cells containing 31 percent KOH. This test was conducted at Hughes Aircraft Company under a NASA Lewis contract. The purpose was to investigate the effect of KOH concentration on cycle life. The cycle regime was a stressful accelerated LEO, which consisted of a 27.5 min charge followed by a 17.5 min discharge (2x normal rate). The depth of discharge (DOD) was 80 percent. The cell temperature was maintained at 23 C. The boiler plate test results are in the process of being validated using flight hardware and real time LEO test at the Naval Weapons Support Center (NWSC), Crane, Indiana under a NASA Lewis Contract. Six 48 Ah Hughes recirculation design IPV nickel-hydrogen flight battery cells are being evaluated. Three of the cells contain 26 percent KOH (test cells), and three contain 31 percent KOH (control cells). They are undergoing real time LEO cycle life testing. The cycle regime is a 90-min LEO orbit consisting of a 54-min charge followed by a 36-min discharge. The depth-of-discharge is 80 percent. The cell temperature is maintained at 10 C. The three 31 percent KOH cells failed (cycles 3729, 4165, and 11355). One of the 26 percent KOH cells failed at cycle 15314. The other two 26 percent KOH cells were cycled for over 16600 cycles during the continuing test.

  6. A SCUBA-2 survey of FeLoBAL QSOs. Are FeLoBALs in a `transition phase' between ULIRGs and QSOs?

    NASA Astrophysics Data System (ADS)

    Violino, Giulio; Coppin, Kristen E. K.; Stevens, Jason A.; Farrah, Duncan; Geach, James E.; Alexander, Dave M.; Hickox, Ryan; Smith, Daniel J. B.; Wardlow, Julie L.

    2016-04-01

    It is thought that a class of broad absorption line (BAL) QSOs, characterized by Fe absorption features in their UV spectra (called `FeLoBALs'), could mark a transition stage between the end of an obscured starburst event and a youthful QSO beginning to shed its dust cocoon, where Fe has been injected into the interstellar medium by the starburst. To test this hypothesis, we have undertaken deep Submillimetre Common-User Bolometer Array 2 (SCUBA-2) 850 μm observations of a sample of 17 FeLoBAL QSOs with 0.89 ≤ z ≤ 2.78 and -23.31 ≤ MB ≤ -28.50 to directly detect an excess in the thermal emission of the dust which would probe enhanced star formation activity. We find that FeLoBALs are not luminous sources in the sub-mm, none of them are individually detected at 850 μm, nor as a population through stacking (Fs = 1.14 ± 0.58 mJy). Statistical and survival analyses reveal that FeLoBALs have sub-mm properties consistent with BAL and non-BAL QSOs with matched redshifts and magnitudes. An Spectral Energy Distribution fitting analysis shows that the far-infrared emission is dominated by active galactic nuclei activity, and a starburst component is required only in 6/17 sources of our sample; moreover the integrated total luminosity of 16/17 sources is L ≥ 1012 L⊙, high enough to classify FeLoBALs as infrared luminous. In conclusion, we do not find any evidence in support of FeLoBAL QSOs being a transition population between an ultraluminous infrared galaxy (ULIRG) and an unobscured QSO; in particular, FeLoBALs are not characterized by a cold starburst which would support this hypothesis.

  7. ALFALFA Discovery of the Nearby Gas-rich Dwarf Galaxy Leo P. IV. Distance Measurement from LBT Optical Imaging

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen B. W.; Skillman, Evan D.; Berg, Danielle; Cannon, John M.; Salzer, John J.; Adams, Elizabeth A. K.; Dolphin, Andrew; Giovanelli, Riccardo; Haynes, Martha P.; Rhode, Katherine L.

    2013-12-01

    Leo P is a low-luminosity dwarf galaxy discovered through the blind H I Arecibo Legacy Fast ALFA survey. The H I and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with both active star formation and an underlying older population, as well as an extremely low oxygen abundance. Here, we measure the distance to Leo P by applying the tip of the red giant branch (TRGB) distance method to photometry of the resolved stellar population from new Large Binocular Telescope V and I band imaging. We measure a distance modulus of 26.19^{+0.17}_{-0.50} mag corresponding to a distance of 1.72^{+0.14}_{-0.40} Mpc. Although our photometry reaches 3 mag below the TRGB, the sparseness of the red giant branch yields higher uncertainties on the lower limit of the distance. Leo P is outside the Local Group with a distance and velocity consistent with the local Hubble flow. While located in a very low-density environment, Leo P lies within ~0.5 Mpc of a loose association of dwarf galaxies which include NGC 3109, Antlia, Sextans A, and Sextans B, and 1.1 Mpc away from its next nearest neighbor, Leo A. Leo P is one of the lowest metallicity star-forming galaxies known in the nearby universe, comparable in metallicity to I Zw 18 and DDO 68, but with stellar characteristics similar to dwarf spheriodals (dSphs) in the Local Volume such as Carina, Sextans, and Leo II. Given its physical properties and isolation, Leo P may provide an evolutionary link between gas-rich dwarf irregular galaxies and dSphs that have fallen into a Local Group environment and been stripped of their gas. Based on observations made with the Large Binocular Telescope (LBT) Observatory. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max

  8. Resonant tunnelling diode oscillator as an alternative LO for SIS receiver applications

    NASA Technical Reports Server (NTRS)

    Blundell, R.; Papa, D. C.; Brown, E. R.; Parker, C. D.

    1993-01-01

    The resonant tunnelling diode (RTD) oscillator has been demonstrated for the first time as a local oscillator (LO) in a heterodyne receiver. Noise measurements made on a sensitive 200 GHz superconductor-insulator-superconductor receiver using both a multiplied Gunn diode and an RTD oscillator as the LO revealed no difference in receiver noise as a function of oscillator type.

  9. A ROACH Based Data Acquisition System for the Low Frequency All Sky Monitor (LoFASM)

    NASA Astrophysics Data System (ADS)

    Dartez, Louis P.; Jenet, F.; Cohen, S.; Creighton, T. D.; Ford, A.; Garcia, A.; Hicks, B.; Hinojosa, J.; Kassim, N. E.; Longoria, C.; Lunsford, G.; Mata, A.; Miller, R. B.; Price, R. H.; Quintero, L.; Ray, P. S.; Reser, J.; Rivera, J.; Stovall, K.; Taylor, G. B.

    2013-01-01

    The Low Frequency All Sky Monitor (LoFASM) is a distributed array of dipole antennas that are sensitive to radio frequencies from 5 to 88 MHz. The primary science goals will be the detection and study of low-frequency radio transients. LoFASM consists of antennas and front end electronics that were originally developed for the Long Wavelength Array (LWA) by the U.S. Naval Research Lab, the University of New Mexico, Virginia Tech, and the Jet Propulsion Laboratory. LoFASM, funded by the U.S. Department of Defense, will initially consist of 4 stations, each consisting of 12 dual-polarization dipole antenna stands. The signals received by LoFASM are digitized and processed using Reconfigurable Open Architecture Computing Hardware (ROACH) boards. This poster will describe the LoFASM project with an emphasis on the ROACH data processing pipe-line.

  10. HERRO: A Science-Oriented Strategy for Crewed Missions Beyond LEO

    NASA Technical Reports Server (NTRS)

    Schmidt, George R.

    2011-01-01

    This paper presents an exploration strategy for human missions beyond Low Earth Orbit (LEO) and the Moon that combines the best features of human and robotic spaceflight. This "Human Exploration using Real-time Robotic Operations" (HERRO) strategy refrains from placing humans on the surfaces of the Moon and Mars in the near-term. Rather, it focuses on sending piloted spacecraft and crews into orbit around exploration targets of interest, such as Mars, and conducting astronaut exploration of the surfaces using telerobots and remotely controlled systems. By eliminating the significant communications delay with Earth due to the speed of light limit, teleoperation provides scientists real-time control of rovers and other sophisticated instruments, in effect giving them a "virtual presence" on planetary surfaces, and thus expanding the scientific return at these destinations. It also eliminates development of the numerous man-rated landers, ascent vehicles and surface systems that are required to land humans on planetary surfaces. The propulsive requirements to travel from LEO to many destinations with shallow gravity-wells in the inner solar system are quite similar. Thus, a single spacecraft design could perform a variety of missions, including orbit-based surface exploration of the Moon, Mars and Venus, and rendezvous with Near Earth Asteroids (NEAs), as well as Phobos and Deimos. Although HERRO bypasses many of the initial steps that have been historically associated with human space exploration, it opens the door to many new destinations that are candidates for future resource utilization and settlement. HERRO is a first step that takes humans to exciting destinations beyond LEO, while expanding the ability to conduct science within the inner solar system.

  11. On the feasibility of phase only PPP for kinematic LEO orbits

    NASA Astrophysics Data System (ADS)

    Wallat, Christoph; Schön, Steffen

    2016-04-01

    Low Earth Orbiters (LEO) are satellites in altitudes up to 1000 kilometers. From the sensor data collected on board the Earth's gravity field can be recovered. Over the last 15 years several satellite missions were brought into space and the orbit determination improved over the years. To process the sensor data, precise positioning and timing of the satellite is mandatory. There are two approaches for precise orbit determination (POD) of LEO satellites. Kinematic orbits are based on GNSS observations and star camera data measured on board of the LEO. With a Precise Point Positioning (PPP) known from the terrestrial case, using ionospheric-free linear combinations P3 and L3 three-dimensional coordinates of the LEO can be estimated for every observation epoch. To counteract the challenges in kinematic orbit determination our approach is based on a technique called GNSS receiver clock modeling (RCM). Here the frequency stability of an external oscillator is used to model the behavior of the GNSS receiver clock with piecewise linear polynomials instead of estimating epoch-wise the receiver clock time offset as an unknown parameter. When using RCM the observation geometry is stabilized and the orbit coordinates and the receiver clock error can be estimated with a better precision. The satellites of the Gravity Recovery And Climate Experiment (GRACE) mission are equipped with Ultra Stable quartz Oscillators (USO). The USO frequency stability is used to correct the GRACE GPS receiver clock. Therefore, receiver clock modeling is feasible for polynomials with a length up to 60 seconds, leading to improved mean PDOP values of 30 % and smaller formal mean standard deviations of the coordinates between 6 and 33 %. We developed a new approach for GRACE orbits using kinematic PPP with clock modeling and tested our approach with simulated and real GPS data. The idea to use only carrier phase observations in the final processing and no code measurements leads to a reduced number

  12. Leo Kanner's Mention of 1938 in His Report on Autism Refers to His First Patient.

    PubMed

    Olmsted, Dan; Blaxill, Mark

    2016-01-01

    Leo Kanner begins his landmark 1943 case series on autistic children by stating the condition was first brought to his attention in 1938. Recent letters to JADD have described this reference as "mysterious" and speculated it refers to papers published that year by Despert or Asperger. In fact, as Kanner goes on to state, 1938 is when he examined the first child in his case series. An exchange of letters with Despert and later writing by Kanner also point to the originality of his observations. PMID:26231203

  13. Leo Kanner's Mention of 1938 in His Report on Autism Refers to His First Patient.

    PubMed

    Olmsted, Dan; Blaxill, Mark

    2016-01-01

    Leo Kanner begins his landmark 1943 case series on autistic children by stating the condition was first brought to his attention in 1938. Recent letters to JADD have described this reference as "mysterious" and speculated it refers to papers published that year by Despert or Asperger. In fact, as Kanner goes on to state, 1938 is when he examined the first child in his case series. An exchange of letters with Despert and later writing by Kanner also point to the originality of his observations.

  14. Low-Earth-Orbit (LEO) Life Cycle Evaluation of Nickel-Zinc Batteries

    NASA Technical Reports Server (NTRS)

    Coates, D.; Ferreira, E.; Nyce, M.; Charkey, A.

    1997-01-01

    The conclusion of the Low-Earth-Orbit (LEO) life cycle evaluation of nickel-zinc batteries are: that composite nickel electrode provide excellent performance at a reduced weight and lower cost; calcium / zinc electrode minimizes shape change; unioptimized cell designs yield 60 Wh/kg; nickel-zinc delivers 600 cycles at 80% DOD; long cycle life obtainable at low DOD; high rate capability power density; long-term failure mechanism is stack dry; and anomalous overcharge (1120%) greatly affected cell performance but did not induce failure and was recoverable.

  15. Measurements of Multi-star Systems LEO 5 and MKT 13

    NASA Astrophysics Data System (ADS)

    AlZaben, Faisal; Priest, Allen; Priest, Stephen; Qiu, Rex; Boyce, Grady; Boyce, Pat

    2016-04-01

    We report measurements of the position angles and separations of two multi-star systems observed during the fall of 2015. Image data was obtained using an online 17-inch iTelescope system in Nerpio, Spain. Image data was analyzed using Maxim DL Pro 6 and Mira Pro x64 software tools at the Army and Navy Academy in Carlsbad, California. Our measurements of the LEO 5 system are consistent with historical data, although inconclusive as to the nature of the system. Our measurements and the historical data for the MKT 13 system show a consistent linearity in the position angle and separation.

  16. Tanker Argus: Re-supply for a LEO Cryogenic Propellant Depot

    NASA Astrophysics Data System (ADS)

    St. Germain, B.; Olds, J.; Kokan, T.; Marcus, L.; Miller, J.

    The Argus reusable launch vehicle (RLV) concept is a single-stage-to-orbit conical, winged bodied vehicle powered by two liquid hydrogen/liquid oxygen supercharged ejector ramjets. The 3rd generation Argus launch vehicle utilizes advanced vehicle technologies along with a Maglev launch assist track. A tanker version of the Argus RLV is envisioned to provide an economical means of providing liquid fuel and oxidizer to an orbiting low-Earth orbit (LEO) propellant depot. This depot could then provide propellant to various spacecraft, including reusable orbital transfer vehicles used to ferry space solar power satellites to geo-stationary orbit. Two different tanker Argus configurations were analyzed. The first simply places additional propellant tanks inside the payload bay of an existing Argus reusable launch vehicle. The second concept is a modified Argus RLV in which the payload bay is removed and the vehicle propellant tanks are stretched to hold extra propellant. An iterative conceptual design process was used to design both Argus vehicles. This process involves various disciplines including aerodynamics, trajectory analysis, weights &structures, propulsion, operations, safety, and cost/economics. The payload bay version of tanker Argus, which has a gross mass of 256.3MT, is designed to deliver a 9.07MT payload to LEO. This payload includes propellant and the tank structure required to secure this propellant in the payload bay. The modified, pure tanker version of Argus has a gross mass of 218.6MT and is sized to deliver a full 9.07MT of propellant to LEO. The economic analysis performed for this study involved the calculation of many factors including the design/development and recurring costs of each vehicle. These results were used along with other economic assumptions to determine the "per kilogram" cost of delivering propellant to orbit. The results show that for a given flight rate the "per kilogram" cost is cheaper for the pure tanker version of Argus

  17. Re-Entry Point Targeting for LEO Spacecraft using Aerodynamic Drag

    NASA Technical Reports Server (NTRS)

    Omar, Sanny; Bevilacqua, Riccardo; Fineberg, Laurence; Treptow, Justin; Johnson, Yusef; Clark, Scott

    2016-01-01

    Most Low Earth Orbit (LEO) spacecraft do not have thrusters and re-enter atmosphere in random locations at uncertain times. Objects pose a risk to persons, property, or other satellites. Has become a larger concern with the recent increase in small satellites. Working on a NASA funded project to design a retractable drag device to expedite de-orbit and target a re-entry location through modulation of the drag area. Will be discussing the re-entry point targeting algorithm here.

  18. Commentary: Science, Technology, and Society in Guidelines for Using Technology to Prepare Social Studies Teachers--A Reply to Hicks et al. and Crocco and Leo

    ERIC Educational Resources Information Center

    Mason, Lance

    2015-01-01

    This essay is a response to both the "Guidelines for Using Technology to Prepare Social Studies Teachers" published in this journal by Hicks, Lee, Berson, Bolick, and Diem (2014) and the rejoinder by Crocco and Leo (2015). The author agrees with Crocco and Leo's assessment that removing the principal regarding science, technology, and…

  19. ALFALFA Discovery of the Nearby Gas-rich Dwarf Galaxy Leo P. V. Neutral Gas Dynamics and Kinematics

    NASA Astrophysics Data System (ADS)

    Bernstein-Cooper, Elijah Z.; Cannon, John M.; Elson, Edward C.; Warren, Steven R.; Chengular, Jayaram; Skillman, Evan D.; Adams, Elizabeth A. K.; Bolatto, Alberto D.; Giovanelli, Riccardo; Haynes, Martha P.; McQuinn, Kristen B. W.; Pardy, Stephen A.; Rhode, Katherine L.; Salzer, John J.

    2014-08-01

    We present new H I spectral line imaging of the extremely metal-poor, star-forming dwarf irregular galaxy Leo P. Our H I images probe the global neutral gas properties and the local conditions of the interstellar medium (ISM). The H I morphology is slightly elongated along the optical major axis. We do not find obvious signatures of interaction or infalling gas at large spatial scales. The neutral gas disk shows obvious rotation, although the velocity dispersion is comparable to the rotation velocity. The rotation amplitude is estimated to be V c =15 ± 5 km s-1. Within the H I radius probed by these observations, the mass ratio of gas to stars is roughly 2:1, while the ratio of the total mass to the baryonic mass is gsim15:1. We use this information to place Leo P on the baryonic Tully-Fisher relation, testing the baryonic content of cosmic structures in a sparsely populated portion of parameter space that has hitherto been occupied primarily by dwarf spheroidal galaxies. We detect the signature of two temperature components in the neutral ISM of Leo P the cold and warm components have characteristic velocity widths of 4.2 ± 0.9 km s-1 and 10.1 ± 1.2 km s-1, corresponding to kinetic temperature upper limits of ~1100 K and ~6200 K, respectively. The cold H I component is unresolved at a physical resolution of 200 pc. The highest H I surface densities are observed in close physical proximity to the single H II region. A comparison of the neutral gas properties of Leo P with other extremely metal-deficient (XMD) galaxies reveals that Leo P has the lowest neutral gas mass of any known XMD, and that the dynamical mass of Leo P is more than two orders of magnitude smaller than any known XMD with comparable metallicity.

  20. Contrast Invariant Interest Point Detection by Zero-Norm LoG Filter.

    PubMed

    Zhenwei Miao; Xudong Jiang; Kim-Hui Yap

    2016-01-01

    The Laplacian of Gaussian (LoG) filter is widely used in interest point detection. However, low-contrast image structures, though stable and significant, are often submerged by the high-contrast ones in the response image of the LoG filter, and hence are difficult to be detected. To solve this problem, we derive a generalized LoG filter, and propose a zero-norm LoG filter. The response of the zero-norm LoG filter is proportional to the weighted number of bright/dark pixels in a local region, which makes this filter be invariant to the image contrast. Based on the zero-norm LoG filter, we develop an interest point detector to extract local structures from images. Compared with the contrast dependent detectors, such as the popular scale invariant feature transform detector, the proposed detector is robust to illumination changes and abrupt variations of images. Experiments on benchmark databases demonstrate the superior performance of the proposed zero-norm LoG detector in terms of the repeatability and matching score of the detected points as well as the image recognition rate under different conditions.

  1. TriLoNet: Piecing Together Small Networks to Reconstruct Reticulate Evolutionary Histories.

    PubMed

    Oldman, James; Wu, Taoyang; van Iersel, Leo; Moulton, Vincent

    2016-08-01

    Phylogenetic networks are a generalization of evolutionary trees that can be used to represent reticulate processes such as hybridization and recombination. Here, we introduce a new approach called TriLoNet (Trinet Level- one Network algorithm) to construct such networks directly from sequence alignments which works by piecing together smaller phylogenetic networks. More specifically, using a bottom up approach similar to Neighbor-Joining, TriLoNet constructs level-1 networks (networks that are somewhat more general than trees) from smaller level-1 networks on three taxa. In simulations, we show that TriLoNet compares well with Lev1athan, a method for reconstructing level-1 networks from three-leaved trees. In particular, in simulations we find that Lev1athan tends to generate networks that overestimate the number of reticulate events as compared with those generated by TriLoNet. We also illustrate TriLoNet's applicability using simulated and real sequence data involving recombination, demonstrating that it has the potential to reconstruct informative reticulate evolutionary histories. TriLoNet has been implemented in JAVA and is freely available at https://www.uea.ac.uk/computing/TriLoNet.

  2. LoCoH: Nonparameteric Kernel Methods for Constructing Home Ranges and Utilization Distributions

    PubMed Central

    Getz, Wayne M.; Fortmann-Roe, Scott; Wilmers, Christopher C.

    2007-01-01

    Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: “fixed sphere-of-influence,” or r-LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an “adaptive sphere-of-influence,” or a-LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a), and compare them to the original “fixed-number-of-points,” or k-LoCoH (all kernels constructed from k-1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a-LoCoH is generally superior to k- and r-LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu). PMID:17299587

  3. LoCoH: Non-parameteric kernel methods for constructing home ranges and utilization distributions

    USGS Publications Warehouse

    Getz, Wayne M.; Fortmann-Roe, Scott; Cross, Paul C.; Lyons, Andrew J.; Ryan, Sadie J.; Wilmers, Christopher C.

    2007-01-01

    Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: ‘‘fixed sphere-of-influence,’’ or r -LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an ‘‘adaptive sphere-of-influence,’’ or a -LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a ), and compare them to the original ‘‘fixed-number-of-points,’’ or k -LoCoH (all kernels constructed from k -1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a -LoCoH is generally superior to k - and r -LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu).

  4. LoCoH: nonparameteric kernel methods for constructing home ranges and utilization distributions.

    PubMed

    Getz, Wayne M; Fortmann-Roe, Scott; Cross, Paul C; Lyons, Andrew J; Ryan, Sadie J; Wilmers, Christopher C

    2007-02-14

    Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: "fixed sphere-of-influence," or r-LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an "adaptive sphere-of-influence," or a-LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a), and compare them to the original "fixed-number-of-points," or k-LoCoH (all kernels constructed from k-1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a-LoCoH is generally superior to k- and r-LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu).

  5. Recent Progress on the Second Generation CMORPH: LEO-IR Based Precipitation Estimates and Cloud Motion Vector

    NASA Astrophysics Data System (ADS)

    Xie, Pingping; Joyce, Robert; Wu, Shaorong

    2015-04-01

    As reported at the EGU General Assembly of 2014, a prototype system was developed for the second generation CMORPH to produce global analyses of 30-min precipitation on a 0.05olat/lon grid over the entire globe from pole to pole through integration of information from satellite observations as well as numerical model simulations. The second generation CMORPH is built upon the Kalman Filter based CMORPH algorithm of Joyce and Xie (2011). Inputs to the system include rainfall and snowfall rate retrievals from passive microwave (PMW) measurements aboard all available low earth orbit (LEO) satellites, precipitation estimates derived from infrared (IR) observations of geostationary (GEO) as well as LEO platforms, and precipitation simulations from numerical global models. Key to the success of the 2nd generation CMORPH, among a couple of other elements, are the development of a LEO-IR based precipitation estimation to fill in the polar gaps and objectively analyzed cloud motion vectors to capture the cloud movements of various spatial scales over the entire globe. In this presentation, we report our recent work on the refinement for these two important algorithm components. The prototype algorithm for the LEO IR precipitation estimation is refined to achieve improved quantitative accuracy and consistency with PMW retrievals. AVHRR IR TBB data from all LEO satellites are first remapped to a 0.05olat/lon grid over the entire globe and in a 30-min interval. Temporally and spatially co-located data pairs of the LEO TBB and inter-calibrated combined satellite PMW retrievals (MWCOMB) are then collected to construct tables. Precipitation at a grid box is derived from the TBB through matching the PDF tables for the TBB and the MWCOMB. This procedure is implemented for different season, latitude band and underlying surface types to account for the variations in the cloud - precipitation relationship. At the meantime, a sub-system is developed to construct analyzed fields of

  6. Higgs boson gluon-fusion production beyond threshold in N3LO QCD

    DOE PAGES

    Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard

    2015-03-18

    In this study, we compute the gluon fusion Higgs boson cross-section at N3LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N3LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N3LO in perturbative QCD.

  7. The Komplast Experiment: Space Environmental Effects after 12 Years in LEO (and Counting)

    NASA Technical Reports Server (NTRS)

    Shaevich, Sergei K.; Aleksandrov, Nicholai G.; Shumov, Andrei E.; Novikov, L. S.; Alred, John A.; Shindo, David J.; Kravchenko, Michael; Golden, Johnny L.

    2014-01-01

    The Komplast materials experiment was designed by the Khrunichev Space Center, together with other Russian scientific institutes, and has been carried out by Mission Control Moscow since 1998. The purpose is to study the effect of the low earth orbit (LEO) environment on exposed samples of various spacecraft materials. The Komplast experiment began with the launch of the first International Space Station (ISS) module on November 20, 1998. Two of eight experiment panels were retrieved during Russian extravehicular activity in February 2011 after 12 years of LEO exposure, and were subsequently returned to Earth by Space Shuttle "Discovery" on the STS-133/ULF-5 mission. The retrieved panels contained an experiment to detect micrometeoroid and orbital debris (MMOD) impacts, radiation sensors, a temperature sensor, several pieces of electrical cable, both carbon composite and adhesive-bonded samples, and many samples made from elastomeric and fluoroplastic materials. Our investigation is complete and a summary of the results obtained from this uniquely long-duration exposure experiment will be presented.

  8. Real-Time Optical Surveillance of LEO/MEO with Small Telescopes

    NASA Astrophysics Data System (ADS)

    Zimmer, P.; McGraw, J.; Ackermann, M.

    J.T. McGraw and Associates, LLC operates two proof-of-concept wide-field imaging systems to test novel techniques for uncued surveillance of LEO/MEO/GEO and, in collaboration with the University of New Mexico (UNM), uses a third small telescope for rapidly queued same-orbit follow-up observations. Using our GPU-accelerated detection scheme, the proof-of-concept systems operating at sites near and within Albuquerque, NM, have detected objects fainter than V=13 at greater than 6 sigma significance. This detection approximately corresponds to a 16 cm object with albedo of 0.12 at 1000 km altitude. Dozens of objects are measured during each operational twilight period, many of which have no corresponding catalog object. The two proof-of-concept systems, separated by ~30km, work together by taking simultaneous images of the same orbital volume to constrain the orbits of detected objects using parallax measurements. These detections are followed-up by imaging photometric observations taken at UNM to confirm and further constrain the initial orbit determination and independently assess the objects and verify the quality of the derived orbits. This work continues to demonstrate that scalable optical systems designed for real-time detection of fast moving objects, which can be then handed off to other instruments capable of tracking and characterizing them, can provide valuable real-time surveillance data at LEO and beyond, which substantively informs the SSA process.

  9. LEGEND - a three-dimensional LEO-to-GEO debris evolutionary model

    NASA Astrophysics Data System (ADS)

    Liou, J.-C.; Hall, D. T.; Krisko, P. H.; Opiela, J. N.

    2004-01-01

    A new orbital debris evolutionary model is being developed by the NASA Orbital Debris Program Office at Johnson Space Center. LEGEND, a LEO-to-GEO Environment Debris model, is capable of reproducing the historical debris environment as well as performing future debris environment projection. The model covers the near Earth space between 200 and 40,000 km altitude and outputs debris distributions in one-dimensional (altitude), two-dimensional (altitude, latitude), and three-dimensional (altitude, latitude, longitude) formats. LEGEND is a three-year (2001-2003) project. The historical part of the model has been completed and the future projection part is being developed/tested. The model utilizes a recently updated historical satellite launch database, two efficient and accurate propagators, and a new NASA satellite breakup model. This paper summarizes the justifications for building a full-scale three-dimensional debris evolutionary model, the overall model structure, and several key components of the model. Preliminary model predictions of debris distributions in the Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geosynchronous Earth Orbit (GEO) regions are presented.

  10. LEGEND - A three-dimensional LEO-to-GEO debris evolution model

    NASA Astrophysics Data System (ADS)

    Liou, J.; Anz-Meador, P.; Hall, D.; Krisko, P.; Opiela, J.

    A new orbital debris evolution model is being developed by the NASA Orbital Debris Program Office at Johnson Space Center. LEGEND, a LEO-to-GEO Environment Debris model, is capable of reproducing the historical debris environment as well as performing future debris environment projection. The model covers the near Earth space between 200 and 50,000 km altitude and outputs debris distributions in 1 D (altitude), 2 D (altitude, latitude), and 3-D (altitude, latitude,-- longitude) formats. LEGEND is a three-year project. The historical part of the model has been completed and the future projection part is being developed/tested. The model utilizes a recently updated historical satellite launch database, two efficient and accurate propagators, and a new NASA satellite breakup model. This paper summarizes the justifications for building a full-scale 3-D debris evolution model, the overall model structure, and several key components of the model. Preliminary model predictions of debris distributions in the Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geosynchronous Earth Orbit (GEO) regions will be presented.

  11. Data analysis and interpretation related to space system/environment interactions at LEO altitude

    NASA Technical Reports Server (NTRS)

    Raitt, W. John; Schunk, Robert W.

    1991-01-01

    Several studies made on the interaction of active systems with the LEO space environment experienced from orbital or suborbital platforms are covered. The issue of high voltage space interaction is covered by theoretical modeling studies of the interaction of charged solar cell arrays with the ionospheric plasma. The theoretical studies were complemented by experimental measurements made in a vacuum chamber. The other active system studied was the emission of effluent from a space platform. In one study the emission of plasma into the LEO environment was studied by using initially a 2-D model, and then extending this model to 3-D to correctly take account of plasma motion parallel to the geomagnetic field. The other effluent studies related to the releases of neutral gas from an orbiting platform. One model which was extended and used determined the density, velocity, and energy of both an effluent gas and the ambient upper atmospheric gases over a large volume around the platform. This model was adapted to study both ambient and contaminant distributions around smaller objects in the orbital frame of reference with scale sizes of 1 m. The other effluent studies related to the interaction of the released neutral gas with the ambient ionospheric plasma. An electrostatic model was used to help understand anomalously high plasma densities measured at times in the vicinity of the space shuttle orbiter.

  12. A Parametric Study on Using Active Debris Removal to Stabilize the Future LEO Debris Environment

    NASA Technical Reports Server (NTRS)

    Liou, J.C.

    2010-01-01

    Recent analyses of the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited the interest in using active debris removal (ADR) to remediate the environment. There are; however, monumental technical, resources, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of the effectiveness of ADR must be conducted. The goal is to demonstrate the feasibility of using ADR to preserve the future environment and to guide its implementation to maximize the benefit-cost ratio. This paper describes a comprehensive sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term, orbital debris evolutionary model, LEGEND, is used to quantify the effects of many key parameters. These parameters include (1) the starting epoch of ADR implementation, (2) various target selection criteria, (3) the benefits of collision avoidance maneuvers, (4) the consequence of targeting specific inclination or altitude regimes, (5) the consequence of targeting specific classes of vehicles, and (6) the timescale of removal. Additional analyses on the importance of postmission disposal and how future launches might affect the requirements to stabilize the environment are also included.

  13. Space environmental effects on spacecraft: LEO materials selection guide, part 2

    NASA Technical Reports Server (NTRS)

    Silverman, Edward M.

    1995-01-01

    This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 2 covers thermal control systems, power systems, optical components, electronic systems, and applications.

  14. DETECTION OF A GIANT EXTRASOLAR PLANET ORBITING THE ECLIPSING POLAR DP LEO

    SciTech Connect

    Qian, S.-B.; Liao, W.-P.; Zhu, L.-Y.; Dai, Z.-B.

    2010-01-01

    DP Leo is the first discovered eclipsing polar with a short period of 1.4967 hours. The period variation of the eclipsing binary was analyzed by using five new determined eclipse times together with those compiled from the literature. It is discovered that the O - C curve of DP Leo shows a cyclic variation with a period of 23.8 years and a semiamplitude of 31.5 s. The small-amplitude periodic change can be plausibly explained as the light-travel time effect due to the presence of a tertiary companion. The mass of the tertiary component is determined to be M {sub 3}sin i' = 0.00600({+-}0.00055) M {sub sun} = 6.28({+-}0.58) M {sub Jupiter} when a total mass of 0.69 M {sub sun} is adopted. If the tertiary companion is coplanar to the eclipsing binary (i.e., i' = 79.{sup 0}5), it should be a giant extrasolar planet with a mass of 6.39 M {sub Jupiter} at a distance of 8.6 astronomical units to the central binary. One of the most interesting things that we have learned about extrasolar planets over the last 17 years is that they can exist almost anywhere. The detection of a giant planet orbiting a polar would provide insight into the formation and evolution of circumbinary planets (planets orbiting both components of short-period binaries) as well as the late evolution of binary stars.

  15. Early Miocene granitoids from the Leo Pargil gneiss dome, northwest Himalaya

    NASA Astrophysics Data System (ADS)

    Hassett, W.; Leech, M. L.

    2007-12-01

    The Leo Pargil gneiss dome is comprised of upper amphibolite-facies metasedimentary rocks of the lower Tethyan Himalayan sequence (known as the Haimantas Group), that are intruded by numerous small granitoid bodies and leucogranite dikes. The dome is located in northern India/southwestern Tibet at the junction of the Sutlej and Spiti rivers, west of the Zada basin. U-Pb SHRIMP dating of zircon yield concordant ages ranging from Late Archean to Late Proterozoic for paragneisses (2.6 Ga to 970 Ma) corresponding to the Haimantas group, and Early Oligocene to Middle Miocene ages for granitoid intrusions (33 Ma to 15 Ma). Concordant analyses and lower intercept ages from Tera-Wasserburg concordia plots range from 28.1-17.2 Ma. Late Oligocene to Early Miocene ages are from zircon domains with consistently high U contents (1500 to over 25000 ppm). Linear regression of age vs. U content scatter plots show a trend toward younger ages (22-20 Ma) corresponding to ages from zircon with lower U contents (1000-3000 ppm) and that is consistent with lower intercept ages. These Early Miocene ages for Leo Pargil granitoids correspond to the ages for the widespread leucogranite bodies exposed throughout the Himalaya and granites from the North Himalayan gneiss domes further east.

  16. Minimum Number of Observation Points for LEO Satellite Orbit Estimation by OWL Network

    NASA Astrophysics Data System (ADS)

    Park, Maru; Jo, Jung Hyun; Cho, Sungki; Choi, Jin; Kim, Chun-Hwey; Park, Jang-Hyun; Yim, Hong-Suh; Choi, Young-Jun; Moon, Hong-Kyu; Bae, Young-Ho; Park, Sun-Youp; Kim, Ji-Hye; Roh, Dong-Goo; Jang, Hyun-Jung; Park, Young-Sik; Jeong, Min-Ji

    2015-12-01

    By using the Optical Wide-field Patrol (OWL) network developed by the Korea Astronomy and Space Science Institute (KASI) we generated the right ascension and declination angle data from optical observation of Low Earth Orbit (LEO) satellites. We performed an analysis to verify the optimum number of observations needed per arc for successful estimation of orbit. The currently functioning OWL observatories are located in Daejeon (South Korea), Songino (Mongolia), and Oukaïmeden (Morocco). The Daejeon Observatory is functioning as a test bed. In this study, the observed targets were Gravity Probe B, COSMOS 1455, COSMOS 1726, COSMOS 2428, SEASAT 1, ATV-5, and CryoSat-2 (all in LEO). These satellites were observed from the test bed and the Songino Observatory of the OWL network during 21 nights in 2014 and 2015. After we estimated the orbit from systematically selected sets of observation points (20, 50, 100, and 150) for each pass, we compared the difference between the orbit estimates for each case, and the Two Line Element set (TLE) from the Joint Space Operation Center (JSpOC). Then, we determined the average of the difference and selected the optimal observation points by comparing the average values.

  17. Space environmental effects on spacecraft: LEO materials selection guide, part 1

    NASA Technical Reports Server (NTRS)

    Silverman, Edward M.

    1995-01-01

    This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 1 covers spacecraft design considerations for the space environment; advanced composites; polymers; adhesives; metals; ceramics; protective coatings; and lubricants, greases, and seals.

  18. Observation angle and plane characterisation for ISAR imaging of LEO space objects

    NASA Astrophysics Data System (ADS)

    Chen, Jin; Fu, Tuo; Chen, Defeng; Gao, Meiguo

    2016-07-01

    For inverse synthetic aperture radar (ISAR) imaging of low Earth orbit (LEO) space objects, examining the variations in the image plane of the object over the entire visible arc period allows more direct characterisation of the variations in the object imaging. In this study, the ideal turntable model was extended to determine the observation geometry of near-circular LEO objects. Two approximations were applied to the observation model to calculate the image plane's normal and observation angles for near-circular orbit objects. One approximation treats the orbit of the space object as a standard arc relative to the Earth during the radar observation period, and the other omits the effect of the rotation of the Earth on the observations. First, the closed-form solution of the image plane normal in various attitude-stabilisation approaches was determined based on geometric models. The characteristics of the image plane and the observation angle of the near-circular orbit object were then analysed based on the common constraints of the radar line-of-sight (LOS). Subsequently, the variations in the image plane and the geometric constraints of the ISAR imaging were quantified. Based on the image plane's normal, the rotational angular velocity of the radar LOS was estimated. The cross-range direction of the ISAR image was then calibrated. Three-dimensional imaging was then reconstructed based on dual station interferometry. Finally, simulations were performed to verify the result of the three-dimensional interferometric reconstruction and to calculate the reconstruction's precision errors.

  19. A Parametric Study on Using Active Debris Removal for LEO Environment Remediation

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Recent analyses on the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited the interest in using active debris removal (ADR) to remediate the environment. There are; however, monumental technical, resource, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of its effectiveness must be conducted. The goal is to demonstrate the need and feasibility of using ADR to better preserve the future environment and to guide its implementation to maximize the benefit-to-cost ratio. This paper describes a new sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term orbital debris evolutionary model, LEGEND, is used to quantify the effects of several key parameters, including target selection criteria/constraints and the starting epoch of ADR implementation. Additional analyses on potential ADR targets among the currently existing satellites and the benefits of collision avoidance maneuvers are also included.

  20. Preliminary Study of Geosynchronous Orbit Transfers from LEO using Invariant Manifolds

    NASA Astrophysics Data System (ADS)

    Davis, Kathryn E.; Anderson, Rodney L.; Born, George H.

    2011-07-01

    The invariant manifolds of libration point orbits (LPOs) in the Sun-Earth/Moon system are used to construct low-energy transfers from Low Earth Orbits (LEOs) to geosynchronous orbits. A maneuver is performed in LEO to insert onto a stable manifold trajectory of an LPO. The spacecraft travels to the host LPO and then follows an unstable manifold trajectory back to a geosynchronous orbit, where an orbit insertion maneuver is performed. The gravitational effects of the Sun-Earth/Moon three-body system act in such a way that large plane changes between the initial and final orbits at Earth may be realized without the execution of any plane change maneuvers. The maneuver costs of the transfers that employ invariant manifolds are compared to those using traditional techniques. The transfers that employ manifold trajectories can lower the cost of traditional Hohmann transfers by up to 3.15 km/s for transfers involving large differences in initial and final inclinations. The decrease in fuel expenditure is accompanied by an increase in time of flight; transfer durations are slightly over one year.

  1. Development of HiLo Microscope and its use in In-Vivo Applications

    NASA Astrophysics Data System (ADS)

    Patel, Shreyas J.

    The functionality of achieving optical sectioning in biomedical research is invaluable as it allows for visualization of a biological sample at different depths while being free of background scattering. Most current microscopy techniques that offer optical sectioning, unfortunately, require complex instrumentation and thus are generally costly. HiLo microscopy, on the other hand, offers the same functionality and advantage at a relatively low cost. Hence, the work described in this thesis involves the design, build, and application of a HiLo microscope. More specifically, a standalone HiLo microscope was built in addition to implementing HiLo microscopy on a standard fluorescence microscope. In HiLo microscopy, optical sectioning is achieved by acquiring two different types of images per focal plane. One image is acquired under uniform illumination and the other is acquired under speckle illumination. These images are processed using an algorithm that extracts in-focus information and removes features and glare that occur as a result of background fluorescence. To show the benefits of the HiLo microscopy, several imaging experiments on various samples were performed under a HiLo microscope and compared against a traditional fluorescence microscope and a confocal microscope, which is considered the gold standard in optical imaging. In-vitro and ex-vivo imaging was performed on a set of pollen grains, and optically cleared mouse brain and heart slices. Each of these experiments showed great reduction in background scattering at different depths under HiLo microscopy. More importantly, HiLo imaging of optically cleared heart slice demonstrated emergence of different vasculature at different depths. Reduction of out-of-focus light increased the spatial resolution and allowed better visualization of capillary vessels. Furthermore, HiLo imaging was tested in an in-vivo model of a rodent dorsal window chamber model. When imaging the same sample under confocal microscope

  2. Effect of Propellant Flowrate and Purity on Carbon Deposition in LO2/Methane Gas Generators

    NASA Technical Reports Server (NTRS)

    Bossard, J. A.; Burkhardt, W. M.; Niiya, K. Y.; Braam, F.

    1989-01-01

    The generation and deposition of carbon was studied in the Carbon Deposition Program using subscale hardware with LO2/Liquid Natural Gas (LNG) and LO2/Methane propellants at low mixture ratios. The purpose of the testing was to evaluate the effect of methane purity and full scale injection density on carbon deposition. The LO2/LNG gas generator/preburner testing was performed at mixture ratios between 0.24 and 0.58 and chamber pressures from 5.8 to 9.4 MPa (840 to 1370 psia). A total of seven 200 second duration tests were performed. The LNG testing occurred at low injection densities, similar to the previous LO2/RP-1, LO2/propane, and LO2/methane testing performed on the carbon deposition program. The current LO2/methane test series occurred at an injection density factor of approximately 10 times higher than the previous testing. The high injection density LO2/methane testing was performed at mixture ratios between from 0.23 to 0.81 and chamber pressures from 6.4 to 15.2 MPa (925 to 2210 psia). A total of nine high injection density tests were performed. The testing performed demonstrated that low purity methane (LNG) did not produce any detectable change in carbon deposition when compared to pure methane. In addition, the C* performance and the combustion gas temperatures measured were similar to those obtained for pure methane. Similar results were obtained testing pure methane at higher propellant injection densities with coarse injector elements.

  3. m-LoCoS UI: A Universal Visible Language for Global Mobile Communication

    NASA Astrophysics Data System (ADS)

    Marcus, Aaron

    The LoCoS universal visible language developed by the graphic/sign designer Yukio Ota in Japan in 1964 may serve as a usable, useful, and appealing basis for a mobile phone application that can provide capabilities for communication and storytelling among people who do not share a spoken language. User-interface design issues including display and input are discussed in conjunction with prototype screens showing the use of LoCoS for a mobile phone.

  4. Measurement Properties of the Low Back Activity Confidence Scale (LoBACS).

    PubMed

    Davenport, Todd E; Cleland, Joshua A; Yamada, Kimiko A; Kulig, Kornelia

    2016-06-01

    The purpose of this study was to determine the measurement properties of the Low Back Activity Confidence Scale (LoBACS) in individuals with post-acute low back pain (LBP) receiving nonsurgical intervention, including construct validity, factorial validity, and internal consistency reliability. Data were analyzed from an existing randomized clinical trial involving 112 patients with LBP. Evidence for convergent validity was observed through significant correlations between LoBACS subscale scores and other function, pain, and psychobehavioral measures. LoBACS subscales accounted for 36% of the unique variance in dependent variable measurements, suggesting a satisfactory level of statistical divergence between the LoBACS and other psychobehavioral measurements in this study. Cronbach's α ranged from .88 to .92 for LoBACS subscales, and item-total correlations exceeded .6, indicating high internal consistency reliability. Principal axis factoring confirmed the hypothesized three-subscale structure by correctly classifying 14 of the 15 items. These findings indicate the LoBACS is valid and internally consistent to measure domain-specific self-efficacy beliefs. PMID:24686745

  5. Frontiers in Laser Cooling, Single-Molecule Biophysics, and Enrgy Science: A Talk from Leo Holberg and Allen Mills

    ScienceCinema

    Holberg, Leo; Mills, Allen [NIST

    2016-07-12

    Leo Holberg and Allen Mills present a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.

  6. LCT for EDRS: LEO to GEO optical communications at 1,8 Gbps between Alphasat and Sentinel 1a

    NASA Astrophysics Data System (ADS)

    Zech, H.; Heine, F.; Tröndle, D.; Seel, S.; Motzigemba, M.; Meyer, R.; Philipp-May, S.

    2015-10-01

    The European Data Relay System (EDRS) relies on optical communication links between Low Earth Orbit (LEO) and geostationary (GEO) spacecrafts. Data transmission at 1,8 Gbps between the S/Cs will be applied for link distances up to 45000 km. EDRS is foreseen to go into operation in 2015. As a precursor to the EDRS GEO Laser Communication Terminals (LCT), a LCT is embarked on the Alphasat GEO S/C, which was launched in July 2013. Sentinel 1A is a LEO earth observation satellite as part of ESAs Copernicus program. Sentinel 1A also has a LCT on board. In November 2014, the first optical communication link between a LEO and a GEO Laser Communication Terminal at gigabit data rates has been performed successfully [1]. Data generated by the Sentinel 1A instrument were optically transferred to Alphasat. From Alphasat, the data were transmitted via Kaband to a ground station. In the ground station, the original data were recovered successfully. So the whole chain from LEO to ground was verified. Since then, many optical communication links between the Alphasat LCT and the Sentinel 1A LCT were performed. During these tests, the acquisition and tracking performance was investigated. The first communication links showed a very robust link acquisition capability and tracking errors in the sub-μrad range. The communication link budget was verified and compared to the predictions, showing excellent overall system behavior with sufficient margin to support future GEO GEO link applications.

  7. A Vibrant & Vital Language Is Passed Down to a New Generation: The Punana Leo Immersion Schools in Hawai'i.

    ERIC Educational Resources Information Center

    Sorensen, Barbara

    1998-01-01

    Describes the Punana Leo Immersion Schools in Hawai'i, founded in 1983 by a group of Hawai'ian-language educators concerned about the impending extinction of their language. A second part describes two of the teachers and their philosophy about imparting language skill through spirit and culture. Sidebar describes the Advocates for Indigenous…

  8. From Leo Strauss to Collapse Theory: Considering the Neoconservative Attack on Modernity and the Work of Education

    ERIC Educational Resources Information Center

    Smith, David Geoffrey

    2008-01-01

    This paper locates the work of Leo Strauss within the broader conservative assault on modernity and especially its roots in liberalism. Four themes from Strauss's work are identified, then hermeneutically engaged for their relevance to educational practice in global times. The four themes are: (1) the liberal/modern concept of an open society is…

  9. Modeling of LEO Orbital Debris Populations in Centimeter and Millimeter Size Regimes

    NASA Technical Reports Server (NTRS)

    Xu, Y.-L.; Hill, . M.; Horstman, M.; Krisko, P. H.; Liou, J.-C.; Matney, M.; Stansbery, E. G.

    2010-01-01

    The building of the NASA Orbital Debris Engineering Model, whether ORDEM2000 or its recently updated version ORDEM2010, uses as its foundation a number of model debris populations, each truncated at a minimum object-size ranging from 10 micron to 1 m. This paper discusses the development of the ORDEM2010 model debris populations in LEO (low Earth orbit), focusing on centimeter (smaller than 10 cm) and millimeter size regimes. Primary data sets used in the statistical derivation of the cm- and mm-size model populations are from the Haystack radar operated in a staring mode. Unlike cataloged objects of sizes greater than approximately 10 cm, ground-based radars monitor smaller-size debris only in a statistical manner instead of tracking every piece. The mono-static Haystack radar can detect debris as small as approximately 5 mm at moderate LEO altitudes. Estimation of millimeter debris populations (for objects smaller than approximately 6 mm) rests largely on Goldstone radar measurements. The bi-static Goldstone radar can detect 2- to 3-mm objects. The modeling of the cm- and mm-debris populations follows the general approach to developing other ORDEM2010-required model populations for various components and types of debris. It relies on appropriate reference populations to provide necessary prior information on the orbital structures and other important characteristics of the debris objects. NASA's LEO-to-GEO Environment Debris (LEGEND) model is capable of furnishing such reference populations in the desired size range. A Bayesian statistical inference process, commonly adopted in ORDEM2010 model-population derivations, changes a priori distribution into a posteriori distribution and thus refines the reference populations in terms of data. This paper describes key elements and major steps in the statistical derivations of the cm- and mm-size debris populations and presents results. Due to lack of data for near 1-mm sizes, the model populations of 1- to 3.16-mm

  10. GPU-accelerated Faint Streak Detection for Uncued Surveillance of LEO

    NASA Astrophysics Data System (ADS)

    Zimmer, P.; Ackermann, M.; McGraw, J. T.

    2013-09-01

    By astronomical standards, small objects (<10cm) in LEO illuminated by the Sun under terminator conditions are quite bright, depositing 100's to 1000's of photons per second into small telescope apertures (< 1m diameter). The challenge in discovering these objects with no a priori knowledge of their orbit (i.e. uncued surveillance) is that their relative motion with respect to a ground-based telescope makes them appear to have large angular rates of motion, up to and exceeding 1 degree per second. Thus in even a short exposure, the signal from the object is smeared out in a streak with low signal-to-noise per pixel. Go Green Termite (GGT), Inc. of Gilroy, CA, in collaboration with the University of New Mexico (UNM), is building two proof-of-concept wide-field imaging systems to test, develop and prove a novel streak detection technique. The imaging systems are built from off-the-shelf optics and detectors resulting in a 350mm aperture and a 6 square degree field of view. For streak detection, field of view is of critical importance because the maximum exposure time on the object is limited by its crossing time. In this way, wider fields of view impact surveys for LEO objects both by increasing the survey volume and increasing sensitivity. Using our newly GPU-accelerated detection scheme, the proof-of-concept systems are expected to be able to detect objects fainter than 12th magnitude moving at 1 degree per second and possibly as faint as 13th magnitude for slower moving objects. Meter-class optical systems using these techniques should be able to detect objects fainter than 14th magnitude, which is roughly equivalent to a golf ball at 1000km altitude. The goal of this work is to demonstrate a scalable system for near real time detection of fast moving objects that can be then handed off to other instruments capable of tracking and characterizing them. The two proof-of-concept systems, separated by ~30km, work together by taking simultaneous images of the same

  11. Time variable gravity retrieval and treatment of temporal aliasing using optical two-way links between GALILEO and LEO satellites

    NASA Astrophysics Data System (ADS)

    Hauk, Markus; Pail, Roland; Murböck, Michael; Schlicht, Anja

    2016-04-01

    For the determination of temporal gravity fields satellite missions such as GRACE (Gravity Recovery and Climate Experiment) or CHAMP (Challenging Minisatellite Payload) were used in the last decade. These missions improved the knowledge of atmospheric, oceanic and tidal mass variations. The most limiting factor of temporal gravity retrieval quality is temporal aliasing due to the undersampling of high frequency signals, especially in the atmosphere and oceans. This kind of error causes the typical stripes in spatial representations of global gravity fields such as from GRACE. As part of the GETRIS (Geodesy and Time Reference in Space) mission, that aims to establish a geodetic reference station and precise time- and frequency reference in space by using optical two-way communication links between geostationary (GEO) and low Earth orbiting (LEO) satellites, a possible future gravity field mission can be set up. By expanding the GETRIS space segment to the global satellite navigation systems (GNSS) the optical two-way links also connect the GALILEO satellites among themselves and to LEO satellites. From these links between GALILEO and LEO satellites gravitational information can be extracted. In our simulations inter-satellite links between GALILEO and LEO satellites are used to determine temporal changes in the Earth's gravitational field. One of the main goals of this work is to find a suitable constellation together with the best analysis method to reduce temporal aliasing errors. Concerning non-tidal aliasing, it could be shown that the co-estimation of short-period long-wavelength gravity field signals, the so-called Wiese approach, is a powerful method for aliasing reduction (Wiese et al. 2013). By means of a closed loop mission simulator using inter-satellite observations as acceleration differences along the line-of-sight, different mission scenarios for GALILEO-LEO inter-satellite links and different functional models like the Wiese approach are analysed.

  12. ALFALFA DISCOVERY OF THE NEARBY GAS-RICH DWARF GALAXY LEO P. III. AN EXTREMELY METAL DEFICIENT GALAXY

    SciTech Connect

    Skillman, Evan D.; Berg, Danielle A.; Olive, Keith A.; McQuinn, Kristen B. W. E-mail: berg@astro.umn.edu E-mail: kmcquinn@astro.umn.edu; and others

    2013-07-01

    We present KPNO 4 m and LBT/MODS spectroscopic observations of an H II region in the nearby dwarf irregular galaxy Leo P discovered recently in the Arecibo ALFALFA survey. In both observations, we are able to accurately measure the temperature sensitive [O III] {lambda}4363 line and determine a ''direct'' oxygen abundance of 12 + log(O/H) = 7.17 {+-} 0.04. Thus, Leo P is an extremely metal deficient (XMD) galaxy, and, indeed, one of the most metal deficient star-forming galaxies ever observed. For its estimated luminosity, Leo P is consistent with the relationship between luminosity and oxygen abundance seen in nearby dwarf galaxies. Leo P shows normal {alpha} element abundance ratios (Ne/O, S/O, and Ar/O) when compared to other XMD galaxies, but elevated N/O, consistent with the ''delayed release'' hypothesis for N/O abundances. We derive a helium mass fraction of 0.2509{sup +0.0184}{sub -0.0123}, which compares well with the WMAP + BBN prediction of 0.2483 {+-} 0.0002 for the primordial helium abundance. We suggest that surveys of very low mass galaxies compete well with emission line galaxy surveys for finding XMD galaxies. It is possible that XMD galaxies may be divided into two classes: the relatively rare XMD emission line galaxies which are associated with starbursts triggered by infall of low-metallicity gas and the more common, relatively quiescent XMD galaxies like Leo P, with very low chemical abundances due to their intrinsically small masses.

  13. ALFALFA and WSRT Imaging of Extended H I Features in the Leo Cloud of Galaxies

    NASA Astrophysics Data System (ADS)

    Leisman, Lukas; Haynes, Martha P.; Giovanelli, Riccardo; Józsa, Gyula; Adams, Elizabeth A. K.; Hess, Kelley M.

    2016-08-01

    We present ALFALFA H I observations of a well studied region of the Leo Cloud, which includes the NGC 3227 group and the NGC 3190 group. We detect optically dark H I tails and plumes with extents potentially exceeding 600 kpc, well beyond the field of view of previous observations. These H I features contain ˜40% of the total H I mass in the NGC 3227 group and ˜10% of the NGC 3190 group. We also present WSRT maps which show the complex morphology of the the extended emission in the NGC 3227 group. We comment on previously proposed models of the interactions in these group and the implications for the scale of group processing through interactions. Motivated by the extent of the H I plumes, we place the H I observations in the context of the larger loose group, demonstrating the need for future sensitive, wide field H I surveys to understand the role of group processing in galaxy evolution.

  14. The critical density theory in LEO as analyzed by EVOLVE 4.0

    NASA Astrophysics Data System (ADS)

    Krisko, Paula H.; Opiela, John N.; Kessler, Donald J.

    2001-10-01

    The critical density theory is revisited with NASA's long-term debris environment model, EVOLVE 4.0. Previous studies were based on incomplete data and simplifying assumptions. Recent data of ground-test and on-orbit breakups and fragment decay have been utilized within the EVOLVE 4.0 structure to realistically model the projected low Earth orbit (LEO) debris environment. The EVOLVE 4.0 predictions over a 1000-year time period are shown to be consistent with the earlier predictions of simpler models; however, EVOLVE 4.0 is shown to be able to eliminate the simplifying assumptions in these earlier models and be a more accurate tool in understanding the most effective migration measures to limit future population growth.

  15. ALFALFA DISCOVERY OF THE NEARBY GAS-RICH DWARF GALAXY LEO P. II. OPTICAL IMAGING OBSERVATIONS

    SciTech Connect

    Rhode, Katherine L.; Salzer, John J.; Haurberg, Nathalie C.; Van Sistine, Angela; Young, Michael D.; Haynes, Martha P.; Giovanelli, Riccardo; Adams, Elizabeth A. K.; Cannon, John M.; Skillman, Evan D.; McQuinn, Kristen B. W. E-mail: slaz@astro.indiana.edu E-mail: haynes@astro.cornell.edu E-mail: jcannon@macalester.edu E-mail: kmcquinn@astro.umn.edu

    2013-06-15

    We present results from ground-based optical imaging of a low-mass dwarf galaxy discovered by the ALFALFA 21 cm H I survey. Broadband (BVR) data obtained with the WIYN 3.5 m telescope at Kitt Peak National Observatory (KPNO) are used to construct color-magnitude diagrams of the galaxy's stellar population down to V{sub o} {approx} 25. We also use narrowband H{alpha} imaging from the KPNO 2.1 m telescope to identify a H II region in the galaxy. We use these data to constrain the distance to the galaxy to be between 1.5 and 2.0 Mpc. This places Leo P within the Local Volume but beyond the Local Group. Its properties are extreme: it is the lowest-mass system known that contains significant amounts of gas and is currently forming stars.

  16. Planetary nebulae as standard candles. IV - A test in the Leo I group

    NASA Technical Reports Server (NTRS)

    Ciardullo, Robin; Jacoby, George H.; Ford, Holland C.

    1989-01-01

    In this paper, PN are used to determine accurate distances to three galaxies in the Leo I group - The E0 giant elliptical NGC 3379, its optical companion, the SB0 spiral NGC 3384, and the smaller E6 elliptical NGC 3377. In all three galaxies, the luminosity-specific PN number densities are roughly the same, and the derived stellar death rates are in remarkable agreement with the predictions of stellar evolution theory. It is shown that the shape of the forbidden O III 5007 A PN luminosity function is the same in each galaxy and indistinguishable from that observed in M31 and M81. It is concluded that the PN luminosity function is an excellent standard candle for early-type galaxies.

  17. The first case report of Leishmania (leishmania) chagasi in Panthera leo in Brazil.

    PubMed

    Dahroug, Magyda A A; Almeida, Arleana B P F; Sousa, Valéria R F; Dutra, Valéria; Guimarães, Luciana D; Soares, César E; Nakazato, Luciano; de Souza, Roberto L

    2011-06-01

    We reported here the first known case of natural infection of a lion (Panthera leo-Linnaeus, 1758) with Leishmania (Leishmania) chagasi (L. chagasi) in Brazil. The specimen was created by a circus handler in the state of Mato Grosso and was donated to the zoological park of the Federal University of Mato Grosso. Infection by L. chagasi was detected using a PCR-RFLP test. It was known that the domestic felids can act as reservoir of infection of L. chagasi in endemic areas, making it important that studies demonstrate their participation in the epidemiological chain. We demonstrate in this work that wild animals can have an important role in the epidemiological chain and must be considered in order to plan methods of control of this zoonosis.

  18. A Dynamic/Anisotropic Low Earth Orbit (LEO) Ionizing Radiation Model

    NASA Technical Reports Server (NTRS)

    Badavi, Francis F.; West, Katie J.; Nealy, John E.; Wilson, John W.; Abrahms, Briana L.; Luetke, Nathan J.

    2006-01-01

    The International Space Station (ISS) provides the proving ground for future long duration human activities in space. Ionizing radiation measurements in ISS form the ideal tool for the experimental validation of ionizing radiation environmental models, nuclear transport code algorithms, and nuclear reaction cross sections. Indeed, prior measurements on the Space Transportation System (STS; Shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the Low Earth Orbit (LEO) environment. Previous studies using Computer Aided Design (CAD) models of the evolving ISS configurations with Thermo Luminescent Detector (TLD) area monitors, demonstrated that computational dosimetry requires environmental models with accurate non-isotropic as well as dynamic behavior, detailed information on rack loading, and an accurate 6 degree of freedom (DOF) description of ISS trajectory and orientation.

  19. Hematologic and serum chemistry reference intervals for free-ranging lions (Panthera leo).

    PubMed

    Maas, Miriam; Keet, Dewald F; Nielen, Mirjam

    2013-08-01

    Hematologic and serum chemistry values are used by veterinarians and wildlife researchers to assess health status and to identify abnormally high or low levels of a particular blood parameter in a target species. For free-ranging lions (Panthera leo) information about these values is scarce. In this study 7 hematologic and 11 serum biochemistry values were evaluated from 485 lions from the Kruger National Park, South Africa. Significant differences between sexes and sub-adult (≤ 36 months) and adult (>36 months) lions were found for most of the blood parameters and separate reference intervals were made for those values. The obtained reference intervals include the means of the various blood parameter values measured in captive lions, except for alkaline phosphatase in the subadult group. These reference intervals can be utilized for free-ranging lions, and may likely also be used as reference intervals for captive lions.

  20. Analysis Of AVIRIS Data From LEO-15 Using Tafkaa Atmospheric Correction

    NASA Technical Reports Server (NTRS)

    Montes, Marcos J.; Gao, Bo-Cai; Davis, Curtiss O.; Moline, Mark

    2004-01-01

    We previously developed an algorithm named Tafkaa for atmospheric correction of remote sensing ocean color data from aircraft and satellite platforms. The algorithm allows quick atmospheric correction of hyperspectral data using lookup tables generated with a modified version of Ahmad & Fraser s vector radiative transfer code. During the past few years we have extended the capabilities of the code. Current modifications include the ability to account for within scene variation in solar geometry (important for very long scenes) and view geometries (important for wide fields of view). Additionally, versions of Tafkaa have been made for a variety of multi-spectral sensors, including SeaWiFS and MODIS. In this proceeding we present some initial results of atmospheric correction of AVIRIS data from the 2001 July Hyperspectral Coastal Ocean Dynamics Experiment (HyCODE) at LEO-15.

  1. Material interactions with the Low Earth Orbital (LEO) environment: Accurate reaction rate measurements

    NASA Technical Reports Server (NTRS)

    Visentine, James T.; Leger, Lubert J.

    1987-01-01

    To resolve uncertainties in estimated LEO atomic oxygen fluence and provide reaction product composition data for comparison to data obtained in ground-based simulation laboratories, a flight experiment has been proposed for the space shuttle which utilizes an ion-neutral mass spectrometer to obtain in-situ ambient density measurements and identify reaction products from modeled polymers exposed to the atomic oxygen environment. An overview of this experiment is presented and the methodology of calibrating the flight mass spectrometer in a neutral beam facility prior to its use on the space shuttle is established. The experiment, designated EOIM-3 (Evaluation of Oxygen Interactions with Materials, third series), will provide a reliable materials interaction data base for future spacecraft design and will furnish insight into the basic chemical mechanisms leading to atomic oxygen interactions with surfaces.

  2. NGSLR's Measurement of the Retro-Reflector Array Response of Various LEO to GNSS Satellites

    NASA Technical Reports Server (NTRS)

    McGarry, Jan; Clarke, Christopher; Degnan, John; Donovan, Howard; Hall, Benjamin; Hovarth, Julie; Zagwodzki, Thomas

    2012-01-01

    "NASA's Next Generation Satellite Laser Ranging System (NGSLR) has successfully demonstrated daylight and nighttime tracking this year to s atellites from LEO to GNSS orbits, using a 7-8 arcsecond beam divergence, a 43% QE Hamamatsu MCP-PMT with single photon detection, a narrow field of view (11 arcseconds), and a 1 mJ per pulse 2kHz repetition rate laser. We have compared the actual return rates we are getting against the theoretical link calculations, using the known system confi guration parameters, an estimate of the sky transmission using locall y measured visibility, and signal processing to extract the signal from the background noise. We can achieve good agreement between theory and measurement in most passes by using an estimated pOinting error. We will s.()w the results of this comparison along with our conclusio ns."

  3. Calling song signals and temporal preference functions in the cricket Teleogryllus leo.

    PubMed

    Rothbart, M M; Hennig, R M

    2012-11-01

    The acoustic display of many cricket species consists of trains of pulses (chirps) with intermittent pauses. Here, we investigated the temporal cues that females of the cricket Teleogryllus leo used to detect a pulse and a chirp pattern on two different time scales. For both patterns, females accepted a wide range of combinations that covered the respective pulse and chirp parameters in the songs of males. In tests with a continuous series of pulses at different modulation frequencies, the transfer function of pattern discrimination was also determined. Females exhibited two ranges of high response scores indicating two temporal filters with an inhibitory interaction. For the modulation frequency of the pulse pattern, the peak of the preference function was rather sharply tuned and at a lower pulse rate than produced by males. These results show that the combined output of both filters did not increase selectivity, but rather enlarged the accepted range of signals. PMID:22945775

  4. Changes in the structure and tribological property of Ag film by LEO space environment exposure

    NASA Astrophysics Data System (ADS)

    Gao, Xiaoming; Hu, Ming; Sun, Jiayi; Fu, Yanlong; Yang, Jun; Weng, Lijun; Liu, Weimin

    2014-11-01

    Ag films, deposited by arc ion plating, had been exposed for 43.5 h in real low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard the China Shenzhou-7 manned spaceship. The structure, morphology, composition and tribological property of the Ag films after the space environment exposure (SEE) were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. Depth XPS and XRD analysis revealed that after the SEE, the surface layer of Ag films was partially oxidized to Ag2O, the cracking and flaking phenomena could be observed from the film surface by FESEM, and so the Ag films lose its metallic shine and became gray. As a result, the tribological performance was deteriorated and the high/unstable friction was obtained.

  5. Age Estimation of African Lions Panthera leo by Ratio of Tooth Areas.

    PubMed

    White, Paula A; Ikanda, Dennis; Ferrante, Luigi; Chardonnet, Philippe; Mesochina, Pascal; Cameriere, Roberto

    2016-01-01

    Improved age estimation of African lions Panthera leo is needed to address a number of pressing conservation issues. Here we present a formula for estimating lion age to within six months of known age based on measuring the extent of pulp closure from X-rays, or Ratio Of tooth AReas (ROAR). Derived from measurements taken from lions aged 3-13 years for which exact ages were known, the formula explains 92% of the total variance. The method of calculating the pulp/tooth area ratio, which has been used extensively in forensic science, is novel in the study of lion aging. As a quantifiable measure, ROAR offers improved lion age estimates for population modeling and investigations of age-related mortality, and may assist national and international wildlife authorities in judging compliance with regulatory measures involving age.

  6. Age Estimation of African Lions Panthera leo by Ratio of Tooth Areas.

    PubMed

    White, Paula A; Ikanda, Dennis; Ferrante, Luigi; Chardonnet, Philippe; Mesochina, Pascal; Cameriere, Roberto

    2016-01-01

    Improved age estimation of African lions Panthera leo is needed to address a number of pressing conservation issues. Here we present a formula for estimating lion age to within six months of known age based on measuring the extent of pulp closure from X-rays, or Ratio Of tooth AReas (ROAR). Derived from measurements taken from lions aged 3-13 years for which exact ages were known, the formula explains 92% of the total variance. The method of calculating the pulp/tooth area ratio, which has been used extensively in forensic science, is novel in the study of lion aging. As a quantifiable measure, ROAR offers improved lion age estimates for population modeling and investigations of age-related mortality, and may assist national and international wildlife authorities in judging compliance with regulatory measures involving age. PMID:27089506

  7. The first case report of Leishmania (leishmania) chagasi in Panthera leo in Brazil

    PubMed Central

    Dahroug, Magyda AA; Almeida, Arleana BPF; Sousa, Valéria RF; Dutra, Valéria; Guimarães, Luciana D; Soares, César E; Nakazato, Luciano; de Souza, Roberto L

    2011-01-01

    We reported here the first known case of natural infection of a lion (Panthera leo-Linnaeus, 1758) with Leishmania (Leishmania) chagasi (L. chagasi) in Brazil. The specimen was created by a circus handler in the state of Mato Grosso and was donated to the zoological park of the Federal University of Mato Grosso. Infection by L. chagasi was detected using a PCR-RFLP test. It was known that the domestic felids can act as reservoir of infection of L. chagasi in endemic areas, making it important that studies demonstrate their participation in the epidemiological chain. We demonstrate in this work that wild animals can have an important role in the epidemiological chain and must be considered in order to plan methods of control of this zoonosis. PMID:23569768

  8. Age Estimation of African Lions Panthera leo by Ratio of Tooth Areas

    PubMed Central

    Ikanda, Dennis; Ferrante, Luigi; Chardonnet, Philippe; Mesochina, Pascal; Cameriere, Roberto

    2016-01-01

    Improved age estimation of African lions Panthera leo is needed to address a number of pressing conservation issues. Here we present a formula for estimating lion age to within six months of known age based on measuring the extent of pulp closure from X-rays, or Ratio Of tooth AReas (ROAR). Derived from measurements taken from lions aged 3–13 years for which exact ages were known, the formula explains 92% of the total variance. The method of calculating the pulp/tooth area ratio, which has been used extensively in forensic science, is novel in the study of lion aging. As a quantifiable measure, ROAR offers improved lion age estimates for population modeling and investigations of age-related mortality, and may assist national and international wildlife authorities in judging compliance with regulatory measures involving age. PMID:27089506

  9. A CRIRES-POP Atlas of the K Giant 10 Leo

    NASA Astrophysics Data System (ADS)

    Nicholls, C. P.; Lebzelter, T.

    2015-12-01

    The CRIRES-POP project (Lebzelter et al. [2]) will provide a public database of high-res, high S:N, NIR spectra of stars spanning the HR diagram. A relevant part of this library for the evolved star community will be the high quality reference spectra of several cool evolved giants. These atlases will be valuable references for future research, and will include comprehensive line identifications, abundance measurements, and isotope ratios, alongside stellar parameters derived through the inclusion of other data sources. All CRIRES observations have been completed, and reduction and analysis of the spectra, including improved telluric subtraction and wavelength calibration, is ongoing. We present here preliminary results of the first atlas to be produced, that of K1 III giant 10 Leo.

  10. Three Canted Radiator Panels to Provide Adequate Cooling for Instruments on Slewing Spacecraft in LEO

    NASA Technical Reports Server (NTRS)

    Choi, Michael K.

    2012-01-01

    Certain free-flying spacecraft in low Earth orbit (LEO) or payloads on the International Space Station (ISS) are required to slew to point the telescopes at targets. Instrument detectors and electronics require cooling. Traditionally a planar thermal radiator is used. The temperature of such a radiator varies significantly when the spacecraft slews because its view factors to space vary significantly. Also for payloads on the ISS, solar impingement on the radiator is possible. These thermal adversities could lead to inadequate cooling for the instrument. This paper presents a novel thermal design concept that utilizes three canted radiator panels to mitigate this problem. It increases the overall radiator view factor to cold space and reduces the overall solar or albedo flux absorbed per unit area of the radiator.

  11. The Structural Properties and Star Formation History of Leo T from Deep LBT Photometry

    NASA Astrophysics Data System (ADS)

    de Jong, J. T. A.; Harris, J.; Coleman, M. G.; Martin, N. F.; Bell, E. F.; Rix, H.-W.; Hill, J. M.; Skillman, E. D.; Sand, D. J.; Olszewski, E. W.; Zaritsky, D.; Thompson, D.; Giallongo, E.; Ragazzoni, R.; DiPaola, A.; Farinato, J.; Testa, V.; Bechtold, J.

    2008-06-01

    We present deep, wide-field g and r photometry of the transition-type dwarf galaxy Leo T, obtained with the blue arm of the Large Binocular Telescope. The data confirm the presence of both very young (<1 Gyr) and much older (>5 Gyr) stars. We study the structural properties of the old and young stellar populations by preferentially selecting either population on the basis of their color and magnitude. The young population is significantly more concentrated than the old population, with half-light radii of 104 +/- 8 and 148 +/- 16 pc, respectively, and their centers are slightly offset. Approximately 10% of the total stellar mass is estimated to be represented by the young stellar population. Comparison of the color-magnitude diagram (CMD) with theoretical isochrones, as well as numerical CMD fitting, suggests that star formation began over 10 Gyr ago and continued in recent times until at least a few hundred Myr ago. The CMD-fitting results are indicative of two distinct star formation bursts, with a quiescent period around 3 Gyr ago, albeit at low significance. The results are consistent with no metallicity evolution and a value of [ Fe/H ] ~ - 1.5 over the entire age of the system. Finally, the data show little, if any, sign of tidal distortion of Leo T. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. The LBT Corporation partners are the University of Arizona, on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; and The Research Corporation, on behalf of the University of Notre Dame, the University of Minnesota, and the University of Virginia.

  12. Cycle life testing of lithium-ion batteries for small satellite LEO space missions

    SciTech Connect

    Mayer, S.T.; Feikert, J.H.; Kaschmitter, J.L.

    1993-08-16

    In 1990, Sony corporation announced their intention to manufacture a rechargeable lithium ion battery, based on the intercalation of lithium ions into a carbonaceous anode. The cells were first introduced for portable telephone use in June, 1991. (1) A 3.6V average cell voltage (4.1-2.75V range); (2) Excellent cycle life (1200 @ 100% DOD); (3) Good capacity retention (70% after 6 months); (4) Wide temperature range performance ({minus}20 to +60{degrees}C); (5) Excellent Discharge rate (82% capacity at 30 min. discharge rate); (6) Excellent Charge rate (100% Charge in <3 hrs); and (7) High energy density (264 W*hr/1 and 120 Whr/kg for ``D`` size cell. These specifications show significant promise for application of these batteries in low earth orbit (LEO) small satellites, particularly when compared to existing NiH{sub 2} and NiCd technology. The very high energy density and specific energy will reduce power system volume and weight. The wide temperature range enables simpler thermal design, particularly for new, small, high power satellites. The materials used in the lithium ion batteries are relatively inexpensive and benign, so that we expect costs to come down substantially in the future. The specified cycle life at 100% DOD is also 50% longer than most NiCds, so low DOD (depth of discharge) performance could be substantial. This study was undertaken to: (a) assess the feasibility for using lithium ion cells on small satellite LEO missions and (b) verify the claims of the manufacturer. This was accomplished by performing a detailed autopsy and various depth of discharge and rate tests on the cells. Of special interest was the cycle life performance of these cell at various depths of discharge DOD`s, to get an initial measure of the reduction in capacity fade with cycle conditions. Low DOD`s are used to extend the life of all batteries used in a space application.

  13. CO2 sequestration through weathering of basalt tephra in the Landscape Evolution Observatory (LEO)

    NASA Astrophysics Data System (ADS)

    Van Haren, J. L.; Barron-Gafford, G.; Dontsova, K.

    2013-12-01

    Weathering of primary silicates is one of the mechanisms involved in carbon removal from the atmosphere, affecting the carbon cycle at geologic timescales. Basalt is one of the most reactive rocks and thus a strong contributor to geologic weathering fluxes. The Landscape Evolution Observatory (LEO), an Earth science research facility at Biosphere 2, Tucson, AZ, consisting of three identical 350m2 and 1m deep slopes, allows conducting controlled experiments investigating the interactions between atmosphere, hydrosphere, lithosphere, and biosphere at an unprecedented scale. This study presents results of the initial experiments where granular basalt that serves as a soil medium in LEO was exposed to rainfall. Soil solution and drainage were collected and analyzed to determine changes in solution composition. Gas-phase CO2 concentrations in the soil were monitored using custom gas samplers and Vaisala CO2 probes and CO2 gas fluxes on the surface was determined using soil chambers. The goal of the study was to determine the impact of precipitation on incipient CO2 driven weathering reactions and inorganic C sequestration in the basalt and how these reactions were distributed along hillslope flow paths. Results indicate a very strong relationship between water inputs and soil CO2 concentrations and fluxes. Within hours of a rainfall event, the surface CO2flux increased three-fold, while soil CO2 concentrations were reduced from near atmospheric to <100ppm (Figure 1). In addition, significant sequestration and leaching of inorganic carbon was observed, along with significant weathering of basalt and development of heterogeneity in solution-phase composition. Together, these results highlight the high rates of both chemical weathering, carbon sequestration, and soil formation in the early stages of landscape evolution. Figure 1. Soil CO2 concentrations as a function of the moisture content.

  14. Coronal Loops Heating in the Atmosphere of the Ad Leo Red Dwarf

    NASA Astrophysics Data System (ADS)

    Zaitsev, V. V.; Kronshtadtov, P. V.

    2016-08-01

    We study the possible origin of long-lasting soft X-ray flares on the AD Leo star, which were observed onboard the Extreme Ultraviolet Explorer (EUVE) spacecraft for the period of 1993-2000 [1]. These flares have relatively long rise and decay times of the radiation intensity ( τ R ≈ 104 s and τ d ≈ 5 · 103, respectively), as well as a relatively large emission measure EM ≈ 1051cm-3, which exceeds by 1-3 orders of magnitude the emission measure of soft X-ray flares on the Sun. Assuming that the radiation appears in magnetic loops and basing on the observed values of the emission measure and radiation decay time, the authors of [1] determined the typical length overline{l}≈ 1.5\\cdot {10}^{10} cm , electron number density overline{n}≈ 3\\cdot {10}^{11}c{m}^{-3} , and plasma temperature overline{T}≈ 2.5\\cdot 107 K of the loops. This paper considers plasma heating due to dissipation of the electric currents in the coronal magnetic loops of the star induced by the photospheric convection. The large inductance of the loop as an equivalent electric circuit determines the long time of the current rise in the source and explains the observed time of plasma heating and the rise time of the X-ray radiation intensity. It is shown that the parameters of the X-ray sources in the AD Leo atmosphere agree with the parameters calculated under the assumption of simultaneous emission of a great number of loops (about 50) with electric currents greater than 1013 A, which exceeds the electric currents in the solar coronal magnetic loops by 1-3 orders of magnitude. Such an exceeding can be related to the higher photospheric convection velocities on the late-type stars compared with the Sun.

  15. A Sensitivity Study on the Effectiveness of Active Debris Removal in LEO

    NASA Technical Reports Server (NTRS)

    Liou, J. C.; Johnson, Nicholas L.

    2007-01-01

    The near-Earth orbital debris population will continue to increase in the future due to ongoing space activities, on-orbit explosions, and accidental collisions among resident space objects. Commonly adopted mitigation measures, such as limiting postmission orbital lifetimes of satellites to less than 25 years, will slow down the population growth, but may be insufficient to stabilize the environment. The nature of the growth, in the low Earth orbit (LEO) region, is further demonstrated by a recent study where no future space launches were conducted in the environment projection simulations. The results indicate that, even with no new launches, the LEO debris population would remain relatively constant for only the next 50 years. Beyond that, the debris population would begin to increase noticeably, due to the production of collisional debris. Therefore, to better limit the growth of future debris population to protect the environment, remediation option, i.e., removing existing large and massive objects from orbit, needs to be considered. This paper does not intend to address the technical or economical issues for active debris removal. Rather, the objective is to provide a sensitivity study to quantify the effectiveness of various remediation options. A removal criterion based upon mass and collision probability is developed to rank objects at the beginning of each projection year. This study includes simulations with removal rates ranging from 2 to 20 objects per year, starting in the year 2020. The outcome of each simulation is analyzed, and compared with others. The summary of the study serves as a general guideline for future debris removal consideration.

  16. A new concept for high-cycle-life LEO: Rechargeable MnO2-hydrogen

    NASA Technical Reports Server (NTRS)

    Appleby, A. John; Dhar, Y. J.; Murphy, O. J.; Srinivasan, Supramaniam

    1989-01-01

    The nickel-hydrogen secondary battery system is now the one of choice for use in GEO satellites. It offers superior energy density to that of nickel-cadmium, with a lifetime that is at least comparable in terms of both cycle life and overall operating life. While the number of deep cycles required for GEO use is small, LEO satellites with long lifetimes (5 to 10 years) will require secondary battery systems allowing 30,000 to 60,000 useful cycles which are characterized by an approximately 2C charge rate and C average discharge rate. Recent work has shown that birnessite MnO2 doped with bismuth oxide can be cycled at very high rates (6C) over a very large number of cycles (thousands) at depths-of-discharge in the 85 to 90 percent range, based on two electrons, which discharge at the same potential in a flat plateau. The potential is about 0.7 V vs. hydrogen, with a cut-off at 0.6 V. At first sight, this low voltage would seem to be a disadvantage, since the theoretical energy density will be low. However, it permits the use of lightweight materials that are immune from corrosion at the positive. The high utilization and low equivalent weight of the active material, together with the use of teflon-bonded graphite for current collection, result in very light positives, especially when these are compared with those in a derated nickel-hydrogen system. In addition, the weight of the pressure vessel falls somewhat, since the dead volume is lower. Calculations show that a total system will have 2.5 times the Ah capacity of a derated nickel-hydrogen LEO battery, so that the energy density, based on 1.2 V for nickel-hydrogen and 0.7 V for MnO2-hydrogen, will be 45 percent higher for comparable cycling performance.

  17. HST images of FeLoBAL quasars: Testing quasar-galaxy evolution models

    NASA Astrophysics Data System (ADS)

    Herbst, Hanna; Hamann, Fred; Villforth, Carolin; Caselli, Paola; Koekemoer, Anton M.; Veilleux, Sylvain

    2016-01-01

    We present preliminary results from an HST imaging study of FeLoBAL quasars, which have extremely low-ionization Broad Absorption Line (BAL) outflows and might be a young quasar population based on their red colors, large far-IR luminosities (suggesting high star formation rates), and powerful outflows. Some models of quasar - host galaxy evolution propose a triggering event, such as a merger, to fuel both a burst of star formation and the quasar/AGN activity. These models suggest young quasars are initially obscured inside the dusty starburst until a "blowout" phase, driven by the starburst or quasar outflows like FeLoBALs, ends the star formation and reveals the visibly luminous quasar. Despite the popularity of this evolution scheme, there is little observational evidence to support the role of mergers in triggering AGN or the youth of dust-reddened quasars (such as FeLoBALs) compared to normal blue quasars.Our Cycle 22 HST program is designed to test the youth of FeLoBAL quasars and the connection of FeLoBALs to mergers. We obtain WFC3/IR F160W images of 10 FeLoBAL quasars at redshift z~0.9 (covering ~8500A in the quasar rest frame). We will compare the host galaxy morphologies and merger signatures of FeLoBALs with normal blue quasars (which are older according to the evolution model) and non-AGN galaxies matched in redshift and stellar mass. If FeLoBAL quasars are indeed in a young evolutionary state, close in time to the initial merging event, they should have stronger merger features compared to blue quasars and non-AGN galaxies. Preliminary results suggest that this is not the case - FeLoBAL quasars appear to reside in faint, compact hosts with weak or absent merger signatures. We discuss the implications of these results for galaxy evolution models and other studies of dust-reddened quasar populations.

  18. Optically sectioned in vivo imaging with speckle illumination HiLo microscopy.

    PubMed

    Lim, Daryl; Ford, Tim N; Chu, Kengyeh K; Mertz, Jerome

    2011-01-01

    We present a simple wide-field imaging technique, called HiLo microscopy, that is capable of producing optically sectioned images in real time, comparable in quality to confocal laser scanning microscopy. The technique is based on the fusion of two raw images, one acquired with speckle illumination and another with standard uniform illumination. The fusion can be numerically adjusted, using a single parameter, to produce optically sectioned images of varying thicknesses with the same raw data. Direct comparison between our HiLo microscope and a commercial confocal laser scanning microscope is made on the basis of sectioning strength and imaging performance. Specifically, we show that HiLo and confocal 3-D imaging of a GFP-labeled mouse brain hippocampus are comparable in quality. Moreover, HiLo microscopy is capable of faster, near video rate imaging over larger fields of view than attainable with standard confocal microscopes. The goal of this paper is to advertise the simplicity, robustness, and versatility of HiLo microscopy, which we highlight with in vivo imaging of common model organisms including planaria, C. elegans, and zebrafish. PMID:21280920

  19. Selenoprotein X Gene Knockdown Aggravated H2O2-Induced Apoptosis in Liver LO2 Cells.

    PubMed

    Tang, Jiayong; Cao, Lei; Li, Qiang; Wang, Longqiong; Jia, Gang; Liu, Guangmang; Chen, Xiaoling; Cai, Jingyi; Shang, Haiying; Zhao, Hua

    2016-09-01

    To determine the roles of selenoprotein X gene (Selx) in protecting liver cells against oxidative damage, the influences of Selx knockdown on H2O2-induced apoptosis in human normal hepatocyte (LO2) cells were studied. pSilencer 3.1 was used to develop knockdown vector targeting the 3'-UTR of human Selx. The Selx knockdown and control cells were further exposed to H2O2, and cell viability, cell apoptosis rate, and the expression levels of mRNA and protein of apoptosis-related genes were detected. The results showed that vector targeting the 3'-UTR of Selx successfully silenced mRNA or protein expression of SelX in LO2 cells. Selx knockdown resulted in decreased cell viability, increased percentage of early apoptotic cells, decreased Bcl2A1 and Bcl-2 expression, and increased phosphorylation of P38 in LO2 cells. When Selx knockdown LO2 cells were exposed to H2O2, characteristics of H2O2-induced cell dysfunctions were further exacerbated. Taken together, our findings suggested that SelX played important roles in protecting LO2 cells against oxidative damage and reducing H2O2-induced apoptosis in liver cells.

  20. Laminarin-induced apoptosis in human colon cancer LoVo cells.

    PubMed

    Ji, Chen-Feng; Ji, Yu-Bin

    2014-05-01

    A number of scientific studies have revealed that laminarin has antitumor effects. Therefore, the aim of the present study was to investigate the apoptosis of LoVo cells and the underlying mechanisms induced by laminarin. LoVo cells were treated with various concentrations of laminarin and fluorescence-inverted microscopy was used to observe the morphology of LoVo cells treated with laminarin. In addition, western blotting was performed to analyze the expression levels of death receptor (DR)4, DR5, TNF-related apoptosis-inducing ligand (TRAIL), Fas-associated protein with death domain (FADD), caspase-8, caspase-3, Bid and tBid. Flow cytometry was conducted to analyze the expressions of Bcl-2 and Bax, and spectrophotometry was performed to quantify the activity of caspases-8, -3, -6 and -7. Following the treatment of LoVo cells with laminarin for 24 h, the expression levels of DR4, DR5, TRAIL, FADD, Bid, tBid and Bax were observed to be upregulated, whereas the expression levels of pro-caspase-8, pro-caspase-3 and Bcl-2 were downregulated. In addition, the activities of casapse-8, -3, -6 and -7 were observed to increase, which was a significant difference when compared with those of the control group. Therefore, laminarin is considered to induce the apoptosis of LoVo cells, which may occur via a DR pathway, suggesting that laminarin may be a potent agent for cancer treatment.

  1. An Orientation Dependent Size Illusion Is Underpinned by Processing in the Extrastriate Visual Area, LO1

    PubMed Central

    Mikellidou, Kyriaki; Gouws, André D.; Clawson, Hannah; Thompson, Peter; Morland, Antony B.

    2016-01-01

    We use the simple, but prominent Helmholtz’s squares illusion in which a vertically striped square appears wider than a horizontally striped square of identical physical dimensions to determine whether functional magnetic resonance imaging (fMRI) BOLD responses in V1 underpin illusions of size. We report that these simple stimuli which differ in only one parameter, orientation, to which V1 neurons are highly selective elicited activity in V1 that followed their physical, not perceived size. To further probe the role of V1 in the illusion and investigate plausible extrastriate visual areas responsible for eliciting the Helmholtz squares illusion, we performed a follow-up transcranial magnetic stimulation (TMS) experiment in which we compared perceptual judgments about the aspect ratio of perceptually identical Helmholtz squares when no TMS was applied against selective stimulation of V1, LO1, or LO2. In agreement with fMRI results, we report that TMS of area V1 does not compromise the strength of the illusion. Only stimulation of area LO1, and not LO2, compromised significantly the strength of the illusion, consistent with previous research that LO1 plays a role in the processing of orientation information. These results demonstrate the involvement of a specific extrastriate area in an illusory percept of size. PMID:27733896

  2. Kinetic description of an electron--LO-phonon system with finite phonon lifetime

    SciTech Connect

    Nguyen, V.T.; Mahler, G. )

    1992-02-15

    We study the cooling of an electron plasma from a kinetic point of view. For this purpose, a quantum theory of fluctuations is applied to derive the kinetic equations for an electron--LO-phonon system from various model Hamiltonians. A polarization approximation is provided that goes beyond perturbation theory of the electron-phonon interaction. The description of electron-phonon energy exchange is shown to be impossible with the interacting Hamiltonian in Froehlich's one-phonon form unless dissipation of the bare LO phonon is included. For a Hamiltonian including effects of the scattering of LO phonons by acoustic phonons, kinetic equations are derived. The equation for LO phonons is shown to describe the collective excitations with finite lifetime, in the limiting case of weak damping of the plasmon-phonon coupled modes. A reduction of the cooling rate similar to the hot-phonon'' effect is shown to occur for the case of weak coupling without assuming a steady state of the LO phonons. Finally, an electron-phonon interaction Hamiltonian in two-phonon form is considered and it is shown that electron-phonon energy exchange may be described in the polarization approximation without introducing a finite phonon lifetime.

  3. Implementation and Evaluation of the Enhanced Header Compression (IPHC) for 6LoWPAN

    NASA Astrophysics Data System (ADS)

    Ludovici, Alessandro; Calveras, Anna; Catalan, Marisa; Gómez, Carles; Paradells, Josep

    6LoWPAN defines how to carry IPv6 packets over IEEE 802.15.4 low power wireless or sensor networks. Limited bandwidth, memory and energy resources require a careful application of IPv6 in a LoWPAN. The IEEE 802.15.4 standard defines a maximum frame size of 127 bytes that decreases to 102 bytes considering the header overhead. A further reduction is due to the security, network and transport protocols header overhead that, in case of IPv6 and UDP, leave only 33 bytes for application data. A compression algorithm is necessary in order to reduce the overhead and save space in data payload. This paper describes and compares the proposed IPv6 header compression mechanisms for 6LoWPAN environments.

  4. A Study of LoRa: Long Range & Low Power Networks for the Internet of Things.

    PubMed

    Augustin, Aloÿs; Yi, Jiazi; Clausen, Thomas; Townsley, William Mark

    2016-09-09

    LoRa is a long-range, low-power, low-bitrate, wireless telecommunications system, promoted as an infrastructure solution for the Internet of Things: end-devices use LoRa across a single wireless hop to communicate to gateway(s), connected to the Internet and which act as transparent bridges and relay messages between these end-devices and a central network server. This paper provides an overview of LoRa and an in-depth analysis of its functional components. The physical and data link layer performance is evaluated by field tests and simulations. Based on the analysis and evaluations, some possible solutions for performance enhancements are proposed.

  5. Improving high resolution retinal image quality using speckle illumination HiLo imaging

    PubMed Central

    Zhou, Xiaolin; Bedggood, Phillip; Metha, Andrew

    2014-01-01

    Retinal image quality from flood illumination adaptive optics (AO) ophthalmoscopes is adversely affected by out-of-focus light scatter due to the lack of confocality. This effect is more pronounced in small eyes, such as that of rodents, because the requisite high optical power confers a large dioptric thickness to the retina. A recently-developed structured illumination microscopy (SIM) technique called HiLo imaging has been shown to reduce the effect of out-of-focus light scatter in flood illumination microscopes and produce pseudo-confocal images with significantly improved image quality. In this work, we adopted the HiLo technique to a flood AO ophthalmoscope and performed AO imaging in both (physical) model and live rat eyes. The improvement in image quality from HiLo imaging is shown both qualitatively and quantitatively by using spatial spectral analysis. PMID:25136486

  6. A Study of LoRa: Long Range & Low Power Networks for the Internet of Things

    PubMed Central

    Augustin, Aloÿs; Yi, Jiazi; Clausen, Thomas; Townsley, William Mark

    2016-01-01

    LoRa is a long-range, low-power, low-bitrate, wireless telecommunications system, promoted as an infrastructure solution for the Internet of Things: end-devices use LoRa across a single wireless hop to communicate to gateway(s), connected to the Internet and which act as transparent bridges and relay messages between these end-devices and a central network server. This paper provides an overview of LoRa and an in-depth analysis of its functional components. The physical and data link layer performance is evaluated by field tests and simulations. Based on the analysis and evaluations, some possible solutions for performance enhancements are proposed. PMID:27618064

  7. A Study of LoRa: Long Range & Low Power Networks for the Internet of Things.

    PubMed

    Augustin, Aloÿs; Yi, Jiazi; Clausen, Thomas; Townsley, William Mark

    2016-01-01

    LoRa is a long-range, low-power, low-bitrate, wireless telecommunications system, promoted as an infrastructure solution for the Internet of Things: end-devices use LoRa across a single wireless hop to communicate to gateway(s), connected to the Internet and which act as transparent bridges and relay messages between these end-devices and a central network server. This paper provides an overview of LoRa and an in-depth analysis of its functional components. The physical and data link layer performance is evaluated by field tests and simulations. Based on the analysis and evaluations, some possible solutions for performance enhancements are proposed. PMID:27618064

  8. Refining the Technical Components for the Second Generation CMORPH: LEO-IR Based Precipitation Estimates and Cloud Motion Vector

    NASA Astrophysics Data System (ADS)

    Xie, P.; Joyce, R.; Wu, S.

    2015-12-01

    A prototype system was developed for the second generation CMORPH to produce global analyses of 30-min precipitation on a 0.05olat/lon grid over the entire globe from pole to pole through integration of information from satellite observations as well as numerical model simulations. The second generation CMORPH is built upon the Kalman Filter based CMORPH algorithm of Joyce and Xie (2011). Inputs to the system include rainfall and snowfall rate retrievals from passive microwave (PMW) measurements aboard all available low earth orbit (LEO) satellites, precipitation estimates derived from infrared (IR) observations of geostationary (GEO) as well as LEO platforms, and precipitation simulations from numerical global models. Key to the success of the 2nd generation CMORPH, among a couple of other elements, are the development of a LEO-IR based precipitation estimation to fill in the polar gaps and objectively analyzed cloud motion vectors to capture the cloud movements of various spatial scales over the entire globe. The prototype algorithm for the LEO IR precipitation estimation is refined to achieve improved quantitative accuracy and consistency with PMW retrievals. AVHRR IR TBB data from all LEO satellites are first remapped to a 0.05olat/lon grid over the entire globe and in a 30-min interval. AVHRR TBB - precipitation relationships are separately established through PDF calibration of the TBB data against temporally/spatially collocated combined PMW retrievals (MWCOMB) and against the CloudSat radar measurements, respectively, then combined using a weighted mean to reflect the strengths of both data sources. A sub-system is developed to construct analyzed fields of cloud motion vectors from the GEO/LEO IR based precipitation estimates and the CFS Reanalysis (CFSR) precipitation fields. Motion vectors are first derived separately from the satellite IR based precipitation estimates and the CFSR precipitation fields. These individually derived motion vectors are then

  9. Alfalfa discovery of the nearby gas-rich dwarf galaxy LEO P. V. Neutral gas dynamics and kinematics

    SciTech Connect

    Bernstein-Cooper, Elijah Z.; Pardy, Stephen A.; Cannon, John M. E-mail: spardy@astro.wisc.edu; and others

    2014-08-01

    We present new H I spectral line imaging of the extremely metal-poor, star-forming dwarf irregular galaxy Leo P. Our H I images probe the global neutral gas properties and the local conditions of the interstellar medium (ISM). The H I morphology is slightly elongated along the optical major axis. We do not find obvious signatures of interaction or infalling gas at large spatial scales. The neutral gas disk shows obvious rotation, although the velocity dispersion is comparable to the rotation velocity. The rotation amplitude is estimated to be V {sub c} =15 ± 5 km s{sup –1}. Within the H I radius probed by these observations, the mass ratio of gas to stars is roughly 2:1, while the ratio of the total mass to the baryonic mass is ≳15:1. We use this information to place Leo P on the baryonic Tully-Fisher relation, testing the baryonic content of cosmic structures in a sparsely populated portion of parameter space that has hitherto been occupied primarily by dwarf spheroidal galaxies. We detect the signature of two temperature components in the neutral ISM of Leo P; the cold and warm components have characteristic velocity widths of 4.2 ± 0.9 km s{sup –1} and 10.1 ± 1.2 km s{sup –1}, corresponding to kinetic temperature upper limits of ∼1100 K and ∼6200 K, respectively. The cold H I component is unresolved at a physical resolution of 200 pc. The highest H I surface densities are observed in close physical proximity to the single H II region. A comparison of the neutral gas properties of Leo P with other extremely metal-deficient (XMD) galaxies reveals that Leo P has the lowest neutral gas mass of any known XMD, and that the dynamical mass of Leo P is more than two orders of magnitude smaller than any known XMD with comparable metallicity.

  10. The Paf1 complex factors Leo1 and Paf1 promote local histone turnover to modulate chromatin states in fission yeast.

    PubMed

    Sadeghi, Laia; Prasad, Punit; Ekwall, Karl; Cohen, Amikam; Svensson, J Peter

    2015-12-01

    The maintenance of open and repressed chromatin states is crucial for the regulation of gene expression. To study the genes involved in maintaining chromatin states, we generated a random mutant library in Schizosaccharomyces pombe and monitored the silencing of reporter genes inserted into the euchromatic region adjacent to the heterochromatic mating type locus. We show that Leo1-Paf1 [a subcomplex of the RNA polymerase II-associated factor 1 complex (Paf1C)] is required to prevent the spreading of heterochromatin into euchromatin by mapping the heterochromatin mark H3K9me2 using high-resolution genomewide ChIP (ChIP-exo). Loss of Leo1-Paf1 increases heterochromatin stability at several facultative heterochromatin loci in an RNAi-independent manner. Instead, deletion of Leo1 decreases nucleosome turnover, leading to heterochromatin stabilization. Our data reveal that Leo1-Paf1 promotes chromatin state fluctuations by enhancing histone turnover.

  11. Estimating water vapour along the radio path between two LEO satellites through multifrequency differential power measurements

    NASA Astrophysics Data System (ADS)

    Facheris, Luca; Cuccoli, Fabrizio

    2013-04-01

    The Normalized Differential Spectral Attenuation (NDSA) concept was proposed in 2002 by the authors for tropospheric water vapour sounding by means of a couple of LEO (Low Earth Orbit) satellites (one carrying a transmitter, the other a receiver and operating in the Ku/K bands) in limb geometry. In those years, in the course of the ACE+ mission studies (second call for proposal of the ESA Earth Explorer Opportunity Mission), the problem arose of the severe impact of scintillation due to tropospheric turbulence on the water vapour estimates provided by radio occultation measurements made in limb mode between two LEO satellites. In following ESA studies (AlmetLeo - 2004, ACTLIMB -2009) it was demonstrated that NDSA, thanks to its normalised differential approach, is effective for limiting scintillation and for estimating the Integrated Water Vapor (IWV) along the propagation path between the two LEO satellites. NDSA relies on the conversion of a spectral parameter (the spectral sensitivity S), into the IWV through IWV-S relationships. S is a finite-difference approximation of the derivative of the spectral attenuation at a given frequency fo, normalized to the spectral attenuation itself. To measure Sat fo,it is required that two tone signals with equal power at relatively close frequencies f1 and f2 (f1 > f2) symmetrically placed around fo are simultaneously transmitted. The two pertinent received powers P1 and P2 are simultaneously measured and S is provided by: S = -P2--P1- (f1 - f2 )P2 From the very beginning of the NDSA studies, it was evident that in ideal measurement conditions (no disturbance at the receiver nor propagation impairments) S is tightly correlated to the IWV. To verify this, we accounted for natural variations of the atmospheric conditions by generating simulated spherically symmetric atmospheres using real radiosonde profiles. We computed IWV along the radio path and simulated S separately obtaining IWV-S relationships at various altitudes

  12. Comparison of currents predicted by NASCAP/LEO model simulations with elementary Langmuir-type bare probe models for an insulated cable containing a single pinhole

    NASA Technical Reports Server (NTRS)

    Galofaro, Joel T.

    1990-01-01

    The behavior of a defect in the insulation of a short biased section of cable in a Low Earth Orbit (LEO) space environment was examined. Such studies are of the utmost importance for large space power systems where great quantities of cabling will be deployed. An insulated probe containing a pinhole was placed into a hypothetical high speed LEO plasma. The NASA Charging Analyzer Program (NASCAP/LEO) was used to explore sheath growth about the probe as a function of applied voltage and to predict I-V behavior. A set of independent current calculations using Langmuir's formulations for concentric spheres and coaxial cylinders were also performed. The case of concentric spheres was here extended to include the case of concentric hemispheres. Several simple Langmuir-type models were then constructed to bracket the current collected by the cable. The space-charge sheath radius and impact parameters were used to determine the proper current regime. I-V curves were plotted for the models and comparisons were made with NASCAP/LEO results. Finally, NASCAP/LEO potential contours and surface cell potential plots were examined to explain interesting features in the NASCAP/LEO I-V curve.

  13. An Updated Zero Boil-Off Cryogenic Propellant Storage Analysis Applied to Upper Stages or Depots in a LEO Environment

    NASA Technical Reports Server (NTRS)

    Plachta, David; Kittel, Peter

    2003-01-01

    Previous efforts have shown the analytical benefits of zero boil-off (ZBO) cryogenic propellant storage in launch vehicle upper stages of Mars transfer vehicles for conceptual Mars Missions. However, recent NASA mission investigations have looked at a different and broad array of missions, including a variety of orbit transfer vehicle (OTV) propulsion concepts, some requiring cryogenic storage. For many of the missions, this vehicle will remain for long periods (greater than one week) in low earth orbit (LEO), a relatively warm thermal environment. Under this environment, and with an array of tank sizes and propellants, the performance of a ZBO cryogenic storage system is predicted and compared with a traditional, passive-only storage concept. The results show mass savings over traditional, passive-only cryogenic storage when mission durations are less than one week in LEO for oxygen, two weeks for methane, and roughly 2 months for LH2. Cryogenic xenon saves mass over passive storage almost immediately.

  14. Mapping the space radiation environment in LEO orbit by the SATRAM Timepix payload on board the Proba-V satellite

    NASA Astrophysics Data System (ADS)

    Granja, Carlos; Polansky, Stepan

    2016-07-01

    Detailed spatial- and time-correlated maps of the space radiation environment in Low Earth Orbit (LEO) are produced by the spacecraft payload SATRAM operating in open space on board the Proba-V satellite from the European Space Agency (ESA). Equipped with the hybrid semiconductor pixel detector Timepix, the compact radiation monitor payload provides the composition and spectral characterization of the mixed radiation field with quantum-counting and imaging dosimetry sensitivity, energetic charged particle tracking, directionality and energy loss response in wide dynamic range in terms of particle types, dose rates and particle fluxes. With a polar orbit (sun synchronous, 98° inclination) at the altitude of 820 km the payload samples the space radiation field at LEO covering basically the whole planet. First results of long-period data evaluation in the form of time-and spatially-correlated maps of total dose rate (all particles) are given.

  15. The Komplast Experiment: Space Environmental Effects after 12 Years in LEO (and Counting)

    NASA Technical Reports Server (NTRS)

    Shaevich, S. K.; Aleksandrov, N. G.; Shumov, A. E.; Novikov, L. S.; Alred, J. A.; Shindo, D. J.; Kravchenko, M.; Golden, J. L.

    2013-01-01

    The Komplast materials experiment was designed by the Khrunichev State Research and Production Space Center, together with other Russian scientific institutes, and has been carried out by Mission Control Moscow since 18. Komplast panels fitted with material samples and sensors were located on the International Space Station (ISS) Functional Cargo Block (FGB) module exterior surface. Within the framework of this experiment, the purpose was to study the effect of the low earth orbit (LEO) environment on exposed samples of various materials. The panels were sent into orbit with the FGB when it launched on November 20, 1998. Panels #2 and #10 were retrieved during Russian extravehicular activity in February 2011 and sealed within cases to temporarily protect the samples from exposure to air until they could be studied on the ground. Panel #2 contained an experiment to detect micrometeoroid and orbital debris (MMOD) impacts, radiation and UV sensors, several pieces of electrical cable, and samples made from elastomeric and fluoroplastic materials. Panel #10 contained a temperature sensor, and both carbon composite and adhesive-bonded samples. A figure shows the location of panels #2 and #10 on the FGB module aft endcone. The panels were subsequently returned to Earth by Space Shuttle Discovery on the STS-133/ULF-5 mission after 12 years of LEO exposure and opened in an argon chamber at the Institute of Nuclear Physics at Moscow State University in July 2011. Based on the results of analyzing the readings from sensors located on Komplast panels and in studying material samples from the panels, the comprehensive effect of spaceflight factors on the FGB (at the locations of Panels #2 and #10) was evaluated. Total solar exposure was determined to be 960 +/- 200 kJ/square cm or 21,000 equivalent solar hours. Because of location of these two panels and the ISS flight attitude, atomic oxygen (AO) fluence was relatively low for such a long duration exposure, approximately 1.5x

  16. Mission Analysis for LEO Microwave Power-Beaming Station in Orbital Launch of Microwave Lightcraft

    NASA Technical Reports Server (NTRS)

    Myrabo, L. N.; Dickenson, T.

    2005-01-01

    A detailed mission analysis study has been performed for a 1 km diameter, rechargeable satellite solar power station (SPS) designed to boost 20m diameter, 2400 kg Micr,oWave Lightcraft (MWLC) into low earth orbit (LEO) Positioned in a 476 km daily-repeating oi.bit, the 35 GHz microwave power station is configured like a spinning, thin-film bicycle wheel covered by 30% efficient sola cells on one side and billions of solid state microwave transmitter elements on the other, At the rim of this wheel are two superconducting magnets that can stor,e 2000 G.J of energy from the 320 MW, solar array over a period of several orbits. In preparation for launch, the entire station rotates to coarsely point at the Lightcraft, and then phases up using fine-pointing information sent from a beacon on-board the Lightcraft. Upon demand, the station transmits a 10 gigawatt microwave beam to lift the MWLC from the earth surface into LEO in a flight of several minutes duration. The mission analysis study was comprised of two parts: a) Power station assessment; and b) Analysis of MWLC dynamics during the ascent to orbit including the power-beaming relationships. The power station portion addressed eight critical issues: 1) Drag force vs. station orbital altitude; 2) Solar pressure force on the station; 3) Station orbital lifetime; 4) Feasibility of geo-magnetic re-boost; 5) Beta angle (i..e., sola1 alignment) and power station effective area relationship; 6) Power station percent time in sun vs, mission elapsed time; 7) Station beta angle vs.. charge time; 8) Stresses in station structures.. The launch dynamics portion examined four issues: 1) Ascent mission/trajecto1y profile; 2) MWLC/power-station mission geometry; 3) MWLC thrust angle vs. time; 4) Power station pitch rate during power beaming. Results indicate that approximately 0 58 N of drag force acts upon the station when rotated edge-on to project the minimum frontal area of 5000 sq m. An ion engine or perhaps an electrodynamic

  17. Homogeneous Photometry VI: Variable Stars in the Leo I Dwarf Spheroidal Galaxy

    NASA Astrophysics Data System (ADS)

    Stetson, Peter B.; Fiorentino, Giuliana; Bono, Giuseppe; Bernard, Edouard J.; Monelli, Matteo; Iannicola, Giacinto; Gallart, Carme; Ferraro, Ivan

    2014-07-01

    From archival ground-based images of the Leo I dwarf spheroidal galaxy, we have identified and characterized the pulsation properties of 164 candidate RR Lyrae variables and 55 candidate anomalous and/or short-period Cepheids. We have also identified 19 candidate long-period variable stars and 13 other candidate variables whose physical nature is unclear, but due to the limitations of our observational material we are unable to estimate reliable periods for them. On the basis of its RR Lyrae star population, Leo I is confirmed to be an Oosterhoff-intermediate type galaxy, like several other dwarf spheroidals. From the RR Lyrae stars we have derived a range of possible distance moduli for Leo I : 22.06 ± 0.08 lsim μ0 lsim 22.25 ± 0.07 mag depending on the metallicity assumed for the old population ([Fe/H] from -1.43 to -2.15). This is in agreement with previous independent estimates. We show that in their pulsation properties, the RR Lyrae stars—representing the oldest stellar population in the galaxy—are not significantly different from those of five other nearby, isolated dwarf spheroidal galaxies. A similar result is obtained when comparing them to RR Lyrae stars in recently discovered ultra-faint dwarf galaxies. We are able to compare the period distributions and period-amplitude relations for a statistically significant sample of ab-type RR Lyrae stars in dwarf galaxies (~1300 stars) with those in the Galactic halo field (~14,000 stars) and globular clusters (~1000 stars). Field RRLs show a significant change in their period distribution when moving from the inner (dG lsim 14 kpc) to the outer (dG gsim 14 kpc) halo regions. This suggests that the halo formed from (at least) two dissimilar progenitors or types of progenitor. Considered together, the RR Lyrae stars in classical dwarf spheroidal and ultra-faint dwarf galaxies—as observed today—do not appear to follow the well defined pulsation properties shown by those in either the inner or the outer

  18. Cutaneous squamous cell carcinoma presenting as a wound with discharging sinus tracts in a wild African lion (Panthera leo).

    PubMed

    Mwase, M; Mumba, C; Square, D; Kawarai, S; Madarame, H

    2013-11-01

    A female wild African lion (Panthera leo) was presented with an 8-month history of a wound with multiple discharging sinus tracts on the left paw. Microscopical examination revealed squamous cell carcinoma (SCC). To the best of our knowledge, this is the first report of cutaneous SCC in an African lion. Cutaneous SCC presenting as discharging sinus tracts lined by neoplastic squamous cells has not been reported previously in animals.

  19. Sizing of "Mother Ship and Catcher" Missions for LEO Small Debris and for GEO Large Object Capture

    NASA Technical Reports Server (NTRS)

    Bacon, John B.

    2009-01-01

    Most LEO debris lies in a limited number of inclination "bands" associated with specific useful orbits. Objects in such narrow inclination bands have all possible Right Ascensions of Ascending Node (RAANs), creating a different orbit plane for nearly every piece of debris. However, a low-orbiting satellite will always phase in RAAN faster than debris objects in higher orbits at the same inclination, potentially solving the problem. Such a low-orbiting base can serve as a "mother ship" that can tend and then send small, disposable common individual catcher/deboost devices--one for each debris object--as the facility drifts into the same RAAN as each higher object. The dV necessary to catch highly-eccentric orbit debris in the center of the band alternatively allows the capture of less-eccentric debris in a wider inclination range around the center. It is demonstrated that most LEO hazardous debris can be removed from orbit in three years, using a single LEO launch of one mother ship--with its onboard magazine of freeflying low-tech catchers--into each of ten identified bands, with second or potentially third launches into only the three highest-inclination bands. The nearly 1000 objects near the geostationary orbit present special challenges in mass, maneuverability, and ultimate disposal options, leading to a dramatically different architecture and technology suite than the LEO solution. It is shown that the entire population of near-GEO derelict objects can be gathered and tethered together within a 3 year period for future scrap-yard operations using achievable technologies and only two earth launches.

  20. Orbital period variations of four Algol-type eclipsing binaries: SW Cyg, UU Leo, XX Cep and BO Vul

    NASA Astrophysics Data System (ADS)

    Erdem, A.; Doğru, S. S.; Bakış, V.; Demircan, O.

    2007-07-01

    The orbital period behaviours of four Algol-type eclipsing binaries SW Cyg, UU Leo, XX Cep and BO Vul are studied, by using all available times of minimum light in the literature. Their O-C diagrams were represented by long-period sinusoidal variations superimposed on parabolic forms. The parabolic forms for SW Cyg and UU Leo correspond to secular period increases, while for XX Cep and BO Vul to secular period decreases. To explain these observed secular changes in these four Algol systems, we considered the combined effect of the mass transfer from the less massive component to the more massive one and the mass loss from the system. We concluded that the dominant mechanism for observed long-term period change of SW Cyg and UU Leo is the mass transfer, and that of XX Cep and BO Vul is the mass loss from the systems. It is interesting that the mass transfer rates (i.e., 10-7-10-8 M\\sun/yr) found for all four Algol binaries are at the upper limit of those generally accepted for Algols. However, assuming the mass loss via circumbinary disks of Chen et al. (2006) reduces the rate to 10-8-10-9 M\\sun/yr. We interpreted the tilted sinusoidal variations in all cases in terms of the light-time effect due to unseen components in the systems. Unacceptably large hypothetical third body masses in the case of SW Cyg and UU Leo, and common nature of the cyclic O-C variations in semi-detached Algols recall the cyclic magnetic activity effects of the secondary components as the working hypothesis in explaining cyclic period variations of these systems.

  1. Registration of WCL-LO4-Gail lesquerella with improved harvest index

    Technology Transfer Automated Retrieval System (TEKTRAN)

    WCL-LO4-Gail lesquerella (Physaria fendleri L.) germplasm line was publicly released jointly by the USDA, Agricultural Research Service and the University of Arizona, in 2012 as part of the new crops breeding program. The germplasm was developed by mass selection originating from lesquerella germpl...

  2. FLOYDS Classification of ASASSN-14lo as a Type Ia Supernova Near Peak

    NASA Astrophysics Data System (ADS)

    Arcavi, Iair; Sand, David; McCully, Curtis; Valenti, Stefano; Hosseinzadeh, Griffin; Howell, D. Andrew

    2014-12-01

    We obtained a spectrum of ASASSN-14lo (ATel #6794) on 2014 December 10 (UT) with the robotic FLOYDS instrument mounted on the Faulkes Telescope North. Using Superfit (Howell et al. 2005, ApJ 634, 1190) we find a good fit to the Type Ia SN 1996X around peak at the redshift of the proposed host galaxy (z=0.01993; NED).

  3. Numerical Investigation of LO2 and LCH4 Storage Tanks on the Lunar Surface

    NASA Technical Reports Server (NTRS)

    Moder, Jeff; Barsi, Stephen; Kassemi, Mohammad

    2008-01-01

    Currently NASA is developing technologies to enable human exploration of the lunar surface for duration of up to 210 days. While trade studies are still underway, a cryogenic ascent stage using liquid oxygen (LO2) and liquid methane (LCH4) is being considered for the Altair lunar lander. For a representative Altair cryogenic ascent stage, we present a detailed storage analysis of the LO2 and LCH4 propellant tanks on the lunar surface for durations of up to 210 days. Both the LO2 and LCH4 propellant tanks are assumed to be pressurized with gaseous helium at launch. A two-phase lumped-vapor computational fluid dynamics model has been developed to account for the presence of a noncondensable gas in the ullage. The CFD model is used to simulate the initial pressure response of the propellant tanks while they are subjected to representative heat leak rates on the lunar surface. Once a near stationary state is achieved within the liquid phase, multizone model is used to extrapolate the solution farther in time. For fixed propellant mass and tank size, the long-term pressure response for different helium mass fractions in both the LO2 and LCH4 tanks is examined.

  4. A Simultaneous Discovery: The Case of Johannes Stark and Antonino Lo Surdo

    NASA Astrophysics Data System (ADS)

    Leone, Matteo; Paoletti, Alessandro; Robotti, Nadia

    2004-09-01

    In 1913 the German physicist Johannes Stark (1874 1957) and the Italian physicist Antonino Lo Surdo (1880 1949)discovered virtually simultaneously and independently that hydrogen spectral lines are split into components by an external electric field. Both of their discoveries ensued from studies on the same phenomenon, the Doppler effect in canal rays, but they arose in different theoretical contexts. Stark had been working within the context of the emerging quantum theory, following a research program aimed at studying the effect of an electric field on spectral lines. Lo Surdo had been working within the context of the classical theory, and his was an accidental discovery. Both discoveries, however, played important roles in the history of physics: Stark’s discovery contributed to the establishment of both the old and the new quantum theories; Lo Surdo’s discovery led Antonio Garbasso (1871 1933)to introduce research on the quantum theory into Italian physics. Ironically, soon after their discoveries, both Stark and Lo Surdo rejected developments in modern physics and allied themselves with the political and racial programs of Hitler and Mussolini.

  5. Ka-im's Gift: A St:lo Legend (with Commentary by the Author).

    ERIC Educational Resources Information Center

    Gardner, Ethel B.

    1988-01-01

    Presents a modern retelling of a St:lo (Coast Salish) legend about the origin of a tribal treasure, the wondrous Sxwaixwe mask. Discusses the legend's origins, the process of transforming essentially oral sources into an accessible contemporary form, and the educational value of storytelling. Contains 13 references. (SV)

  6. Structural Validity of the Professional Development Profile of the LoTi Digital-Age Survey

    ERIC Educational Resources Information Center

    Mehta, Vandhana; Hull, Darrell M.

    2013-01-01

    The present study was used to examine the structural construct validity of the Professional Development Profile of the LoTi Digital-Age Survey, a measure of teacher instructional practices with technology in the classroom. Teacher responses ("N" = 2,840) from across the United States were used to assess factor structure of the instrument using…

  7. Coronal Dynamics and Complete Flare Energy Budget for the M Dwarf AD Leo

    NASA Technical Reports Server (NTRS)

    Brown, Alexander; Sonneborn, Georgwe (Technical Monitor)

    2005-01-01

    This grant supported the observing and data analysis for FUSE Cycle 3 project C114 to observe the flare star AD Leo for 50 ksec coordinated with HST (Hubble Space Telescope) STIS ultraviolet spectroscopy and Chandra X-ray spectroscopy. Unfortunately, it was impossible to obtain the planned FUSE observations because AD Leo is a low declination target (delta approximately 20 degrees) and was rendered unobservable by restrictions in the sky coverage for FUSE observations. In April 2002 another M dwarf star, EV Lac, which is at significantly higher declination, was substituted for this project. EV Lac was observed by FUSE for a cumulative exposure of 35 ksec on 2002 July 1. The observation used the large LWRS aperture and collected data in time-tagged mode. The LWRS aperture is large enough that the target should remain within the aperture despite the normal level of pointing jitter and target drift experienced during FUSE observing. Our examination of the stellar signal showed that the target was well within the aperture throughout the observation. The data were split into night-time and day-time data so that the effects of airglow emission were recognizable. No obvious flaring, the primary science objective, was detected during the observation. The only stellar lines detected are 0 VI 1031.9, 1037.6 Angstrom, and the C III 1175 Angstrom, UV multiplet and the 977 Angstrom, resonance line. A comparison of the day-time and night-time spectra show that the 0 VI lines and the C III intersystem multiplet are unaffected by airglow features. The day-time data 977 Angstrom profile shows the presence of significant scattered solar C III photons, which should not be present in the night time spectrum. Emission fluxes for these lines were measured by direct summation of the emission lines. No continuum signal was detected in the region of these lines. The cleanest emission line profiles are for the O VI lines and we performed Gaussian fitting for these profiles. Both lines are

  8. Short and long term efficiencies of debris risk reduction measures: Application to a European LEO mission

    NASA Astrophysics Data System (ADS)

    Lang, T.; Kervarc, R.; Bertrand, S.; Carle, P.; Donath, T.; Destefanis, R.; Grassi, L.; Tiboldo, F.; Schäfer, F.; Kempf, S.; Gelhaus, J.

    2015-01-01

    Recent numerical studies indicate that the low Earth orbit (LEO) debris environment has reached a point such that even if no further space launches were conducted, the Earth satellite population would remain relatively constant for only the next 50 years or so. Beyond that, the debris population would begin to increase noticeably, due to the production of collisional debris (Liou and Johnson, 2008). Measures to be enforced play thus a major role to preserve an acceptable space mission risk and ensure sustainable space activities. The identification of such measures and the quantification of their efficiency over time for LEO missions is of prime concern in the decision-making process, as it has been investigated for the last few decades by the Inter-Agency Space Debris Coordination Committee (IADC). This paper addresses the final results of a generic methodology and the characteristics of a tool developed to assess the efficiency of the risk reduction measures identified for the Sentinel-1 (S1) mission. This work is performed as part of the 34-month P2-ROTECT project (Prediction, Protection & Reduction of OrbiTal Exposure to Collision Threats), funded by the European Union within the Seventh Framework Programme. Three ways of risk reduction have been investigated, both in short and long-term, namely: better satellite protection, better conjunction prediction, and cleaner environment. According to our assumptions, the S1 mission vulnerability evaluations in the long term (from 2093 to 2100) show that full compliance to the mitigation measures leads to a situation twice safer than that induced by an active debris removal of 5 objects per year in a MASTER2009 Business-As-Usual context. Because these measures have visible risk reduction effects in the long term, complementary measures with short response time are also studied. In the short term (from 2013 to 2020), a better prediction of the conjunctions is more efficient than protecting the satellite S1 itself. By

  9. First Asian record of Panthera (Leo) fossilis (Mammalia, Carnivora, Felidae) in the Early Pleistocene of Western Siberia, Russia.

    PubMed

    Sotnikova, Marina V; Foronova, Irina V

    2014-08-01

    A lion-like pantherine felid is described as Panthera (Leo) fossilis from the late Early Pleistocene sediments of the Kuznetsk Basin (Western Siberia, Russia). The find of P. fossilis first recorded in Asia considerably extends the current notion of the eastward expansion of the most ancient lions. The Siberian lion is geologically the oldest form and is dimensionally among the largest members of the group of fossil lions on the Eurasian continent. Although known by mandibular remains only, it is readily distinguished from Panthera (Leo) spelaea by a heavy built mandibular corpus with rectangular profile in the cheek teeth area, a deep, well-outlined and narrow anterior section of the masseteric fossa, and a large p4 supported by a big unreduced anterior root. The Siberian lion shares these features with the European Middle Pleistocene P. fossilis and the American Late Pleistocene P. (Leo) atrox, which suggests their close relationship. P. atrox originated from P. fossilis and was isolated in North America south of the Late Pleistocene ice sheets. This explains why the American lion has retained more primitive features than the coeval Eurasian cave lion P. (L.) spelaea.

  10. Human Operations Beyond LEO by the End of the Decade: An Affordable Near-Term "Stepping Stone"

    NASA Technical Reports Server (NTRS)

    Thronson, Harley; Lester, Dan; Talay, Ted

    2010-01-01

    For more than a decade, several teams have assessed designs for a long-duration free-space human habitat beyond low-Earth orbit (LEO), building upon years of hard-won experience with the International Space Station (ISS). These systems would enable multiple achievements for science and human space flight. Most were intended to be deployed using available or near-future capabilities within about a decade after funding begins and serve as the first major human "stepping stone" beyond LEO. Last year, Thronson and Talay summarized work up to that time on expandable or inflatable concepts for deployment at an Earth-Moon (E-M) L1 or L2 location. Here we summarize our team's more recent work both on a long-duration human habitat that could be deployed beyond LEO within a decade and on the priority goals that such a habitat might accomplish. Particulars of this and other concepts for human operations in cis-lunar space are posted on the web and will be presented at professional conferences, and detailed in future publications by our group.

  11. A note on transfers from LEOs to GEOs visiting libration points of the Sun-Earth CRTBP

    NASA Astrophysics Data System (ADS)

    Barrabés, Esther; Garcia-Taberner, Laura; Gómez, Gerard

    2016-02-01

    The objective of this work is to explore the use the invariant manifold dynamics of the Circular Restricted Three Body Problem to construct transfer trajectories from a Low Earth Orbit (LEO) to a Geostationary Earth Orbit (GEO). The underlying idea is to determine orbits that shadow the stable and unstable manifolds of the central manifold of the collinear libration points of the Sun-Earth system, and connect both kinds of orbits around the Earth. The resulting transfer orbits have two legs connected at the libration point region. After a first maneuver performed in the LEO (Δv ≈ 3.1km /s) the spacecraft reaches the neighborhood of the equilibrium point, L1 or L2 , driven by the stable manifold of the central manifold of the point. With a small impulse (Δv ≈ 100m /s), the spacecraft is transferred back to a GEO shadowing an orbit of the unstable manifold of a libration point orbit. Once the GEO is reached, an insertion manoeuvre must be done (Δv ≈ 1.2km /s). In the paper the total Δv , together with the total time of flight, are computed considering initial LEOs with different altitudes and several inclinations and final GEOs with inclinations of ± 5 ° around the equator.

  12. Human Exploration Beyond LEO by the End of the Decade: Designs for Long-Duration "Gateway" Habitats

    NASA Technical Reports Server (NTRS)

    Thronson, Harley; Barr, Jonathan; Budinoff, Jason; Dorsey, John; Gold, Michael; Kutter, Bernard; Lester, Daniel; Moe, Rud; Sauls, Bobby; Spampinato, Phillip; Spexarth, Gary; Sullivan, Gregory; Talay, Ted; Watson, Judith

    2010-01-01

    For the past few years, designs have been developed that are intended to demonstrate that a long-duration habitation system beyond LEO is plausible within several years. Here we summarize a pair of designs with the overriding goal of development and operation beyond LEO before the end of the decade that also build upon experiments and lessons learned from ISS. Both concepts here have the goal of an expandable long-duration habitat at Earth- Moon L1 and/or L2. Both options require subsequent launches for the astronauts. If a heavy-lift launch vehicle is available this decade, an expandable 30.5 mt habitat and departure-stage propulsion system may be launched to E-M L1,2 in a single launch and will offer 575 cubic meter (roughly half the habitable volume of ISS) If existing (or near-future) EELVs are the available launch vehicles this decade, a 16 mt, 170 cubic meter design that uses a pair of launches of Delta IV H and LEO rendezvous/fuel transfer to reach E-M L1,2.

  13. Forwarding techniques for IP fragmented packets in a real 6LoWPAN network.

    PubMed

    Ludovici, Alessandro; Calveras, Anna; Casademont, Jordi

    2011-01-01

    Wireless Sensor Networks (WSNs) are attracting more and more interest since they offer a low-cost solution to the problem of providing a means to deploy large sensor networks in a number of application domains. We believe that a crucial aspect to facilitate WSN diffusion is to make them interoperable with external IP networks. This can be achieved by using the 6LoWPAN protocol stack. 6LoWPAN enables the transmission of IPv6 packets over WSNs based on the IEEE 802.15.4 standard. IPv6 packet size is considerably larger than that of IEEE 802.15.4 data frame. To overcome this problem, 6LoWPAN introduces an adaptation layer between the network and data link layers, allowing IPv6 packets to be adapted to the lower layer constraints. This adaptation layer provides fragmentation and header compression of IP packets. Furthermore, it also can be involved in routing decisions. Depending on which layer is responsible for routing decisions, 6LoWPAN divides routing in two categories: mesh under if the layer concerned is the adaptation layer and route over if it is the network layer. In this paper we analyze different routing solutions (route over, mesh under and enhanced route over) focusing on how they forward fragments. We evaluate their performance in terms of latency and energy consumption when transmitting IP fragmented packets. All the tests have been performed in a real 6LoWPAN implementation. After consideration of the main problems in forwarding of mesh frames in WSN, we propose and analyze a new alternative scheme based on mesh under, which we call controlled mesh under.

  14. Forwarding techniques for IP fragmented packets in a real 6LoWPAN network.

    PubMed

    Ludovici, Alessandro; Calveras, Anna; Casademont, Jordi

    2011-01-01

    Wireless Sensor Networks (WSNs) are attracting more and more interest since they offer a low-cost solution to the problem of providing a means to deploy large sensor networks in a number of application domains. We believe that a crucial aspect to facilitate WSN diffusion is to make them interoperable with external IP networks. This can be achieved by using the 6LoWPAN protocol stack. 6LoWPAN enables the transmission of IPv6 packets over WSNs based on the IEEE 802.15.4 standard. IPv6 packet size is considerably larger than that of IEEE 802.15.4 data frame. To overcome this problem, 6LoWPAN introduces an adaptation layer between the network and data link layers, allowing IPv6 packets to be adapted to the lower layer constraints. This adaptation layer provides fragmentation and header compression of IP packets. Furthermore, it also can be involved in routing decisions. Depending on which layer is responsible for routing decisions, 6LoWPAN divides routing in two categories: mesh under if the layer concerned is the adaptation layer and route over if it is the network layer. In this paper we analyze different routing solutions (route over, mesh under and enhanced route over) focusing on how they forward fragments. We evaluate their performance in terms of latency and energy consumption when transmitting IP fragmented packets. All the tests have been performed in a real 6LoWPAN implementation. After consideration of the main problems in forwarding of mesh frames in WSN, we propose and analyze a new alternative scheme based on mesh under, which we call controlled mesh under. PMID:22346615

  15. Design and Fabrication of DebriSat - A Representative LEO Satellite for Improvements to Standard Satellite Breakup Models

    NASA Technical Reports Server (NTRS)

    Clark, S.; Dietrich, A.; Fitz-Coy, N.; Weremeyer, M.; Liou, J.-C.

    2012-01-01

    This paper discusses the design and fabrication of DebriSat, a 50 kg satellite developed to be representative of a modern low Earth orbit satellite in terms of its components, materials used, and fabrication procedures. DebriSat will be the target of a future hypervelocity impact experiment to determine the physical characteristics of debris generated after an on-orbit collision of a modern LEO satellite. The major ground-based satellite impact experiment used by DoD and NASA in their development of satellite breakup models was SOCIT, conducted in 1992. The target used for that experiment was a Navy transit satellite (40 cm, 35 kg) fabricated in the 1960's. Modern satellites are very different in materials and construction techniques than those built 40 years ago. Therefore, there is a need to conduct a similar experiment using a modern target satellite to improve the fidelity of the satellite breakup models. To ensure that DebriSat is truly representative of typical LEO missions, a comprehensive study of historical LEO satellite designs and missions within the past 15 years for satellites ranging from 1 kg to 5000 kg was conducted. This study identified modern trends in hardware, material, and construction practices utilized in recent LEO missions. Although DebriSat is an engineering model, specific attention is placed on the quality, type, and quantity of the materials used in its fabrication to ensure the integrity of the outcome. With the exception of software, all other aspects of the satellite s design, fabrication, and assembly integration and testing will be as rigorous as that of an actual flight vehicle. For example, to simulate survivability of launch loads, DebriSat will be subjected to a vibration test. As well, the satellite will undergo thermal vacuum tests to verify that the components and overall systems meet typical environmental standards. Proper assembly and integration techniques will involve comprehensive joint analysis, including the precise

  16. ALFALFA Discovery of the nearby Gas-rich Dwarf Galaxy Leo P. III. An Extremely Metal Deficient Galaxy

    NASA Astrophysics Data System (ADS)

    Skillman, Evan D.; Salzer, John J.; Berg, Danielle A.; Pogge, Richard W.; Haurberg, Nathalie C.; Cannon, John M.; Aver, Erik; Olive, Keith A.; Giovanelli, Riccardo; Haynes, Martha P.; Adams, Elizabeth A. K.; McQuinn, Kristen B. W.; Rhode, Katherine L.

    2013-07-01

    We present KPNO 4 m and LBT/MODS spectroscopic observations of an H II region in the nearby dwarf irregular galaxy Leo P discovered recently in the Arecibo ALFALFA survey. In both observations, we are able to accurately measure the temperature sensitive [O III] λ4363 line and determine a "direct" oxygen abundance of 12 + log(O/H) = 7.17 ± 0.04. Thus, Leo P is an extremely metal deficient (XMD) galaxy, and, indeed, one of the most metal deficient star-forming galaxies ever observed. For its estimated luminosity, Leo P is consistent with the relationship between luminosity and oxygen abundance seen in nearby dwarf galaxies. Leo P shows normal α element abundance ratios (Ne/O, S/O, and Ar/O) when compared to other XMD galaxies, but elevated N/O, consistent with the "delayed release" hypothesis for N/O abundances. We derive a helium mass fraction of 0.2509^{+0.0184}_{-0.0123}, which compares well with the WMAP + BBN prediction of 0.2483 ± 0.0002 for the primordial helium abundance. We suggest that surveys of very low mass galaxies compete well with emission line galaxy surveys for finding XMD galaxies. It is possible that XMD galaxies may be divided into two classes: the relatively rare XMD emission line galaxies which are associated with starbursts triggered by infall of low-metallicity gas and the more common, relatively quiescent XMD galaxies like Leo P, with very low chemical abundances due to their intrinsically small masses. Some of the observations reported here were obtained at the LBT Observatory. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The

  17. Lion (Panthera leo) populations are declining rapidly across Africa, except in intensively managed areas.

    PubMed

    Bauer, Hans; Chapron, Guillaume; Nowell, Kristin; Henschel, Philipp; Funston, Paul; Hunter, Luke T B; Macdonald, David W; Packer, Craig

    2015-12-01

    We compiled all credible repeated lion surveys and present time series data for 47 lion (Panthera leo) populations. We used a Bayesian state space model to estimate growth rate-λ for each population and summed these into three regional sets to provide conservation-relevant estimates of trends since 1990. We found a striking geographical pattern: African lion populations are declining everywhere, except in four southern countries (Botswana, Namibia, South Africa, and Zimbabwe). Population models indicate a 67% chance that lions in West and Central Africa decline by one-half, while estimating a 37% chance that lions in East Africa also decline by one-half over two decades. We recommend separate regional assessments of the lion in the World Conservation Union (IUCN) Red List of Threatened Species: already recognized as critically endangered in West Africa, our analysis supports listing as regionally endangered in Central and East Africa and least concern in southern Africa. Almost all lion populations that historically exceeded ∼ 500 individuals are declining, but lion conservation is successful in southern Africa, in part because of the proliferation of reintroduced lions in small, fenced, intensively managed, and funded reserves. If management budgets for wild lands cannot keep pace with mounting levels of threat, the species may rely increasingly on these southern African areas and may no longer be a flagship species of the once vast natural ecosystems across the rest of the continent.

  18. Mycobacterium bovis infection in the lion (Panthera leo): Current knowledge, conundrums and research challenges.

    PubMed

    Viljoen, Ignatius M; van Helden, Paul D; Millar, Robert P

    2015-06-12

    Mycobacterium bovis has global public-health and socio-economic significance and can infect a wide range of species including the lion (Panthera leo) resulting in tuberculosis. Lions are classified as vulnerable under the IUCN Red List of Threatened Species and have experienced a 30% population decline in the past two decades. However, no attempt has been made to collate and critically evaluate the available knowledge of M. bovis infections in lions and potential effects on population. In this review we set out to redress this. Arguments suggesting that ingestion of infected prey animals are the main route of infection for lions have not been scientifically proven and research is needed into other possible sources and routes of infection. The paucity of knowledge on host susceptibility, transmission directions and therefore host status, manifestation of pathology, and epidemiology of the disease in lions also needs to be addressed. Advances have been made in diagnosing the presence of M. bovis in lions. However, these diagnostic tests are unable to differentiate between exposure, presence of infection, or stage of disease. Furthermore, there are contradictory reports on the effects of M. bovis on lion populations with more data needed on disease dynamics versus the lion population's reproductive dynamics. Knowledge on disease effects on the lion reproduction and how additional stressors such as drought or co-morbidities may interact with tuberculosis is also lacking. Filling these knowledge gaps will contribute to the understanding of mycobacterial infections and disease in captive and wild lions and assist in lion conservation endeavours.

  19. Polymorphic expression in the CD8alpha chain surface receptor of African lions (Panthera leo).

    PubMed

    Bull, Marta E; Gebhard, Douglas G; Tompkins, Wayne A F; Kennedy-Stoskopf, Suzanne

    2002-01-15

    Free-ranging African lion (Panthera leo) peripheral blood mononuclear cells (PBMC) were examined using flow cytometry and antibodies developed for use in the domestic cat to determine if phenotypic changes occurred in lion lymphocytes as a result of feline immunodeficiency virus (FIV) infection. The percentage of CD8 cells from lion peripheral blood was considerably lower than in the domestic cat. Lions with elevated levels of CD8+ cells were typically infected with FIV, similar to observations in the domestic cat. Antibodies against the alpha chain of the CD8 receptor (monoclonal antibody (mAb) 3.357) did not react consistently in all lions examined. Flow cytometric analysis determined that approximately 82 and 80% of the animals from Kruger and Hluhluwe-Umfolozi National Parks in South Africa reacted with the monoclonal antibody against the alpha chain of CD8 receptor, while only 17% of the lions in Etosha National Park in Namibia cross-reacted with the CD8alpha chain. There was no apparent correlation between FIV status and CD8alpha chain reactivity. The relative isolation of Etosha from the other two parks could explain the marked difference in CD8alpha chain expression and suggests that lions similar to other mammalian species demonstrate polymorphic expression of the CD8alpha chain (197).

  20. Lion (Panthera leo) populations are declining rapidly across Africa, except in intensively managed areas.

    PubMed

    Bauer, Hans; Chapron, Guillaume; Nowell, Kristin; Henschel, Philipp; Funston, Paul; Hunter, Luke T B; Macdonald, David W; Packer, Craig

    2015-12-01

    We compiled all credible repeated lion surveys and present time series data for 47 lion (Panthera leo) populations. We used a Bayesian state space model to estimate growth rate-λ for each population and summed these into three regional sets to provide conservation-relevant estimates of trends since 1990. We found a striking geographical pattern: African lion populations are declining everywhere, except in four southern countries (Botswana, Namibia, South Africa, and Zimbabwe). Population models indicate a 67% chance that lions in West and Central Africa decline by one-half, while estimating a 37% chance that lions in East Africa also decline by one-half over two decades. We recommend separate regional assessments of the lion in the World Conservation Union (IUCN) Red List of Threatened Species: already recognized as critically endangered in West Africa, our analysis supports listing as regionally endangered in Central and East Africa and least concern in southern Africa. Almost all lion populations that historically exceeded ∼ 500 individuals are declining, but lion conservation is successful in southern Africa, in part because of the proliferation of reintroduced lions in small, fenced, intensively managed, and funded reserves. If management budgets for wild lands cannot keep pace with mounting levels of threat, the species may rely increasingly on these southern African areas and may no longer be a flagship species of the once vast natural ecosystems across the rest of the continent. PMID:26504235

  1. Influence of the ionospheric model on DCB computation and added value of LEO satellites

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Lestarquit, Laurent; Loyer, Sylvain; Mercier, Flavien; Perosanz, Félix

    2016-04-01

    In order to compute inter-frequency Differential Code Biases (DCBs), the Geometry-Free combination of a GNSS signal pair needs to be corrected from the ionospheric refraction effect. Such information is obtained using either Global Ionospheric Maps (GIMs) or local models. In this work we investigate the influence of GIMs on the final value and precision of DCB solution. The study covers different ionospheric conditions, ranging from very quiet ionospheric background up to a severe ionospheric storm. In a first step, the Slant Total Electron Content (STEC) between GIMs is assessed as a function of receiver latitude, elevation mask and ionospheric conditions. Then, daily DCBs are estimated using these different GIMs, receiver and satellite contributions being separated using a zero-mean constraint. If the precision of satellite DCBs is clearly dependent on ionospheric conditions and of the observing network, the choice of the GIM seems also to have a non negligible impact. At last, an independent estimation of DCBs is performed using Low Earth Orbit (LEO) observations (such as JASON's GPS data). This solution is compared with our ground network solution and with DCBs coming from the International GNSS Service.

  2. Effect of LEO Exposure on Aromatic Polymers Containing Phenylphosphine Oxide Groups

    NASA Technical Reports Server (NTRS)

    Watson, K. A.; Ghose, S.; Lillehei, P. T.; Smith, J. G., Jr.; Connell, J. W.

    2007-01-01

    As part of the Materials on The International Space Station Experiment (MISSE), aromatic polymers containing phenylphosphine oxide groups were exposed to low Earth orbit (LEO) for approximately 4 years. All of the aromatic polymers containing phenylphosphine oxide groups survived the exposure despite the high fluence of atomic oxygen that completely eroded other polymer films such as Kapton and Mylar of comparable or greater thickness. The samples consisted of a colorless polyimide film and a poly(arylene ether benzimidazole) film and thread. The samples were characterized for changes in physical properties, thermal/optical properties (i.e. solar absorptivity and thermal emissivity), surface chemistry (X-ray photoelectron spectroscopy), and surface topography (atomic force microscopy). The data from the polymer samples on MISSE were compared to samples from the same batch of material stored under ambient conditions on Earth. In addition, comparisons were made between the MISSE samples and those subjected to shorter term space flight exposures. The results of these analyses will be presented.

  3. Mucoperiosteal exostoses in the tympanic bulla of African lions (Panthera leo).

    PubMed

    Novales, M; Ginel, P J; Diz, A; Blanco, B; Zafra, R; Guerra, R; Mozos, E

    2015-03-01

    Mucoperiosteal exostoses (MpEs) of the tympanic bulla (TB), also referred as middle-ear otoliths, have been occasionally described in dogs and cats in association with clinical signs of otitis media or as an incidental finding, but they have not been recorded in other species. In this report, we describe the radiographic, gross, and histopathologic features of MpEs in 8 African lions (Panthera leo). All animals (5 males and 3 females) were adults that had been kept in captivity and had their skeletons conserved as part of an anatomic academic collection. A radiographic study revealed mineralized structures in the TB consistent with MpEs in 7 of the 16 examined TB; a computed tomography study identified MpEs in 12 of the 16 TB. Six TB from 4 lions were sectioned, and several MpEs were demineralized for histopathologic analysis. Grossly, MpEs appeared variable in number and shape. Some were globular structures that were loosely attached to the mucosal surface of the TB; others were isolated to coalescent bone spicules extending from the mucoperiosteum. Position was also variable, but MpEs frequently developed in the hypotympanum, especially on the ventromedial aspect of the TB wall. Microscopically, MpEs were composed of osteonal bone growing from the periosteum and not by dystrophic calcification of necrotic tissue debris, as is hypothesized in dogs.

  4. Near-Real Time Cloud Properties and Aircraft Icing Indices from GEO and LEO Satellites

    NASA Technical Reports Server (NTRS)

    Minnis, Patrick; Smith, William L., Jr.; Nguyen, Louis; Spangenberg, D. A.; Heck, Patrick W.; Palikonda, Rabindra; Ayers, J. Kirk; Wolff, Cory; Murray, John J.

    2004-01-01

    Imagers on many of the current and future operational meteorological satellites in geostationary Earth orbit (GEO) and lower Earth orbit (LEO) have enough spectral channels to derive cloud microphysical properties useful for a variety of applications. The products include cloud amount, phase, optical depth, temperature, height and pressure, thickness, effective particle size, and ice or liquid water path, shortwave albedo, and outgoing longwave radiation for each imager pixel. Because aircraft icing depends on cloud temperature, droplet size, and liquid water content as well as aircraft variables, it is possible to estimate the potential icing conditions from the cloud phase, temperature, effective droplet size, and liquid water path. A prototype icing index is currently being derived over the contiguous USA in near-real time from Geostationary Operational Environmental Satellite (GOES-10 and 12) data on a half-hourly basis and from NOAA- 16 Advanced Very High Resolution (AVHRR) data when available. Because the threshold-based algorithm is sensitive to small errors and differences in satellite imager and icing is complex process, a new probability based icing diagnosis technique is developed from a limited set of pilot reports. The algorithm produces reasonable patterns of icing probability and intensities when compared with independent model and pilot report data. Methods are discussed for improving the technique for incorporation into operational icing products.

  5. Selected clinical, biochemical, and electrolyte alterations in anesthetized captive tigers (Panthera tigris) and lions (Panthera leo).

    PubMed

    Reilly, Sabrina; Seddighi, M Reza; Steeil, James C; Sura, Patricia; Whittemore, Jacqueline C; Gompf, Rebecca E; Elliott, Sarah B; Ramsay, Edward C

    2014-06-01

    A prospective study to assess changes in selected plasma biochemistry and electrolyte values, plasma insulin and aldosterone concentrations, and electrocardiography (ECG) was performed on eight female captive tigers (Panthera tigris) and three lions (Panthera leo) undergoing general anesthesia for elective laparoscopic ovariectomy. Each animal was sedated with medetomidine (18-25 microg/kg) and midazolam (0.06-0.1 mg/kg) intramuscularly, and anesthesia was induced with ketamine (1.9-3.5 mg/kg) intramuscularly and maintained with isoflurane. Venous blood samples were collected and analyzed for plasma biochemistry parameters and insulin and aldosterone concentrations. An ECG was recorded at the time of each blood sample collection. Mean plasma potassium, glucose, phosphorus, and aldosterone concentrations increased during anesthesia (P < or = 0.05). One tiger developed hyperkalemia (6.5 mmol/L) 2.5 hr after anesthetic induction. Plasma insulin concentrations were initially below the low end of the domestic cat reference interval (72-583 pmol/L), but mean insulin concentration increased (P < or = 0.05) over time compared with the baseline values. Three tigers and two lions had ECG changes that were representative of myocardial hypoxemia. Based on these results, continuous monitoring of clinical and biochemical alterations during general anesthesia in large nondomestic felids is warranted, and consideration should be given to reversal of medetomidine in these animals should significant changes in electrolytes or ECG occur.

  6. A Novel Twin-TLD Radiation Dosimeter for Astronauts during LEO Missions

    NASA Astrophysics Data System (ADS)

    Mukherjee, Bhaskar; Lambert, Jamil; Fuentes, Carolina; Sunil, C.; Tripathy, Sam; Sarkar, Pradip Kumar

    2012-07-01

    During low earth orbiting (LEO) missions space vehicles are continuously bombarded with energetic protons from the sun and in the events of solar flare (SFE), the proton flux sporadically increases by many orders of magnitudes. The solar protons interact with the containment wall of the vehicle producing high-energy neutrons with a broad energy distribution as well as gamma rays, which result in a high radiation exposure to astronauts. By implementing pairs of TLD-700 (7LiF:Ti, Mg) and TLD-500 (alpha: Al2O3-C) chips we have developed a personal dosimeter for an accurate assessment of biological dose of high-energy mixed radiation field. Dosimeters were irradiated with high-energy neutrons produced by bombarding a 25*25*35 cm3 polystyrene plate phantom with high-energy therapeutic protons at Westdeutsches Protonentherapiezentrum Essen (WPE). The radiation field was simulated using the FLUKA code and the dosimeters were calibrated in-situ with a tissue equivalent proportional counter (TEPC). The operation principle of the novel twin-TLD personal dosimeter for astronauts will be highlighted in our presentation.

  7. [The Book of the Eparch, by Leo VI: interest for the history of pharmacy].

    PubMed

    Lafont, Olivier

    2005-01-01

    In 1893, Jules Nicole discovered a greek manuscript, named Genevensis 23, which proved to be the Book of the Eparch. This document contained the regulations for trade guilds in Constantinople, at the end of the IXth century and the beginning of the Xth century. It had been published by Emperor Leo VI, who reigned upon the Byzantine Empire from 886 to 911. Three professions mentioned in this book have some interest for history of pharmacy: wax chandlers, spicers and perfumers. The differences between spicers and perfumers consisted in the kind of products they sold and in the way they weighed these products. Spicers were, at the time, far from pharmacy, because they sold mainly food and no spices, while the perfumers dealt with spices and perfumes. Anyway, none of these professions was involved in preparing medicines. No mention was made of pigmentarioi in the Book of the Eparch and that raised the question of the part really played by these so-called "pigment makers" in the preparation and the dispensation of medicines. The role of physicians remained preeminent in supplying patients with drugs.

  8. Evaluation of microsatellite markers for populations studies and forensic identification of African lions (Panthera leo).

    PubMed

    Miller, Susan M; Harper, Cindy K; Bloomer, Paulette; Hofmeyr, Jennifer; Funston, Paul J

    2014-01-01

    The South African lion (Panthera leo) population is highly fragmented. One-third of its wild lions occur in small (<1000 km(2)) reserves. These lions were reintroduced from other areas of the species' historical range. Management practices on these reserves have not prioritized genetic provenance or heterozygosity. These trends potentially constrain the conservation value of these lions. To ensure the best management and long-term survival of these subpopulations as a viable collective population, the provenance and current genetic diversity must be described. Concurrently, poaching of lions to supply a growing market for lion bones in Asia may become a serious conservation challenge in the future. Having a standardized, validated method for matching confiscated lion parts with carcasses will be a key tool in investigating these crimes. We evaluated 28 microsatellites in the African lion using samples from 18 small reserves and 1 captive facility in South Africa, two conservancies in Zimbabwe, and Kruger National and Kgalagadi Transfrontier Parks to determine the loci most suited for population management and forensic genetic applications. Twelve microsatellite loci with a match probability of 1.1×10(-5) between siblings were identified for forensics. A further 10 could be added for population genetics studies.

  9. Genetic Evidence for Contrasting Wetland and Savannah Habitat Specializations in Different Populations of Lions (Panthera leo).

    PubMed

    Moore, Andy E; Cotterill, Fenton P D Woody; Winterbach, Christiaan W; Winterbach, Hanlie E K; Antunes, Agostinho; O'Brien, Stephen J

    2016-03-01

    South-central Africa is characterized by an archipelago of wetlands, which has evolved in time and space since at least the Miocene, providing refugia for animal species during Pleistocene arid episodes. Their importance for biodiversity in the region is reflected in the evolution of a variety of specialist mammal and bird species, adapted to exploit these wetland habitats. Populations of lions (Panthera leo) across south-central and east Africa have contrasting signatures of mitochondrial DNA haplotypes and biparental nuclear DNA in wetland and savannah habitats, respectively, pointing to the evolution of distinct habitat preferences. This explains the absence of genetic admixture of populations from the Kalahari savannah of southwest Botswana and the Okavango wetland of northern Botswana, despite separation by only 500 km. We postulate that ancestral lions were wetland specialists and that the savannah lions evolved from populations that were isolated during arid Pleistocene episodes. Expansion of grasslands and the resultant increase in herbivore populations during mesic Pleistocene climatic episodes provided the stimulus for the rapid population expansion and diversification of the highly successful savannah lion specialists. Our model has important implications for lion conservation.

  10. Lions (Panthera leo) solve, learn, and remember a novel resource acquisition problem.

    PubMed

    Borrego, Natalia; Dowling, Brian

    2016-09-01

    The social intelligence hypothesis proposes that the challenges of complex social life bolster the evolution of intelligence, and accordingly, advanced cognition has convergently evolved in several social lineages. Lions (Panthera leo) offer an ideal model system for cognitive research in a highly social species with an egalitarian social structure. We investigated cognition in lions using a novel resource task: the suspended puzzle box. The task required lions (n = 12) to solve a novel problem, learn the techniques used to solve the problem, and remember techniques for use in future trials. The majority of lions demonstrated novel problem-solving and learning; lions (11/12) solved the task, repeated success in multiple trials, and significantly reduced the latency to success across trials. Lions also demonstrated cognitive abilities associated with memory and solved the task after up to a 7-month testing interval. We also observed limited evidence for social facilitation of the task solution. Four of five initially unsuccessful lions achieved success after being partnered with a successful lion. Overall, our results support the presence of cognition associated with novel problem-solving, learning, and memory in lions. To date, our study is only the second experimental investigation of cognition in lions and further supports expanding cognitive research to lions.

  11. Diagnosis and treatment of a dermal malignant melanoma in an African lion (Panthera leo).

    PubMed

    Steeil, James C; Schumacher, Juergen; Baine, Katherine; Ramsay, Edward C; Sura, Patricia; Hodshon, Rebecca; Donnell, Robert L; Lee, Nathan D

    2013-09-01

    A 13-yr-old intact male African lion (Panthera leo) presented with a 4-mo history of left maxillary lip swelling. On physical examination, a 10-cm-diameter, ulcerated, round, firm, and pigmented mass at the level of the left maxillary canine tooth was noticed. All other organ systems examined were within normal limits. Multiple biopsies of the mass were collected and fixed in 10% neutral buffered formalin. Histopathologic evaluation of the biopsies revealed a malignant dermal melanoma. Hematologic and plasma biochemical parameters were within normal reference ranges. Thoracic radiographs taken 3 days following initial presentation showed no evidence of metastasis of the tumor. Computed tomography of the skull and neck was performed to evaluate local tumor invasion and to plan for hypofractionated radiation therapy. Therapy included four weekly treatments of 8 gray external-beam hypofractionated radiation and four bimonthly immunotherapy treatments. Following this treatment regime, the tumor size was reduced by 50%, and surgical excision was performed. No major side effects associated with radiation or immunotherapy were seen. Six months after diagnosis, hematologic and plasma biochemical parameters were within normal limits, thoracic radiographs showed no evidence of metastasis, and the lion showed no clinical signs of disease. The lion will continue to receive immunotherapy every 6 mo for the rest of its life. To the authors' knowledge, this is the first report of a successful treatment of a malignant dermal melanoma with external-beam hypofractionated radiation, immunotherapy, and surgical excision in an African lion.

  12. Survivability to Hypervelocity Impacts of Electrodynamic Tape Tethers for Deorbiting Spacecraft in LEO

    NASA Astrophysics Data System (ADS)

    Francesconi, A.; Giacomuzzo, C.; Lorenzini, E. C.

    2013-08-01

    This paper reports the results of 16 hypervelocity impact experiments on a composite flat electrodynamic tether for LEO spacecraft end-of-life deorbiting. The system is being developed within the EU FP7 BETs program. Impact tests were carried out at CISAS impact facility, with the aim of deriving failure equations that include the impact angle dependence up to grazing incidence. Experiments were realised with 1.5 and 2.3 mm aluminium spheres, at velocities between 3 and 5 km/s and impact angle from 0° to 90° from the tape normal. After a preliminary post-impact inspection of the target, the damage extension on the tape was evaluated using an automatic image processing technique. Ballistic limit equations were developed in the experimental range using a procedure that allows to estimate the uncertainty in the failure predictions starting from the measurement of the damage area. Experiments showed that the impact damage is very close to the projectile size in case of normal impact, while it increases significantly at highly oblique impact angles.

  13. Ultra-weak magnetic fields in Am stars: β UMa and θ Leo

    NASA Astrophysics Data System (ADS)

    Blazère, A.; Petit, P.; Lignières, F.; Aurière, M.; Ballot, J.; Böhm, T.; Folsom, C.; Ariste, A. López; Wade, G. A.

    2015-10-01

    An extremely weak circularly-polarized signature was recently detected in the spectral lines of the Am star Sirius A. With a prominent positive lobe, the shape of the phase-averaged Stokes V line profile is atypical of stellar Zeeman signatures, casting doubts on its magnetic origin. We report here on ultra-deep spectropolarimetric observations of two more bright Am stars: β Uma and θ Leo. Stokes V line signatures are detected in both objects, with a shape and amplitude similar to the one observed on Sirius A. We demonstrate that the amplitude of the Stokes V line profiles depend on various line parameters (Landé factor, wavelength, depth) as expected from a Zeeman signature, confirming that extremely weak magnetic fields are likely present in a large fraction of Am stars. We suggest that the strong asymmetry of the polarized signatures, systematically observed so far in Am stars and never reported in strongly magnetic Ap stars, bears unique information about the structure and dynamics of the thin surface convective shell of Am stars.

  14. Selected clinical, biochemical, and electrolyte alterations in anesthetized captive tigers (Panthera tigris) and lions (Panthera leo).

    PubMed

    Reilly, Sabrina; Seddighi, M Reza; Steeil, James C; Sura, Patricia; Whittemore, Jacqueline C; Gompf, Rebecca E; Elliott, Sarah B; Ramsay, Edward C

    2014-06-01

    A prospective study to assess changes in selected plasma biochemistry and electrolyte values, plasma insulin and aldosterone concentrations, and electrocardiography (ECG) was performed on eight female captive tigers (Panthera tigris) and three lions (Panthera leo) undergoing general anesthesia for elective laparoscopic ovariectomy. Each animal was sedated with medetomidine (18-25 microg/kg) and midazolam (0.06-0.1 mg/kg) intramuscularly, and anesthesia was induced with ketamine (1.9-3.5 mg/kg) intramuscularly and maintained with isoflurane. Venous blood samples were collected and analyzed for plasma biochemistry parameters and insulin and aldosterone concentrations. An ECG was recorded at the time of each blood sample collection. Mean plasma potassium, glucose, phosphorus, and aldosterone concentrations increased during anesthesia (P < or = 0.05). One tiger developed hyperkalemia (6.5 mmol/L) 2.5 hr after anesthetic induction. Plasma insulin concentrations were initially below the low end of the domestic cat reference interval (72-583 pmol/L), but mean insulin concentration increased (P < or = 0.05) over time compared with the baseline values. Three tigers and two lions had ECG changes that were representative of myocardial hypoxemia. Based on these results, continuous monitoring of clinical and biochemical alterations during general anesthesia in large nondomestic felids is warranted, and consideration should be given to reversal of medetomidine in these animals should significant changes in electrolytes or ECG occur. PMID:25000694

  15. Radiation exposure and performance of multiple burn LEO-GEO orbit transfer trajectories

    NASA Technical Reports Server (NTRS)

    Gorland, S. H.

    1985-01-01

    Many potential strategies exist for the transfer of spacecraft from low Earth orbit (LEO) to geosynchronous (GEO) orbit. One strategy has generally been utilized, that being a single impulsive burn at perigee and a GEO insertion burn at apogee. Multiple burn strategies were discussed for orbit transfer vehicles (OTVs) but the transfer times and radiation exposure, particularly for potentially manned missions, were used as arguments against those options. Quantitative results concerning the trip time and radiation encountered by multiple burn orbit transfer missions in order to establish the feasibility of manned missions, the vulnerability of electronics, and the shielding requirements are presented. The performance of these multiple burn missions is quantified in terms of the payload and propellant variances from the minimum energy mission transfer. The missions analyzed varied from one to eight perigee burns and ranged from a high thrust, 1 g acceleration, cryogenic hydrogen-oxygen chemical prpulsion system to a continuous burn, 0.001 g acceleration, hydrogen fueled resistojet propulsion system with a trip time of 60 days.

  16. Radiation exposure and performance of multiple burn LEO-GEO orbit transfer trajectories

    NASA Technical Reports Server (NTRS)

    Gorland, S. H.

    1985-01-01

    Many potential strategies exist for the transfer of spacecraft from low Earth orbit (LEO) to geosynchronous (GEO) orbit. One strategy has generally been utilized, that being a single impulsive burn at perigee and a GEO insertion burn at apogee. Multiple burn strategies were discussed for orbit transfer vehicles (OTVs) but the transfer times and radiation exposure, particularly for potentially manned missions, were used as arguments against those options. Quantitative results concerning the trip time and radiation encountered by multiple burn orbit transfer missions in order to establish the feasibility of manned missions, the vulnerability of electronics, and the shielding requirements are presented. The performance of these multiple burn missions is quantified in terms of the payload and propellant variances from the minimum energy mission transfer. The missions analyzed varied from one to eight perigee burns and ranged from a high thrust, 1 g, acceleration, cryogenic hydrogen-oxygen chemical propulsion system for a continuous burn, 0.001 g acceleration, hydrogen, fueled resistojet propulsion system with a trip time of 60 days.

  17. Analysis of MIR-18 results for physical and biological dosimetry: radiation shielding effectiveness in LEO.

    PubMed

    Cucinotta, F A; Wilson, J W; Williams, J R; Dicello, J F

    2000-06-01

    We compare models of radiation transport and biological response to physical and biological dosimetry results from astronauts on the Mir space station. Transport models are shown to be in good agreement with physical measurements and indicate that the ratio of equivalent dose from the Galactic Cosmic Rays (GCR) to protons is about 3/2:1 and that this ratio will increase for exposures to internal organs. Two biological response models are used to compare to the Mir biodosimetry for chromosome aberration in lymphocyte cells; a track-structure model and the linear-quadratic model with linear energy transfer (LET) dependent weighting coefficients. These models are fit to in vitro data for aberration formation in human lymphocytes by photons and charged particles. Both models are found to be in reasonable agreement with data for aberrations in lymphocytes of Mir crew members: however there are differences between the use of LET dependent weighting factors and track structure models for assigning radiation quality factors. The major difference in the models is the increased effectiveness predicted by the track model for low charge and energy ions with LET near 10 keV/micrometers. The results of our calculations indicate that aluminum shielding, although providing important mitigation of the effects of trapped radiation, provides no protective effect from the galactic cosmic rays (GCR) in low-earth orbit (LEO) using either equivalent dose or the number of chromosome aberrations as a measure until about 100 g/cm 2 of material is used. PMID:11543368

  18. Revisiting the Local Leo Cold Cloud and Revised Constraints on the Local Hot Bubble

    NASA Astrophysics Data System (ADS)

    Snowden, S. L.; Heiles, C.; Koutroumpa, D.; Kuntz, K. D.; Lallement, R.; McCammon, D.; Peek, J. E. G.

    2015-06-01

    The Local Leo Cold Cloud (LLCC, at a distance of 11–24 pc) was studied in its relation to the Local Hot Bubble (LHB) and the result suggested that much of the observed 1/4 keV emission in that direction originates in front of the cloud. This placed a strong constraint on the distribution of X-ray emission within the LHB and called into question the assumption of a uniform distribution of X-ray emitting plasma within the Local Cavity. However, recent work has quantified the contribution of heliospheric solar wind charge exchange (SWCX) emission to the diffuse X-ray background measured by the ROSAT All-Sky Survey (RASS) at 1/4 keV, and led to the consistency of pressure measurements between the LHB and the local cloud component of the complex of local interstellar clouds (CLICs) surrounding the Sun. In this paper we revisit the LLCC and improve the previous analysis by using higher resolution RASS data, a serendipitous ROSAT pointed observation, a rigorous treatment of the band-averaged X-ray absorption cross section, and models for the heliospheric and magnetospheric SWCX contributions. We find that the foreground emission to the cloud is in excess of the expected heliospheric (interplanetary plus near Earth) SWCX contribution but that it is marginally consistent with the range of possible LHB plasma path lengths between the LLCC and the CLICs given the currently understood plasma emissivity.

  19. Unraveling the mysteries of the Leo Ring: An absorption line study of an unusual gas cloud

    SciTech Connect

    Rosenberg, J. L.; Haislmaier, Karl; Giroux, M. L.; Keeney, B. A.; Schneider, S. E.

    2014-07-20

    Since the discovery of the large (2 × 10{sup 9} M{sub ☉}) intergalactic cloud known as the Leo Ring in the 1980s, the origin of this object has been the center of a lively debate. Determining the origin of this object is still important as we develop a deeper understanding of the accretion and feedback processes that shape galaxy evolution. We present Hubble Space Telescope/Cosmic Origins Spectrograph observations of three sightlines near the ring, two of which penetrate the high column density neutral hydrogen gas visible in 21 cm observations of the object. These observations provide the first direct measurement of the metallicity of the gas in the ring, an important clue to its origin. Our best estimate of the metallicity of the ring is ∼10% Z{sub ☉}, higher than expected for primordial gas but lower than expected from an interaction. We discuss possible modifications to the interaction and primordial gas scenarios that would be consistent with this metallicity measurement.

  20. Lion (Panthera leo) populations are declining rapidly across Africa, except in intensively managed areas

    PubMed Central

    Bauer, Hans; Chapron, Guillaume; Nowell, Kristin; Henschel, Philipp; Funston, Paul; Macdonald, David W.; Packer, Craig

    2015-01-01

    We compiled all credible repeated lion surveys and present time series data for 47 lion (Panthera leo) populations. We used a Bayesian state space model to estimate growth rate-λ for each population and summed these into three regional sets to provide conservation-relevant estimates of trends since 1990. We found a striking geographical pattern: African lion populations are declining everywhere, except in four southern countries (Botswana, Namibia, South Africa, and Zimbabwe). Population models indicate a 67% chance that lions in West and Central Africa decline by one-half, while estimating a 37% chance that lions in East Africa also decline by one-half over two decades. We recommend separate regional assessments of the lion in the World Conservation Union (IUCN) Red List of Threatened Species: already recognized as critically endangered in West Africa, our analysis supports listing as regionally endangered in Central and East Africa and least concern in southern Africa. Almost all lion populations that historically exceeded ∼500 individuals are declining, but lion conservation is successful in southern Africa, in part because of the proliferation of reintroduced lions in small, fenced, intensively managed, and funded reserves. If management budgets for wild lands cannot keep pace with mounting levels of threat, the species may rely increasingly on these southern African areas and may no longer be a flagship species of the once vast natural ecosystems across the rest of the continent. PMID:26504235

  1. Model-Based GN and C Simulation and Flight Software Development for Orion Missions beyond LEO

    NASA Technical Reports Server (NTRS)

    Odegard, Ryan; Milenkovic, Zoran; Henry, Joel; Buttacoli, Michael

    2014-01-01

    For Orion missions beyond low Earth orbit (LEO), the Guidance, Navigation, and Control (GN&C) system is being developed using a model-based approach for simulation and flight software. Lessons learned from the development of GN&C algorithms and flight software for the Orion Exploration Flight Test One (EFT-1) vehicle have been applied to the development of further capabilities for Orion GN&C beyond EFT-1. Continuing the use of a Model-Based Development (MBD) approach with the Matlab®/Simulink® tool suite, the process for GN&C development and analysis has been largely improved. Furthermore, a model-based simulation environment in Simulink, rather than an external C-based simulation, greatly eases the process for development of flight algorithms. The benefits seen by employing lessons learned from EFT-1 are described, as well as the approach for implementing additional MBD techniques. Also detailed are the key enablers for improvements to the MBD process, including enhanced configuration management techniques for model-based software systems, automated code and artifact generation, and automated testing and integration.

  2. Leo Eitinger MD: tribute to a Holocaust survivor, humane physician and friend of mankind.

    PubMed

    Chelouche, Tessa

    2014-04-01

    Born in Czechoslovakia, psychiatrist Leo Eitinger (1912-1996) became internationally recognized for research on his fellow concentration camp inmates. He graduated as an MD in 1937, but being Jewish was prohibited from practicing as a doctor. When the Nazis occupied the area he was forced to flee to Norway, where in 1940 he was again deprived of his right to practice medicine. In 1942 he was arrested and deported to Auschwitz. There, as a physician inmate, he was able to help and in many cases save his fellow prisoners, not only with his medical skills but by falsifying prisoners' documents and hiding them from their Nazi captors. One of his patients was Elie Wiesel. Eitinger survived the camps but was forced to join a "death march." After the war he resumed medical practice in Norway, specializing in psychiatry. With his personal experience and knowledge of the suffering of camp survivors, he dedicated his life to studying the psychological effects of traumatic stress in different groups. Eitinger's academic contributions were crucial in the development of this area of research--namely, the effects of excessive stress, laying the foundations for the definition of post-traumatic stress disorder and the post-concentration camp syndrome, thus facilitating recognition of the medical and psychological post-war conditions of the survivors and their resultant disability pensions.

  3. Lions (Panthera leo) solve, learn, and remember a novel resource acquisition problem.

    PubMed

    Borrego, Natalia; Dowling, Brian

    2016-09-01

    The social intelligence hypothesis proposes that the challenges of complex social life bolster the evolution of intelligence, and accordingly, advanced cognition has convergently evolved in several social lineages. Lions (Panthera leo) offer an ideal model system for cognitive research in a highly social species with an egalitarian social structure. We investigated cognition in lions using a novel resource task: the suspended puzzle box. The task required lions (n = 12) to solve a novel problem, learn the techniques used to solve the problem, and remember techniques for use in future trials. The majority of lions demonstrated novel problem-solving and learning; lions (11/12) solved the task, repeated success in multiple trials, and significantly reduced the latency to success across trials. Lions also demonstrated cognitive abilities associated with memory and solved the task after up to a 7-month testing interval. We also observed limited evidence for social facilitation of the task solution. Four of five initially unsuccessful lions achieved success after being partnered with a successful lion. Overall, our results support the presence of cognition associated with novel problem-solving, learning, and memory in lions. To date, our study is only the second experimental investigation of cognition in lions and further supports expanding cognitive research to lions. PMID:27311315

  4. Genetic Evidence for Contrasting Wetland and Savannah Habitat Specializations in Different Populations of Lions (Panthera leo).

    PubMed

    Moore, Andy E; Cotterill, Fenton P D Woody; Winterbach, Christiaan W; Winterbach, Hanlie E K; Antunes, Agostinho; O'Brien, Stephen J

    2016-03-01

    South-central Africa is characterized by an archipelago of wetlands, which has evolved in time and space since at least the Miocene, providing refugia for animal species during Pleistocene arid episodes. Their importance for biodiversity in the region is reflected in the evolution of a variety of specialist mammal and bird species, adapted to exploit these wetland habitats. Populations of lions (Panthera leo) across south-central and east Africa have contrasting signatures of mitochondrial DNA haplotypes and biparental nuclear DNA in wetland and savannah habitats, respectively, pointing to the evolution of distinct habitat preferences. This explains the absence of genetic admixture of populations from the Kalahari savannah of southwest Botswana and the Okavango wetland of northern Botswana, despite separation by only 500 km. We postulate that ancestral lions were wetland specialists and that the savannah lions evolved from populations that were isolated during arid Pleistocene episodes. Expansion of grasslands and the resultant increase in herbivore populations during mesic Pleistocene climatic episodes provided the stimulus for the rapid population expansion and diversification of the highly successful savannah lion specialists. Our model has important implications for lion conservation. PMID:26695079

  5. Evaluation of microsatellite markers for populations studies and forensic identification of African lions (Panthera leo).

    PubMed

    Miller, Susan M; Harper, Cindy K; Bloomer, Paulette; Hofmeyr, Jennifer; Funston, Paul J

    2014-01-01

    The South African lion (Panthera leo) population is highly fragmented. One-third of its wild lions occur in small (<1000 km(2)) reserves. These lions were reintroduced from other areas of the species' historical range. Management practices on these reserves have not prioritized genetic provenance or heterozygosity. These trends potentially constrain the conservation value of these lions. To ensure the best management and long-term survival of these subpopulations as a viable collective population, the provenance and current genetic diversity must be described. Concurrently, poaching of lions to supply a growing market for lion bones in Asia may become a serious conservation challenge in the future. Having a standardized, validated method for matching confiscated lion parts with carcasses will be a key tool in investigating these crimes. We evaluated 28 microsatellites in the African lion using samples from 18 small reserves and 1 captive facility in South Africa, two conservancies in Zimbabwe, and Kruger National and Kgalagadi Transfrontier Parks to determine the loci most suited for population management and forensic genetic applications. Twelve microsatellite loci with a match probability of 1.1×10(-5) between siblings were identified for forensics. A further 10 could be added for population genetics studies. PMID:25151647

  6. Analysing Global Achievements in Orbital Lifetime Reduction at the End of LEO Missions

    NASA Astrophysics Data System (ADS)

    Krag, Holger; Lemmens, Stijn; Flohrer, Tim; Klinkard, Heiner

    2013-08-01

    The major driver for future debris proliferation, besides the intentional and unintentional release of objects, is the abundance of objects with large masses and sizes in orbit that could be involved in catastrophic collisions. Mitigation measures thus concentrate on the prevention of object release (explosions, mission-related objects, SRM (Solid Rocket Motor) exhaust products), the disposal of objects and active collision avoidance. As ESA's simulations show, the most effective means of stabilizing the space debris environment is the removal of mass from regions with high spatial densities. A limitation of the residence time of controlled objects in altitudes below 2000km to 25 years followed by either atmospheric re-entry or reboost to higher altitudes allows to limit the growth of object numbers in the densely populated LEO environment. This is the most relevant requirement for operations. In this paper we look into the achievements of all spacefaring nations with respect to this requirement. For this purpose, ESA has developed a method to determine the operational status of running missions, by monitoring their manoeuvre activity with the help of the publicly available orbit data distributed by the US Strategic Command (USSTRATCOM). Missions that have been found to have terminated their operational life will be processed to determine the remaining orbital lifetime. The results will be presented in a statistical manner.

  7. LEO Download Capacity Analysis for a Network of Adaptive Array Ground Stations

    NASA Technical Reports Server (NTRS)

    Ingram, Mary Ann; Barott, William C.; Popovic, Zoya; Rondineau, Sebastien; Langley, John; Romanofsky, Robert; Lee, Richard Q.; Miranda, Felix; Steffes, Paul; Mandl, Dan

    2005-01-01

    To lower costs and reduce latency, a network of adaptive array ground stations, distributed across the United States, is considered for the downlink of a polar-orbiting low earth orbiting (LEO) satellite. Assuming the X-band 105 Mbps transmitter of NASA s Earth Observing 1 (EO-1) satellite with a simple line-of-sight propagation model, the average daily download capacity in bits for a network of adaptive array ground stations is compared to that of a single 11 m dish in Poker Flats, Alaska. Each adaptive array ground station is assumed to have multiple steerable antennas, either mechanically steered dishes or phased arrays that are mechanically steered in azimuth and electronically steered in elevation. Phased array technologies that are being developed for this application are the space-fed lens (SFL) and the reflectarray. Optimization of the different boresight directions of the phased arrays within a ground station is shown to significantly increase capacity; for example, this optimization quadruples the capacity for a ground station with eight SFLs. Several networks comprising only two to three ground stations are shown to meet or exceed the capacity of the big dish, Cutting the data rate by half, which saves modem costs and increases the coverage area of each ground station, is shown to increase the average daily capacity of the network for some configurations.

  8. Head rubbing and licking reinforce social bonds in a group of captive African lions, Panthera leo.

    PubMed

    Matoba, Tomoyuki; Kutsukake, Nobuyuki; Hasegawa, Toshikazu

    2013-01-01

    Many social animals have a species-specific repertoire of affiliative behaviours that characterise individualised relationships within a group. To date, however, quantitative studies on intragroup affiliative behaviours in social carnivores have been limited. Here, we investigated the social functions of the two most commonly observed affiliative behaviours in captive African lions (Panthera leo): head rubbing and licking. We conducted behavioural observations on a captive group of lions composed of 7 males and 14 females, and tested hypotheses regarding three social functions: tension reduction, social bonding, and social status expression. Disproportionately frequent male-male and female-to-male head rubbing was observed, while more than 95% of all licking interactions occurred in female-female dyads. In accordance with the social bond hypothesis, and in disagreement with the social status expression hypothesis, both head rubbing and licking interactions were reciprocal. After controlling for spatial association, the dyadic frequency of head rubbing was negatively correlated with age difference while licking was positively correlated with relatedness. Group reunion after daily separation did not affect the frequencies of the affiliative behaviours, which was in disagreement with the predictions from the tension reduction hypothesis. These results support the social bond hypothesis for the functions of head rubbing and licking. Different patterns of affiliative behaviour between the sexes may reflect differences in the relationship quality in each sex or the differential predisposition to licking due to its original function in offspring care.

  9. Home range utilisation and territorial behaviour of lions (Panthera leo) on Karongwe Game Reserve, South Africa.

    PubMed

    Lehmann, Monika B; Funston, Paul J; Owen, Cailey R; Slotow, Rob

    2008-01-01

    Interventionist conservation management of territorial large carnivores has increased in recent years, especially in South Africa. Understanding of spatial ecology is an important component of predator conservation and management. Spatial patterns are influenced by many, often interacting, factors making elucidation of key drivers difficult. We had the opportunity to study a simplified system, a single pride of lions (Panthera leo) after reintroduction onto the 85 km(2) Karongwe Game Reserve, from 1999-2005, using radio-telemetry. In 2002 one male was removed from the paired coalition which had been present for the first three years. A second pride and male were in a fenced reserve adjacent of them to the east. This made it possible to separate social and resource factors in both a coalition and single male scenario, and the driving factors these seem to have on spatial ecology. Male ranging behaviour was not affected by coalition size, being driven more by resource rather than social factors. The females responded to the lions on the adjacent reserve by avoiding the area closest to them, therefore females may be more driven by social factors. Home range size and the resource response to water are important factors to consider when reintroducing lions to a small reserve, and it is hoped that these findings lead to other similar studies which will contribute to sound decisions regarding the management of lions on small reserves.

  10. Fiber type and metabolic characteristics of lion (Panthera leo), caracal (Caracal caracal) and human skeletal muscle.

    PubMed

    Kohn, Tertius Abraham; Burroughs, Richard; Hartman, Marthinus Jacobus; Noakes, Timothy David

    2011-06-01

    Lion (Panthera leo) and caracal (Caracal caracal) skeletal muscle samples from Vastus lateralis, Longissimus dorsi and Gluteus medius were analyzed for fiber type and citrate synthase (CS; EC 2.3.3.1), 3-hydroxyacyl Co A dehydrogenase (3HAD; EC 1.1.1.35), phosphofructokinase-1 (PFK; EC 2.7.1.11), creatine kinase (CK; EC 2.7.3.2), phosphorylase (PHOS; EC 2.4.1.1) and lactate dehydrogenase (LDH; EC 1.1.1.27) activities and compared to human runners, the latter also serving as validation of methodology. Both felids had predominantly type IIx fibers (range 50-80%), whereas human muscle had more types I and IIa. Oxidative capacity of both felids (CS: 5-9 μmol/min/g ww and 3HAD: 1.4-2.6 μmol/min/g ww) was lower than humans, whereas the glycolytic capacity was elevated. LDH activity of caracal (346 ± 81) was higher than lion (227 ± 62 μmol/min/g ww), with human being the lowest (55 ± 17). CK and PHOS activities were also higher in caracal and lion compared to human, but PFK was lower in both felid species. The current data and past research are illustrated graphically showing a strong relationship between type II fibers and sprinting ability in various species. These data on caracal and lion muscles confirm their sprinting behavior.

  11. Do acoustic features of lion, Panthera leo, roars reflect sex and male condition?

    PubMed

    Pfefferle, Dana; West, Peyton M; Grinnell, Jon; Packer, Craig; Fischer, Julia

    2007-06-01

    Long distance calls function to regulate intergroup spacing, attract mating partners, and/or repel competitors. Therefore, they may not only provide information about the sex (if both sexes are calling) but also about the condition of the caller. This paper provides a description of the acoustic features of roars recorded from 18 male and 6 female lions (Panthera leo) living in the Serengeti National park, Tanzania. After analyzing whether these roars differ between the sexes, tests whether male roars may function as indicators of their fighting ability or condition were conducted. Therefore, call characteristics were tested for relation to anatomical features as size, mane color, or mane length. Call characteristics included acoustic parameters that previously had been implied as indicators of size and fighting ability, e.g., call length, fundamental frequency, and peak frequency. The analysis revealed differences in relation to sex, which were entirely explained by variation in body size. No evidence that acoustic variables were related to male condition was found, indicating that sexual selection might only be a weak force modulating the lion's roar. Instead, lion roars may have mainly been selected to effectively advertise territorial boundaries.

  12. Leo Eitinger MD: tribute to a Holocaust survivor, humane physician and friend of mankind.

    PubMed

    Chelouche, Tessa

    2014-04-01

    Born in Czechoslovakia, psychiatrist Leo Eitinger (1912-1996) became internationally recognized for research on his fellow concentration camp inmates. He graduated as an MD in 1937, but being Jewish was prohibited from practicing as a doctor. When the Nazis occupied the area he was forced to flee to Norway, where in 1940 he was again deprived of his right to practice medicine. In 1942 he was arrested and deported to Auschwitz. There, as a physician inmate, he was able to help and in many cases save his fellow prisoners, not only with his medical skills but by falsifying prisoners' documents and hiding them from their Nazi captors. One of his patients was Elie Wiesel. Eitinger survived the camps but was forced to join a "death march." After the war he resumed medical practice in Norway, specializing in psychiatry. With his personal experience and knowledge of the suffering of camp survivors, he dedicated his life to studying the psychological effects of traumatic stress in different groups. Eitinger's academic contributions were crucial in the development of this area of research--namely, the effects of excessive stress, laying the foundations for the definition of post-traumatic stress disorder and the post-concentration camp syndrome, thus facilitating recognition of the medical and psychological post-war conditions of the survivors and their resultant disability pensions. PMID:24834755

  13. In-Orbit Lifetime Prediction for LEO and HEO Based on Orbit Determination from TLE Data

    NASA Astrophysics Data System (ADS)

    Agueda, A.; Aivar, L.; Tirado, J.; Dolado, J. C.

    2013-08-01

    Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subjected to decay and re-entry into the atmosphere due mainly to the drag force. While being this process the best solution to avoid the proliferation of debris in space and ensure the sustainability of future space activities, it implies a threat to the population on ground. Thus, the prediction of the in-orbit lifetime of an object and the evaluation of the risk on population and ground assets constitutes a crucial task. This paper will concentrate on the first of these tasks. Unfortunately the lifetime of an object in space is remarkably difficult to predict. This is mainly due to the dependence of the atmospheric drag on a number of uncertain elements such as the density profile and its dependence on the solar activity, the atmospheric conditions, the mass and surface area of the object (very difficult to evaluate), its uncontrolled attitude, etc. In this paper we will present a method for the prediction of this lifetime based on publicly available Two-Line Elements (TLEs) from the American USSTRATCOM's Joint Space Operations Center (JSpOC). TLEs constitute an excellent source to access routinely orbital information for thousands of objects even though of their reduced and unpredictable accuracy. Additionally, the implementation of the method on a CNES's Java-based tool will be presented. This tool (OPERA) is executed routinely at CNES to predict the orbital lifetime of a whole catalogue of objects.

  14. Characterization of a Bioflocculant Produced by a Consortium of Halomonas sp. Okoh and Micrococcus sp. Leo

    PubMed Central

    Okaiyeto, Kunle; Nwodo, Uchechukwu U.; Mabinya, Leonard V.; Okoh, Anthony I.

    2013-01-01

    The physicochemical and flocculating properties of a bioflocculant produced by a bacterial consortium composed of Halomonas sp. Okoh and Micrococcus sp. Leo were investigated. The purified bioflocculant was cation and pH dependent, and optimally flocculated kaolin clay suspension at a dosage of 0.1 mg/mL. The flocculating activity of the bioflocculant was stimulated in the presence of Ca2+, Mn2+, Al3+ and had a wide pH range of 2–10, with the highest flocculating activity of 86% at pH 8. The bioflocculant was thermostable and retained more than 70% of its flocculating activity after being heated at 80 °C for 30 min. Thermogravimetric analyses revealed a partial thermal decomposition of the biofloculant at 400 °C. The infrared spectrum showed the presence of hydroxyl, carboxyl and amino moieties as functional groups. The bioflocculant produced by the bacterial consortium appears to hold promising alternative to inorganic and synthetic organic flocculants that are widely used in wastewater treatment. PMID:24135818

  15. Analysis of Static Spacecraft Floating Potential at Low Earth Orbit (LEO)

    NASA Technical Reports Server (NTRS)

    Herr, Joel L.; Hwang, K. S.; Wu, S. T.

    1995-01-01

    Spacecraft floating potential is the charge on the external surfaces of orbiting spacecraft relative to the space. Charging is caused by unequal negative and positive currents to spacecraft surfaces. The charging process continues until the accelerated particles can be collected rapidly enough to balance the currents at which point the spacecraft has reached its equilibrium or floating potential. In low inclination. Low Earth Orbit (LEO), the collection of positive ion and negative electrons. in a particular direction. are typically not equal. The level of charging required for equilibrium to be established is influenced by the characteristics of the ambient plasma environment. by the spacecraft motion, and by the geometry of the spacecraft. Using the kinetic theory, a statistical approach for studying the interaction is developed. The approach used to study the spacecraft floating potential depends on which phenomena are being applied. and on the properties of the plasma. especially the density and temperature. The results from kinetic theory derivation are applied to determine the charging level and the electric potential distribution at an infinite flat plate perpendicular to a streaming plasma using finite-difference scheme.

  16. Location and removal of deslorelin acetate implants in female African lions (Panthera leo).

    PubMed

    Moresco, Anneke; Dadone, Liza; Arble, Jason; Klaphake, Eric; Agnew, Dalen W

    2014-06-01

    Contraception is necessary to manage zoo animal populations and to be able to house animals in groups without producing additional unwanted offspring. In felids and canids, an association between exposure to progestins and the occurrence of endometrial and mammary gland pathology has been documented. Therefore, the Association of Zoos and Aquariums (AZA) Wildlife Contraceptive Center recommends the use of deslorelin acetate for long-term contraception in carnivores. Return to cyclicity after deslorelin treatment has been variable; some individuals show ovarian suppression for long periods after the expected end of the deslorelin efficacy. In an attempt to reduce the time to reversal, techniques to locate and remove previous implants are being developed. This report documents the successful implementation of high-frequency ultrasonography in lions (Panthera leo) to locate and direct surgical removal of multiple deslorelin implants placed at least 2 yr previously as well as the return of follicular activity in both females at 7 months post-removal of implants. PMID:25000706

  17. Aktiv De-Orbiting Onboard System from Leo of Upper Stages of Launchers

    NASA Astrophysics Data System (ADS)

    Trushlyakov, V.; Shalay, V.; Shatrov, J.; Jakovlev, M.; Kostantino, A.

    2009-03-01

    The active de-orbiting onboard system (VDOS) of upper separable parts (USP) stage of launchers from LEO into orbits of utilization with term of existence orbital lifetimes till 25 years is offered. ADOS it is based on use of power resources of not produced rests of liquid fuel onboard USP launchers with liquid propulsion module (LPM). Following systems enter in structure VDOS: the gas jet propulsion system consisting of a system of gasification, chambers of gas engines (GE), a control system. For gasification of the rests of liquid fuel the heat-carrier received in the autonomous gas generator is used. The gasification propellant components from each tank with temperature and the pressure determined by strength of the corresponding tank, move in chambers of the GE established on a top of a fuel compartment. After separation of a payload execute twist USP for preservation of its position in the space by activity of the GE. Ways of increase of a system effectiveness of gasification are offered by superposition on the entered heat-carrier of ultrasonic oscillations, and also introduction in gaseous fuel nanopowder of aluminum. The volume of adaptations of construction USP, connected with introduction VDOS does not exceed 5 % from weight of a dry construction.

  18. Ulysses Radio Occultation Observations of the lo Plasma Torus During the Jupiter Encounter.

    PubMed

    Bird, M K; Asmar, S W; Brenkle, J P; Edenhofer, P; Funke, O; Pätzold, M; Volland, H

    1992-09-11

    Radio signals from Ulysses were used to probe the lo plasma torus (IPT) shortly after the spacecraft's closest approach to Jupiter. The frequencies of the two downlinks at S-band (2.3 gigahertz) and X-band (8.4 gigahertz) were recorded, differenced, and integrated in order to derive the columnar electron density of the IPT. The measurements agree qualitatively with contemporary models of the IPT based on Voyager data, but significant differences are apparent as well. The overall level of the IPT electron density is approximately the same as the prediction, implying that the amount of gas (or plasma) injected from lo is similar to that observed during the Voyager era. On the other hand, the IPT seems to be less extended out of the centrifugal equator, implying a smaller plasma temperature than predicted.

  19. 100-LBF LO2/LCH4 - Reaction Control Engine Technology Development for Future Space Vehicles

    NASA Technical Reports Server (NTRS)

    Robinson, Philip J.; Veith, Eric M.; Hurlbert, Eric A.; Jimenez, Rafael; Smith, Timothy D.

    2008-01-01

    The National Aeronautics and Space Administration (NASA) has identified liquid oxygen (LO2)/liquid methane (LCH4) propulsion systems as promising options for some future space vehicles. NASA issued a contract to Aerojet to develop a 100-lbf (445 N) LO2/LCH4 Reaction Control Engine (RCE) aimed at reducing the risk of utilizing a cryogenic reaction control system (RCS) on a space vehicle. Aerojet utilized innovative design solutions to develop an RCE that can ignite reliably over a broad range of inlet temperatures, perform short minimum impulse bits (MIB) at small electrical pulse widths (EPW), and produce excellent specific impulse (Isp) across a range of engine mixture ratios (MR). These design innovations also provide a start transient with a benign MR, ensuring good thrust chamber compatibility and long life. In addition, this RCE can successfully operate at MRs associated with main engines, enabling the RCE to provide emergency backup propulsion to minimize vehicle propellant load and overall system mass.

  20. Sedimentation survey of Lago Loíza, Trujillo Alto, Puerto Rico, July 2009

    USGS Publications Warehouse

    Soler-López, Luis R.; Licha-Soler, N.A.

    2014-01-01

    Lago Loíza is a reservoir formed at the confluence of Río Gurabo and Río Grande de Loíza in the municipality of Trujillo Alto in central Puerto Rico, about 10 kilometers (km) north of the town of Caguas, about 9 km northwest of Gurabo, and about 3 km south of Trujillo Alto (fig. 1). The Carraizo Dam is owned and operated by the Puerto Rico Aqueduct and Sewer Authority (PRASA), and was constructed in 1953 as a water-supply reservoir for the San Juan Metropolitan area. The dam is a concrete gravity structure that is located in a shallow valley and has a gently sloping left abutment and steep right abutment. Non-overflow sections flank the spillway section. Waterways include an intake structure for the pumping station and power plant, sluiceways, a trash sluice, and a spillway. The reservoir was built to provide a storage capacity of 26.8 million cubic meters (Mm3) of water at the maximum pool elevation of 41.14 meters (m) above mean sea level (msl) for the Sergio Cuevas Filtration Plant that serves the San Juan metropolitan area. The reservoir has a drainage area of 538 square kilometers (km2) and receives an annual mean rainfall that ranges from 1,600 to 5,000 millimeters per year (mm/yr). The principal streams that drain into Lago Loíza are the Río Grande de Loíza, Río Gurabo, and Río Cañas. Two other rivers, the Río Bairoa and Río Cagüitas, discharge into the Río Grande de Loíza just before it enters the reservoir. The combined mean annual runoff of the Río Grande de Loíza and the Río Gurabo for the 1960–2009 period of record is 323 Mm3. Flow from these streams constitutes about 89 percent of the total mean annual inflow of 364 Mm3 to the reservoir (U.S. Geological Survey, 2009). Detailed information about Lago Loíza reservoir structures, historical sediment accumulation, and a dredge conducted in 1999 are available in Soler-López and Gómez-Gómez (2005). During July 8–15, 2009, the U.S. Geological Survey (USGS) Caribbean Water Science

  1. Combination of Vandetanib, Radiotherapy, and Irinotecan in the LoVo Human Colorectal Cancer Xenograft Model

    SciTech Connect

    Wachsberger, Phyllis; Burd, Randy; Ryan, Anderson; Daskalakis, Constantine; Dicker, Adam P.

    2009-11-01

    Purpose: The tumor growth kinetics of the human LoVo colorectal xenograft model was assessed in response to vandetanib, an orally available receptor tyrosine kinase inhibitor, radiotherapy (RT), or irinotecan (CPT-11), as single therapies and in combination. Methods and Materials: LoVo cells were injected subcutaneously into the right hind limb (5x10{sup 6} cells in 100muL phosphate-buffered saline) of athymic NCR NUM mice and tumors were grown to a volume of 200-300 mm{sup 3} before treatment. Vandetanib was administered at 50 mg/kg daily orally for 14 days starting on Day 1. RT was given as three fractions (3x3 Gy) on Days 1, 2, and 3. CPT-11 was given at 15 mg/kg intraperitoneally on Days 1 and 3. Tumor volumes were measured on a daily basis and calculated by measuring tumor diameters with digital calipers in two orthogonal dimensions. Results: All three single treatments (vandetanib, CPT-11, and radiation) significantly slowed LoVo colorectal tumor growth. Vandetanib significantly increased the antitumor effects of CPT-11 and radiation when given in combination with either of these treatments. These treatment combinations resulted in a slow tumor growth rate during the 2 weeks of vandetanib administration. The triple combination of vandetanib, CPT-11, and radiation produced the most marked improvement in response as observed by measurable shrinkage of tumors during the first week of treatment. Conclusions: The tumor growth delay kinetics observed in this study of the LoVo colorectal model suggest concurrent and sustained post-sequencing of vandetanib with cytotoxic therapy may be beneficial in tumors of this type.

  2. N3LO NN interaction adjusted to light nuclei in ab exitu approach

    NASA Astrophysics Data System (ADS)

    Shirokov, A. M.; Shin, I. J.; Kim, Y.; Sosonkina, M.; Maris, P.; Vary, J. P.

    2016-10-01

    We use phase-equivalent transformations to adjust off-shell properties of similarity renormalization group evolved chiral effective field theory NN interaction (Idaho N3LO) to fit selected binding energies and spectra of light nuclei in an ab exitu approach. We then test the transformed interaction on a set of additional observables in light nuclei to verify that it provides reasonable descriptions of these observables with an apparent reduced need for three- and many-nucleon interactions.

  3. Ultra-low-voltage CMOS-based current bleeding mixer with high LO-RF isolation.

    PubMed

    Tan, Gim Heng; Sidek, Roslina Mohd; Ramiah, Harikrishnan; Chong, Wei Keat; Lioe, De Xing

    2014-01-01

    This journal presents an ultra-low-voltage current bleeding mixer with high LO-RF port-to-port isolation, implemented on 0.13 μm standard CMOS technology for ZigBee application. The architecture compliments a modified current bleeding topology, consisting of NMOS-based current bleeding transistor, PMOS-based switching stage, and integrated inductors achieving low-voltage operation and high LO-RF isolation. The mixer exhibits a conversion gain of 7.5 dB at the radio frequency (RF) of 2.4 GHz, an input third-order intercept point (IIP3) of 1 dBm, and a LO-RF isolation measured to 60 dB. The DC power consumption is 572 µW at supply voltage of 0.45 V, while consuming a chip area of 0.97 × 0.88 mm(2). PMID:25197694

  4. A Network Access Control Framework for 6LoWPAN Networks

    PubMed Central

    Oliveira, Luís M. L.; Rodrigues, Joel J. P. C.; de Sousa, Amaro F.; Lloret, Jaime

    2013-01-01

    Low power over wireless personal area networks (LoWPAN), in particular wireless sensor networks, represent an emerging technology with high potential to be employed in critical situations like security surveillance, battlefields, smart-grids, and in e-health applications. The support of security services in LoWPAN is considered a challenge. First, this type of networks is usually deployed in unattended environments, making them vulnerable to security attacks. Second, the constraints inherent to LoWPAN, such as scarce resources and limited battery capacity, impose a careful planning on how and where the security services should be deployed. Besides protecting the network from some well-known threats, it is important that security mechanisms be able to withstand attacks that have not been identified before. One way of reaching this goal is to control, at the network access level, which nodes can be attached to the network and to enforce their security compliance. This paper presents a network access security framework that can be used to control the nodes that have access to the network, based on administrative approval, and to enforce security compliance to the authorized nodes. PMID:23334610

  5. Effects of ADMA on gene expression and metabolism in serum-starved LoVo cells.

    PubMed

    Zheng, Ningning; Wang, Ke; He, Jiaojiao; Qiu, Yunping; Xie, Guoxiang; Su, Mingming; Jia, Wei; Li, Houkai

    2016-05-16

    Serum starvation is a typical way for inducing tumor cell apoptosis and stress. Asymmetric dimethylarginine (ADMA) is an endogenous metabolite. Our previous study reveals the plasma ADMA level is elevated in colon cancer patients, which can attenuate serum starvation-induced apoptosis in LoVo cells. In current study, we evaluated the effects of ADMA on gene expression and metabolism in serum-starved LoVo cells with gene microarray and metabolomic approaches. Our results indicated that 96 h serum starvation induced comprehensive alterations at transcriptional level, and most of them were restored by ADMA. The main signaling pathways induced by serum starvation included cancers-related pathways, pathways in cell death, apoptosis, and cell cycle etc. Meanwhile, the metabolomic data showed serum-starved cells were clearly separated with control cells, but not with ADMA-treated cells in PCA model. The identified differential metabolites indicated serum starvation significantly suppressed TCA cycle, altered glucose and fatty acids metabolism, as well as nucleic acids metabolism. However, very few differential metabolites were identified between ADMA and serum-starved cells. In summary, our current results indicated serum starvation profoundly altered the gene expression and metabolism of LoVo cells, whereas ADMA could restore most of the changes at transcriptional level, but not at metabolic level.

  6. Adenovirus KH901 promotes 5-FU antitumor efficacy and S phase in LoVo cells.

    PubMed

    Peng, Wei; Li, Jin; Yin, X G; Xu, J F; Cheng, L Z

    2012-06-01

    A combination of oncolytic and chemotherapeutic agents has been used to kill cancer cells. However, the effect of oncolytic adenoviruses on the cell cycle remains to be determined. Cytotoxicity assays were performed to determine cell death in cells treated with 5-fluorouracil (5-FU) alone or in combination with the oncolytic adenovirus KH901. Dynamic changes in the cell cycle, cell proliferation, and apoptosis-related proteins including p-AKT, Bcl-2, Bax, and caspase 3 were investigated after treatment with 5-FU with or without KH901. A higher proportion of S-phase cells were observed after treatment with KH901 and 5-FU than with 5-FU alone. p-AKT, Bcl-2, and Bax expression was increased upon treatment with KH901, whereas the expression of caspase-3 was not induced upon treatment with KH901 with or without 5-FU. KH901 exhibited significant potential as an oncolytic adenovirus and increased cell death in combination with 5-FU in LoVo cells, as compared to 5-FU alone. In conclusion, KH901 stimulates LoVo cells to enter the S-phase by activation of p-AKT, which could partly explain its synergistic effect with 5-FU on LoVo cell cytotoxicity.

  7. Fast Calcium Imaging with Optical Sectioning via HiLo Microscopy

    PubMed Central

    Sternberg, Jenna R.; Wyart, Claire; Emiliani, Valentina

    2015-01-01

    Imaging intracellular calcium concentration via reporters that change their fluorescence properties upon binding of calcium, referred to as calcium imaging, has revolutionized our way to probe neuronal activity non-invasively. To reach neurons densely located deep in the tissue, optical sectioning at high rate of acquisition is necessary but difficult to achieve in a cost effective manner. Here we implement an accessible solution relying on HiLo microscopy to provide robust optical sectioning with a high frame rate in vivo. We show that large calcium signals can be recorded from dense neuronal populations at high acquisition rates. We quantify the optical sectioning capabilities and demonstrate the benefits of HiLo microscopy compared to wide-field microscopy for calcium imaging and 3D reconstruction. We apply HiLo microscopy to functional calcium imaging at 100 frames per second deep in biological tissues. This approach enables us to discriminate neuronal activity of motor neurons from different depths in the spinal cord of zebrafish embryos. We observe distinct time courses of calcium signals in somata and axons. We show that our method enables to remove large fluctuations of the background fluorescence. All together our setup can be implemented to provide efficient optical sectioning in vivo at low cost on a wide range of existing microscopes. PMID:26625116

  8. Nature of the X(5568) — A critical Laplace sum rule analysis at N2LO

    NASA Astrophysics Data System (ADS)

    Albuquerque, R.; Narison, S.; Rabemananjara, A.; Rabetiarivony, D.

    2016-06-01

    We scrutinize recent QCD spectral sum rules (QSSR) results to lowest order (LO) predicting the masses of the BK molecule and (su)(bd¯) four-quark states. We improve these results by adding NLO and N2LO corrections to the PT contributions giving a more precise meaning on the b-quark mass definition used in the analysis. We extract our optimal predictions using Laplace sum rule (LSR) within the standard stability criteria versus the changes of the external free parameters (τ-sum rule variable, tc continuum threshold and subtraction constant μ). The smallness of the higher order PT corrections justifies (a posteriori) the LO order results ⊕ the uses of the ambiguous heavy quark mass to that order. However, our predicted spectra in the range (5173 ˜ 5226) MeV, summarized in Table 7, for exotic hadrons built with four different flavors (buds), do not support some previous interpretations of the D0 candidate,1 X(5568), as a pure molecule or a four-quark state. If experimentally confirmed, it could result from their mixing with an angle: sin 2𝜃 ≈ 0.15. One can also scan the region (2327 ˜ 2444) MeV (where the Ds0∗(2317) might be a good candidate) and the one (5173 ˜ 5226) MeV for detecting these (cuds) and (buds) unmixed exotic hadrons (if any) via, eventually, their radiative or π+hadrons decays.

  9. Nature of the X(5568) — A critical Laplace sum rule analysis at N2LO

    NASA Astrophysics Data System (ADS)

    Albuquerque, R.; Narison, S.; Rabemananjara, A.; Rabetiarivony, D.

    2016-06-01

    We scrutinize recent QCD spectral sum rules (QSSR) results to lowest order (LO) predicting the masses of the BK molecule and (su)(bd¯) four-quark states. We improve these results by adding NLO and N2LO corrections to the PT contributions giving a more precise meaning on the b-quark mass definition used in the analysis. We extract our optimal predictions using Laplace sum rule (LSR) within the standard stability criteria versus the changes of the external free parameters (τ-sum rule variable, tc continuum threshold and subtraction constant μ). The smallness of the higher order PT corrections justifies (a posteriori) the LO order results ⊕ the uses of the ambiguous heavy quark mass to that order. However, our predicted spectra in the range (5173 ˜ 5226) MeV, summarized in Table 7, for exotic hadrons built with four different flavors (buds), do not support some previous interpretations of the D0 candidate,1 X(5568), as a pure molecule or a four-quark state. If experimentally confirmed, it could result from their mixing with an angle: sin 2𝜃 ≈ 0.15. One can also scan the region (2327 ˜ 2444) MeV (where the Ds0∗(2317) might be a good candidate) and the one (5173 ˜ 5226) MeV for detecting these (cuds) and (buds) unmixed exotic hadrons (if any) via, eventually, their radiative or π+hadrons decays.

  10. Running of the contact interactions in chiral N3LO potentials from subtractive renormalization

    NASA Astrophysics Data System (ADS)

    Batista, E. F.; Szpigel, S.; Timóteo, V. S.

    2015-07-01

    In this work a subtracted kernel renormalization procedure (SKM) is applied to the chiral NN potential up to next-to-next-to-next-to-leading-order (N3 LO) to obtain the running of the renormalized contact strengths with the subtraction scale μ and the phase shifts for all uncoupled waves with contact interaction (S,P,D). We use two potentials constructed within the framework of Weinberg's approach to ChEFT, which provide a very accurate description of NN scattering data below laboratory energies E ∼ 350 MeV, namely Epelbaum, Glöckle and Meissner (N3LO-EGM) and Entem and Machleidt (N3LO-EM). For both potentials, we consider a large cutoff (30 fm-1) and analyze the phases and the running of the contact strengths with the subtraction point μ by making a fit of the K-matrix with five subtractions to the K-matrix from the Nijmegen II potential at low energies (E ≤ 20 MeV).

  11. Magnesium homeostasis in colon carcinoma LoVo cells sensitive or resistant to doxorubicin.

    PubMed

    Castiglioni, Sara; Cazzaniga, Alessandra; Trapani, Valentina; Cappadone, Concettina; Farruggia, Giovanna; Merolle, Lucia; Wolf, Federica I; Iotti, Stefano; Maier, Jeanette A M

    2015-11-13

    Neoplastic cells accumulate magnesium, an event which provides selective advantages and is frequently associated with TRPM7 overexpression. Little is known about magnesium homeostasis in drug-resistant cancer cells. Therefore, we used the colon cancer LoVo cell model and compared doxorubicin-resistant to sensitive cells. In resistant cells the concentration of total magnesium is higher while its influx capacity is lower than in sensitive cells. Accordingly, resistant cells express lower amounts of the TRPM6 and 7, both involved in magnesium transport. While decreased TRPM6 levels are due to transcriptional regulation, post-transcriptional events are involved in reducing the amounts of TRPM7. Indeed, the calpain inhibitor calpeptin markedly increases the levels of TRPM7 in resistant cells. In doxorubicin-sensitive cells, silencing TRPM7 shifts the phenotype to one more similar to resistant cells, since in these cells silencing TRPM7 significantly decreases the influx of magnesium, increases its intracellular concentration and increases resistance to doxorubicin. On the other hand, calpain inhibition upregulates TRPM7, decreases intracellular magnesium and enhances the sensitivity to doxorubicin of resistant LoVo cells. We conclude that in LoVo cells drug resistance is associated with alteration of magnesium homeostasis through modulation of TRPM7. Our data suggest that TRPM7 expression may be an additional undisclosed player in chemoresistance.

  12. Effects of ADMA on gene expression and metabolism in serum-starved LoVo cells

    PubMed Central

    Zheng, Ningning; Wang, Ke; He, Jiaojiao; Qiu, Yunping; Xie, Guoxiang; Su, Mingming; Jia, Wei; Li, Houkai

    2016-01-01

    Serum starvation is a typical way for inducing tumor cell apoptosis and stress. Asymmetric dimethylarginine (ADMA) is an endogenous metabolite. Our previous study reveals the plasma ADMA level is elevated in colon cancer patients, which can attenuate serum starvation-induced apoptosis in LoVo cells. In current study, we evaluated the effects of ADMA on gene expression and metabolism in serum-starved LoVo cells with gene microarray and metabolomic approaches. Our results indicated that 96 h serum starvation induced comprehensive alterations at transcriptional level, and most of them were restored by ADMA. The main signaling pathways induced by serum starvation included cancers-related pathways, pathways in cell death, apoptosis, and cell cycle etc. Meanwhile, the metabolomic data showed serum-starved cells were clearly separated with control cells, but not with ADMA-treated cells in PCA model. The identified differential metabolites indicated serum starvation significantly suppressed TCA cycle, altered glucose and fatty acids metabolism, as well as nucleic acids metabolism. However, very few differential metabolites were identified between ADMA and serum-starved cells. In summary, our current results indicated serum starvation profoundly altered the gene expression and metabolism of LoVo cells, whereas ADMA could restore most of the changes at transcriptional level, but not at metabolic level. PMID:27180883

  13. Ultra-Low-Voltage CMOS-Based Current Bleeding Mixer with High LO-RF Isolation

    PubMed Central

    Tan, Gim Heng; Sidek, Roslina Mohd; Chong, Wei Keat; Lioe, De Xing

    2014-01-01

    This journal presents an ultra-low-voltage current bleeding mixer with high LO-RF port-to-port isolation, implemented on 0.13 μm standard CMOS technology for ZigBee application. The architecture compliments a modified current bleeding topology, consisting of NMOS-based current bleeding transistor, PMOS-based switching stage, and integrated inductors achieving low-voltage operation and high LO-RF isolation. The mixer exhibits a conversion gain of 7.5 dB at the radio frequency (RF) of 2.4 GHz, an input third-order intercept point (IIP3) of 1 dBm, and a LO-RF isolation measured to 60 dB. The DC power consumption is 572 µW at supply voltage of 0.45 V, while consuming a chip area of 0.97 × 0.88 mm2. PMID:25197694

  14. Magnesium homeostasis in colon carcinoma LoVo cells sensitive or resistant to doxorubicin

    PubMed Central

    Castiglioni, Sara; Cazzaniga, Alessandra; Trapani, Valentina; Cappadone, Concettina; Farruggia, Giovanna; Merolle, Lucia; Wolf, Federica I.; Iotti, Stefano; Maier, Jeanette A M

    2015-01-01

    Neoplastic cells accumulate magnesium, an event which provides selective advantages and is frequently associated with TRPM7overexpression. Little is known about magnesium homeostasis in drug-resistant cancer cells. Therefore, we used the colon cancer LoVo cell model and compared doxorubicin-resistant to sensitive cells. In resistant cells the concentration of total magnesium is higher while its influx capacity is lower than in sensitive cells. Accordingly, resistant cells express lower amounts of the TRPM6 and 7, both involved in magnesium transport. While decreased TRPM6 levels are due to transcriptional regulation, post-transcriptional events are involved in reducing the amounts of TRPM7. Indeed, the calpain inhibitor calpeptin markedly increases the levels of TRPM7 in resistant cells. In doxorubicin-sensitive cells, silencing TRPM7 shifts the phenotype to one more similar to resistant cells, since in these cells silencing TRPM7 significantly decreases the influx of magnesium, increases its intracellular concentration and increases resistance to doxorubicin. On the other hand, calpain inhibition upregulates TRPM7, decreases intracellular magnesium and enhances the sensitivity to doxorubicin of resistant LoVo cells. We conclude that in LoVo cells drug resistance is associated with alteration of magnesium homeostasis through modulation of TRPM7. Our data suggest that TRPM7 expression may be an additional undisclosed player in chemoresistance. PMID:26563869

  15. PI3K/Akt pathway involving into apoptosis and invasion in human colon cancer cells LoVo.

    PubMed

    Jiang, Qun Guang; Li, Tai Yuan; Liu, Dong Ning; Zhang, Hai Tao

    2014-05-01

    In this study we determined the effects of Curcumin on human colon cancer cells line LoVo. We found that Curcumin significantly inhibited the proliferation, migration and invasion, and clone formation of LoVo cells in a dose-dependent manner. Curcumin also dose-dependently reduced the phosphorylation of proteins Akt and increased expression levels of the genes caspase-3, cytochrome-c, Bax mRNA in LoVo cells. In addition, Curcumin dose-dependently decreased gene Bcl-2 mRNA expression. Similar results were observed in LoVo cells treated with LY294002. These in vitro studies suggest that Curcumin may play its anti-cancer actions partly via suppressing PI3K/Akt signal pathway in LoVo cells.

  16. Operational Impact of Improved Space Tracking on Collision Avoidance in the Future LEO Space Debris Environment

    NASA Astrophysics Data System (ADS)

    Sibert, D.; Borgeson, D.; Peterson, G.; Jenkin, A.; Sorge, M.

    2010-09-01

    Even if global space policy successfully curtails on orbit explosions and ASAT demonstrations, studies indicate that the number of debris objects in Low Earth Orbit (LEO) will continue to grow solely from debris on debris collisions and debris generated from new launches. This study examines the threat posed by this growing space debris population over the next 30 years and how improvements in our space tracking capabilities can reduce the number of Collision Avoidance (COLA) maneuvers required keep the risk of operational satellite loss within tolerable limits. Particular focus is given to satellites operated by the Department of Defense (DoD) and Intelligence Community (IC) in Low Earth Orbit (LEO). The following debris field and space tracking performance parameters were varied parametrically in the experiment to study the impact on the number of collision avoidance maneuvers required: - Debris Field Density (by year 2009, 2019, 2029, and 2039) - Quality of Track Update (starting 1 sigma error ellipsoid) - Future Propagator Accuracy (error ellipsoid growth rates - Special Perturbations in 3 axes) - Track Update Rate for Debris (stochastic) - Track Update Rate for Payloads (stochastic) Baseline values matching present day tracking performance for quality of track update, propagator accuracy, and track update rate were derived by analyzing updates to the unclassified Satellite Catalog (SatCat). Track update rates varied significantly for active payloads and debris and as such we used different models for the track update rates for military payloads and debris. The analysis was conducted using the System Effectiveness Analysis Simulation (SEAS) an agent based model developed by the United States Air Force Space Command’s Space and Missile Systems Center to evaluate the military utility of space systems. The future debris field was modeled by The Aerospace Corporation using a tool chain which models the growth of the 10cm+ debris field using high fidelity

  17. Addressing challenges in combining GOES and LEO satellite products of the CONUS

    NASA Astrophysics Data System (ADS)

    Petersen, R. A.; Dworak, R.

    2012-12-01

    The challenges of transforming data from the next generation of satellites into information and products for the weather and science purposes presents a major challenge to both the research and applications communities. This will be especially difficult over land, where the process of integrating observations from multiple instruments and platforms in real time is complicated by the influence of the land surface on the observations themselves. In addition, effective merging of the mixture of time-continuous GEO and less frequent but higher spectral resolution LEO observations with other new surface-based observations will be essential and require new product processing strategies. The material shown in this presentation will begin to address some of these issues. It will describe results of efforts to inter-calibrate moisture products derived from existing GEO and LEO data sets over land designed 1) to identify and remove biases from the GOES moisture retrievals, 2) to determine the seasonally varying information content of the GOES relative to NWP model 'first guess' fields, 3) to determine the similarities and differences in error structures between GOES and AIRS retrievals, and 4) to determine the vertical structure of the errors in both systems. For example, comparisons have been made between GOES Total Precipitable Water (TPW) using the Li retrieval system (GOES-Li) and data from Raman Lidar (RL), Microwave Radiometer (MWR) and surface-based GPS-Met systems at the ARM CART site. The test showed for using one year of derived TPW products, the NWP model first guess (GFS) and GOES-Li products are wetter, however the GOES-Li beats the GFS in the warm season, especially in August when the NWP precipitation skill is least. During the warm season GOES-Li is noticeably better than GFS (which was too wet) during daytime. In addition, the GPS-Met data are best during the daytime, while the Ramon Lidar performs best at night. AIRS products were also evaluated for several

  18. Mycobacterium bovis infection in the lion (Panthera leo): Current knowledge, conundrums and research challenges.

    PubMed

    Viljoen, Ignatius M; van Helden, Paul D; Millar, Robert P

    2015-06-12

    Mycobacterium bovis has global public-health and socio-economic significance and can infect a wide range of species including the lion (Panthera leo) resulting in tuberculosis. Lions are classified as vulnerable under the IUCN Red List of Threatened Species and have experienced a 30% population decline in the past two decades. However, no attempt has been made to collate and critically evaluate the available knowledge of M. bovis infections in lions and potential effects on population. In this review we set out to redress this. Arguments suggesting that ingestion of infected prey animals are the main route of infection for lions have not been scientifically proven and research is needed into other possible sources and routes of infection. The paucity of knowledge on host susceptibility, transmission directions and therefore host status, manifestation of pathology, and epidemiology of the disease in lions also needs to be addressed. Advances have been made in diagnosing the presence of M. bovis in lions. However, these diagnostic tests are unable to differentiate between exposure, presence of infection, or stage of disease. Furthermore, there are contradictory reports on the effects of M. bovis on lion populations with more data needed on disease dynamics versus the lion population's reproductive dynamics. Knowledge on disease effects on the lion reproduction and how additional stressors such as drought or co-morbidities may interact with tuberculosis is also lacking. Filling these knowledge gaps will contribute to the understanding of mycobacterial infections and disease in captive and wild lions and assist in lion conservation endeavours. PMID:25891424

  19. Neurologic Disease in Captive Lions (Panthera leo) with Low-Titer Lion Lentivirus Infection▿

    PubMed Central

    Brennan, Greg; Podell, Michael D.; Wack, Raymund; Kraft, Susan; Troyer, Jennifer L.; Bielefeldt-Ohmann, Helle; VandeWoude, Sue

    2006-01-01

    Lion lentivirus (LLV; also known as feline immunodeficiency virus of lion, Panthera leo [FIVPle]) is present in free-ranging and captive lion populations at a seroprevalence of up to 100%; however, clinical signs are rarely reported. LLV displays up to 25% interclade sequence diversity, suggesting that it has been in the lion population for some time and may be significantly host adapted. Three captive lions diagnosed with LLV infection displayed lymphocyte subset alterations and progressive behavioral, locomotor, and neuroanatomic abnormalities. No evidence of infection with other potential neuropathogens was found. Antemortem electrodiagnostics and radiologic imaging indicated a diagnosis consistent with lentiviral neuropathy. PCR was used to determine a partial lentiviral genomic sequence and to quantify the proviral burden in eight postmortem tissue specimens. Phylogenetic analysis demonstrated that the virus was consistent with the LLV detected in other captive and free-ranging lions. Despite progressive neurologic signs, the proviral load in tissues, including several regions of the brain, was low; furthermore, gross and histopathologic changes in the brain were minimal. These findings suggest that the symptoms in these animals resulted from nonspecific encephalopathy, similar to human immunodeficiency virus, FIV, and simian immunodeficiency virus (SIV) neuropathies, rather than a direct effect of active viral replication. The association of neuropathy and lymphocyte subset alterations with chronic LLV infection suggests that long-term LLV infection can have detrimental effects for the host, including death. This is similar to reports of aged sootey mangabeys dying from diseases typically associated with end-stage SIV infection and indicates areas for further research of lentiviral infections of seemingly adapted natural hosts, including mechanisms of host control and viral adaptation. PMID:17005739

  20. Application of the NASCAP Spacecraft Simulation Tool to Investigate Electrodynamic Tether Current Collection in LEO

    NASA Technical Reports Server (NTRS)

    Adams, Mitzi; HabashKrause, Linda

    2012-01-01

    Recent interest in using electrodynamic tethers (EDTs) for orbital maneuvering in Low Earth Orbit (LEO) has prompted the development of the Marshall ElectroDynamic Tether Orbit Propagator (MEDTOP) model. The model is comprised of several modules which address various aspects of EDT propulsion, including calculation of state vectors using a standard orbit propagator (e.g., J2), an atmospheric drag model, realistic ionospheric and magnetic field models, space weather effects, and tether librations. The natural electromotive force (EMF) attained during a radially-aligned conductive tether results in electrons flowing down the tether and accumulating on the lower-altitude spacecraft. The energy that drives this EMF is sourced from the orbital energy of the system; thus, EDTs are often proposed as de-orbiting systems. However, when the current is reversed using satellite charged particle sources, then propulsion is possible. One of the most difficult challenges of the modeling effort is to ascertain the equivalent circuit between the spacecraft and the ionospheric plasma. The present study investigates the use of the NASA Charging Analyzer Program (NASCAP) to calculate currents to and from the tethered satellites and the ionospheric plasma. NASCAP is a sophisticated set of computational tools to model the surface charging of three-dimensional (3D) spacecraft surfaces in a time-varying space environment. The model's surface is tessellated into a collection of facets, and NASCAP calculates currents and potentials for each one. Additionally, NASCAP provides for the construction of one or more nested grids to calculate space potential and time-varying electric fields. This provides for the capability to track individual particles orbits, to model charged particle wakes, and to incorporate external charged particle sources. With this study, we have developed a model of calculating currents incident onto an electrodynamic tethered satellite system, and first results are shown

  1. The evolutionary dynamics of the lion Panthera leo revealed by host and viral population genomics.

    PubMed

    Antunes, Agostinho; Troyer, Jennifer L; Roelke, Melody E; Pecon-Slattery, Jill; Packer, Craig; Winterbach, Christiaan; Winterbach, Hanlie; Hemson, Graham; Frank, Laurence; Stander, Philip; Siefert, Ludwig; Driciru, Margaret; Funston, Paul J; Alexander, Kathy A; Prager, Katherine C; Mills, Gus; Wildt, David; Bush, Mitch; O'Brien, Stephen J; Johnson, Warren E

    2008-11-01

    The lion Panthera leo is one of the world's most charismatic carnivores and is one of Africa's key predators. Here, we used a large dataset from 357 lions comprehending 1.13 megabases of sequence data and genotypes from 22 microsatellite loci to characterize its recent evolutionary history. Patterns of molecular genetic variation in multiple maternal (mtDNA), paternal (Y-chromosome), and biparental nuclear (nDNA) genetic markers were compared with patterns of sequence and subtype variation of the lion feline immunodeficiency virus (FIV(Ple)), a lentivirus analogous to human immunodeficiency virus (HIV). In spite of the ability of lions to disperse long distances, patterns of lion genetic diversity suggest substantial population subdivision (mtDNA Phi(ST) = 0.92; nDNA F(ST) = 0.18), and reduced gene flow, which, along with large differences in sero-prevalence of six distinct FIV(Ple) subtypes among lion populations, refute the hypothesis that African lions consist of a single panmictic population. Our results suggest that extant lion populations derive from several Pleistocene refugia in East and Southern Africa ( approximately 324,000-169,000 years ago), which expanded during the Late Pleistocene ( approximately 100,000 years ago) into Central and North Africa and into Asia. During the Pleistocene/Holocene transition ( approximately 14,000-7,000 years), another expansion occurred from southern refugia northwards towards East Africa, causing population interbreeding. In particular, lion and FIV(Ple) variation affirms that the large, well-studied lion population occupying the greater Serengeti Ecosystem is derived from three distinct populations that admixed recently.

  2. Comparative skull analysis suggests species-specific captivity-related malformation in lions (Panthera leo).

    PubMed

    Saragusty, Joseph; Shavit-Meyrav, Anat; Yamaguchi, Nobuyuki; Nadler, Rona; Bdolah-Abram, Tali; Gibeon, Laura; Hildebrandt, Thomas B; Shamir, Merav H

    2014-01-01

    Lion (Panthera leo) populations have dramatically decreased worldwide with a surviving population estimated at 32,000 across the African savannah. Lions have been kept in captivity for centuries and, although they reproduce well, high rates of stillbirths as well as morbidity and mortality of neonate and young lions are reported. Many of these cases are associated with bone malformations, including foramen magnum (FM) stenosis and thickened tentorium cerebelli. The precise causes of these malformations and whether they are unique to captive lions remain unclear. To test whether captivity is associated with FM stenosis, we evaluated 575 lion skulls of wild (N = 512) and captive (N = 63) origin. Tiger skulls (N = 276; 56 captive, 220 wild) were measured for comparison. While no differences were found between males and females or between subadults and adults in FM height (FMH), FMH of captive lions (17.36±3.20 mm) was significantly smaller and with greater variability when compared to that in wild lions (19.77±2.11 mm). There was no difference between wild (18.47±1.26 mm) and captive (18.56±1.64 mm) tigers in FMH. Birth origin (wild vs. captive) as a factor for FMH remained significant in lions even after controlling for age and sex. Whereas only 20/473 wild lions (4.2%) had FMH equal to or smaller than the 5th percentile of the wild population (16.60 mm), this was evident in 40.4% (23/57) of captive lion skulls. Similar comparison for tigers found no differences between the captive and wild populations. Lions with FMH equal to or smaller than the 5th percentile had wider skulls with smaller cranial volume. Cranial volume remained smaller in both male and female captive lions when controlled for skull size. These findings suggest species- and captivity-related predisposition for the pathology in lions.

  3. Multiwavelength Optical Observations of Two Chromospherically Active Binary Systems: V789 Mon and GZ Leo

    NASA Astrophysics Data System (ADS)

    Gálvez, M. C.; Montes, D.; Fernández-Figueroa, M. J.; De Castro, E.; Cornide, M.

    2009-04-01

    This paper describes a multiwavelength optical study of chromospheres in two X-ray/EUV-selected active binary stars with strong Hα emission, V789 Mon (2RE J0725 - 002) and GZ Leo (2RE J1101+223). The goal of the study is to determine radial velocities and fundamental stellar parameters in chromospherically active binary systems in order to include them in the activity-rotation and activity-age relations. We carried out high-resolution echelle spectroscopic observations and applied spectral-subtraction technique in order to measure emission excesses due to chromosphere. The detailed study of activity indicators allowed us to characterize the presence of different chromospheric features in these systems and enabled to include them in a larger activity-rotation survey. We computed radial velocities of the systems using cross-correlation with the radial velocity standards. The double-line spectral binarity was confirmed and the orbital solutions improved for both systems. In addition, other stellar parameters such as spectral types, projected rotational velocities (vsin i) and the equivalent width of the lithium Li I λ6707.8 Å absorption line were determined. Based on observations collected with the 2.2 m telescope at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto (Almería, Spain), operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC) and with the 2.1 m Otto Struve Telescope at McDonald Observatory of the University of Texas at Austin (USA).

  4. LEO spacecraft leakage current and discharging phenomena - TRW LDEF SP-HVDE (space plasma-high voltage drainage experiment)

    NASA Technical Reports Server (NTRS)

    Yaung, J. Y.; Wong, W. C.; Blakkolb, B. K.; Ryan, L. E.; Taylor, W. W. L.

    1991-01-01

    Two identical SP-HVDE trays were flown in the NASA 5.75-year LDEF (Long Duration Exposure Facility), one near the leading edge and the other near the trailing edge, in the LEO (low earth orbit) environment. Each experiment tray consisted of six assemblies with each made of Kapton dielectric samples of varying thicknesses (i.e., 2 mils, 3 mils, and 5 mils) biased under +/- 300 V, +/- 500 V, and +/- 1000 V. The objectives have been successfully achieved by measuring the first post-flight long-term (i.e. roughly 8-month experiment) average leakage current through 95 percent measurable coulombmeters and surface materials.

  5. G-LoSA: An efficient computational tool for local structure-centric biological studies and drug design.

    PubMed

    Lee, Hui Sun; Im, Wonpil

    2016-04-01

    Molecular recognition by protein mostly occurs in a local region on the protein surface. Thus, an efficient computational method for accurate characterization of protein local structural conservation is necessary to better understand biology and drug design. We present a novel local structure alignment tool, G-LoSA. G-LoSA aligns protein local structures in a sequence order independent way and provides a GA-score, a chemical feature-based and size-independent structure similarity score. Our benchmark validation shows the robust performance of G-LoSA to the local structures of diverse sizes and characteristics, demonstrating its universal applicability to local structure-centric comparative biology studies. In particular, G-LoSA is highly effective in detecting conserved local regions on the entire surface of a given protein. In addition, the applications of G-LoSA to identifying template ligands and predicting ligand and protein binding sites illustrate its strong potential for computer-aided drug design. We hope that G-LoSA can be a useful computational method for exploring interesting biological problems through large-scale comparison of protein local structures and facilitating drug discovery research and development. G-LoSA is freely available to academic users at http://im.compbio.ku.edu/GLoSA/. PMID:26813336

  6. Higgs boson gluon-fusion production beyond threshold in N3LO QCD

    SciTech Connect

    Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard

    2015-03-18

    In this study, we compute the gluon fusion Higgs boson cross-section at N3LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N3LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N3LO in perturbative QCD.

  7. Resonant behaviour of GaAs LO phonons in a GaAs-AlAs superlattice

    NASA Astrophysics Data System (ADS)

    Zhang, Shulin; T, A. Gant; M, Delaney; M, V. Klein; J, Klem; H, Morkoc

    1988-03-01

    Resonant Raman scattering from GaAs LO phonons in a 59Å GaAs/20Å AlAs superlattice was studied. The relevant intersubband energies were determined. The results suggest that all of the exciton transitions from the hole subbands HH1, LH1, HH2, HH3, LH2 and HH4 to the electron subbands CB1 and CB2 in the energy region covered by our incident dye laser were observed and a justificative analysis may involve effects due to valence band mixing and to 3D electronic miniband structure.

  8. Consistent Ocean Mass Time Series from LEO Potential Field Missions (CONTIM)

    NASA Astrophysics Data System (ADS)

    Lück, Christina; Ren, Le; Androsov, Alexey; Kusche, Jürgen; Schröter, Jens; Danilov, Sergey; Rietbroek, Roelof

    2016-04-01

    Ocean mass variability on timescales of months to decades is still insufficiently understood. On these timescales, large-scale ocean bottom pressure (OBP) anomalies are associated both with wind induced variability as well as baroclinic processes, i.e. related to vertical shear of ocean density. The GRACE mission has been instrumental in quantifying such mass fluctuations, yet its lifetime is limited. The broader importance of non-tidal ocean mass variability for oceanography but also geodesy (i.e. for understanding the time-varying geoid, shape of the Earth's crust, centre of figure, Earth rotation) is obvious. Deep ocean processes can only be understood properly when not only sea surface height and upper ocean steric expansion are measured but deep ocean pressure anomalies are accounted for in addition. Apart from GRACE, the SWARM constellation may provide information on the lowest degrees of the time-variable gravity field of the Earth and therefore of large-scale oceanic processes. Here we introduce the project CONTIM, which is run in the framework of the German Special Priority Programme "Dynamic Earth" (SPP1788). In CONTIM we propose to combine expertise on precise satellite orbit determination, gravity field and mass modelling, and physical oceanography to retrieve, analyse and verify consistent time series of ocean mass variations from a set of low-flying Earth orbiters including GRACE, but extending the GRACE time series. This information is used to advance our understanding of oceanic movement, ocean warming and sea level rise. CONTIM will thus synergistically address three areas: (1) the methodology of precisely determining LEO orbits, applied here to the SWARM constellation. (2) a new method of retrieving large-scale time-varying gravity (TVG) and mass change associated with oceanic (and cryospheric and hydrological) processes from results of (1), based on forward modelling. (3) physical modelling of ocean mass variations, both for improved forward

  9. Major Design Drivers for LEO Space Surveillance in Europe and Solution Concepts

    NASA Astrophysics Data System (ADS)

    Krag, Holger; Flohrer, Tim; Klinkrad, Heiner

    Europe is preparing for the development of an autonomous system for space situational aware-ness. One important segment of this new system will be dedicated to surveillance and tracking of space objects in Earth orbits. First concept and capability analysis studies have led to a draft system proposal. This proposal foresees, in a first deployment step, a groundbased system consisting of radar sensors and a network of optical telescopes. These sensors will be designed to have the capability of building up and maintaining a catalogue of space objects. A number of related services will be provided, including collision avoidance and the prediction of uncontrolled reentry events. Currently, the user requirements are consolidated, defining the different services, and the related accuracy and timeliness of the derived products. In this consolidation process parameters like the lower diameter limit above which catalogue coverage is to be achieved, the degree of population coverage in various orbital regions and the accuracy of the orbit data maintained in the catalogue are important design drivers for the selection of number and location of the sensors, and the definition of the required sensor performance. Further, the required minimum time for the detection of a manoeuvre, a newly launched object or a fragmentation event, significantly determines the required surveillance performance. In the requirement consolidation process the performance to be specified has to be based on a careful analysis which takes into account accuracy constraints of the services to be provided, the technical feasibility, complexity and costs. User requirements can thus not be defined with-out understanding the consequences they would pose on the system design. This paper will outline the design definition process for the surveillance and tracking segment of the European space situational awareness system. The paper will focus on the low-Earth orbits (LEO). It will present the core user

  10. Novel low cost standardized Nano-Satellite structure bus for LEO missions

    NASA Astrophysics Data System (ADS)

    Anubhav, T.; Sarwesh, P.; Narayan, V.; Varma, P. A.; Prasad, R. A.; Loganathan, M.; Rao, D. N.; Sriram, S.; Venkatesh, M.

    This paper focuses on SRMSAT STRUCTURE BUS which is a standardized Nano-Satellite structure bus. It provides a standard platform for a wide variety of missions in LEO and can be realized in a very short developmental period. The bus was designed and developed for SRMSAT, the SRM University (Sri Ramaswamy Memorial University) student Nano-Satellite, by the undergraduate students and faculty of SRM University in collaboration with Indian Space Research Organization (ISRO). The bus can support payloads up to a mass of 20kg. SRMSAT STRUCTURE BUS has a mass of around 6 kg and dimensions 280mm × 280mm × 280mm with an available volume of 11000 cc. Vibration Testing of the bus has been performed upto 6.7 gRMS. This makes the satellite capable of being launched by any launch vehicle in the world. An innovative PCB mounting design has been introduced in this structure bus which facilitates mounting of a maximum 7 PCB trays independently, each tray capable of holding a 250 mm2 PCB. Structural analysis of SRMSAT STRUCTURE BUS was done using NX Nastran. The boundary conditions for each analysis were defined based on the loading conditions as specified by the launcher, PSLV (Polar Satellite Launch Vehicle). Optimization of each individual component was performed by maintaining a minimum threshold between the local frequencies of the component and global frequencies of the entire satellite. Static, Modal, Harmonic and Random Vibration analysis of the structure bus was performed. This paper also describes the methodology followed in the static and dynamic analysis of the structure bus to finalize the design. The results have been tested and validated at ISRO Satellite Centre, Bangalore with around 90% accuracy and the structure has been certified as a standard structure bus for Nano-satellite missions. In terms of expandability, this structure bus is capable of accommodating deployable solar panels. Also, the payload mounting is not only restricted to th- bottom deck but can

  11. LEO-to-ground polarization measurements aiming for space QKD using Small Optical TrAnsponder (SOTA).

    PubMed

    Carrasco-Casado, Alberto; Kunimori, Hiroo; Takenaka, Hideki; Kubo-Oka, Toshihiro; Akioka, Maki; Fuse, Tetsuharu; Koyama, Yoshisada; Kolev, Dimitar; Munemasa, Yasushi; Toyoshima, Morio

    2016-05-30

    Quantum communication, and more specifically Quantum Key Distribution (QKD), enables the transmission of information in a theoretically secure way, guaranteed by the laws of quantum physics. Although fiber-based QKD has been readily available since several years ago, a global quantum communication network will require the development of space links, which remains to be demonstrated. NICT launched a LEO satellite in 2014 carrying a lasercom terminal (SOTA), designed for in-orbit technological demonstrations. In this paper, we present the results of the campaign to measure the polarization characteristics of the SOTA laser sources after propagating from LEO to ground. The most-widely used property for encoding information in free-space QKD is the polarization, and especially the linear polarization. Therefore, studying its behavior in a realistic link is a fundamental step for proving the feasibility of space quantum communications. The results of the polarization preservation of two highly-polarized lasers are presented here, including the first-time measurement of a linearly-polarized source at λ = 976 nm and a circularly-polarized source at λ = 1549 nm from space using a realistic QKD-like receiver, installed in the Optical Ground Station at the NICT Headquarters, in Tokyo, Japan.

  12. Verification of the GSICS GEO-LEO inter-calibration products with GEO-GEO collocation data

    NASA Astrophysics Data System (ADS)

    Yu, Fangfang; Wu, Xiangqian; Qian, Haifeng; Sindic-Rancic, Gordana

    2011-10-01

    The Global Space-based Inter-Calibration System (GSICS) geostationary (GEO) vs. low earth orbit (LEO) inter-calibration correction products have been routinely generated for years at NOAA to improve and harmonize the data quality of the operational GOES satellite for a better global weather monitoring, prediction and climate change studies. In this study, the collocated GOES-13 and GOES-15 Imager infrared (IR) data are used to validate the GSICS GEO-LEO Imager inter-calibration correction products. To compensate the impact of difference in the spectral response function (SRF) on the GSICS corrected GEO radiance, two radiative transfer models (RTM) with different atmospheric profiles are used to simulate the relations between the two GEO radiance values. The results of GEO-GEO inter-calibration shows that the mean Tb difference between GOES-13 and GOES-15 is less than 0.2K(Ch2), 0.65K(Ch3), 0.08K(Ch4) and 0.35K(Ch6). The two RTM models with different atmospheric profiles have significantly different impacts on the Tb difference at the two absorptive channels, Ch3 and Ch6, indicating that the impact of different optical path is not well addressed in this study. Future study should apply the double difference using the RTM as transfer to compensate for the SRF and viewing/optical path difference at each collocated pixel.

  13. The impact of lift and drag on 6DOF motion of LEO objects : formation control and debris behaviour

    NASA Astrophysics Data System (ADS)

    Smith, Brenton; Boyce, Russell; Brown, Melrose

    2016-07-01

    Perturbing forces on spacecraft are a challenge for the establishment and maintenance of satellite formations. For large satellites, the use of thrusters is a practical means of countering perturbing forces. However, long-term thrusting is not currently feasible for miniaturised satellites due to volume and mass constraints. Astrodynamics effects - in particular, passive aerodynamic lift and drag forces - are possible means for miniaturised satellites to maintain a formation in Low Earth Orbit (LEO). Currently, lift and drag for rendezvous have been considered in the presence of simplified orbital models, namely two body motion with the J2 effect. Given the small magnitude of lift and drag in LEO, it is unclear as to the control effectiveness of these aerodynamic forces under all orbital perturbations including solar radiation pressure, third body gravitation, and the non-spherical gravity. The work presented here will explore the extent to which aerodynamic lift and drag can be utilised for formation establishment and maintenance under changing operating conditions, including altitude, orbital inclination, space weather, sensor errors, and all-encompassing orbital perturbations. This work applies an in-house developed orbital propagation code to simulate the motion of formation flying spacecraft under differing conditions. The results will help miniaturised satellite formation flight planners better plan and operate future formation missions, and will also feed into improved understanding of the 6DOF motion of near-Earth orbit objects, including that of uncontrolled objects such as space debris.

  14. Determining the Rotation Periods of an Inactive LEO Satellite and the First Korean Space Debris on GEO, KOREASAT 1

    NASA Astrophysics Data System (ADS)

    Choi, Jin; Jo, Jung Hyun; Kim, Myung-Jin; Roh, Dong-Goo; Park, Sun-Youp; Lee, Hee-Jae; Park, Maru; Choi, Young-Jun; Yim, Hong-Suh; Bae, Young-Ho; Park, Young-Sik; Cho, Sungki; Moon, Hong-Kyu; Choi, Eun-Jung; Jang, Hyun-Jung; Park, Jang-Hyun

    2016-06-01

    Inactive space objects are usually rotating and tumbling as a result of internal or external forces. KOREASAT 1 has been inactive since 2005, and its drift trajectory has been monitored with the optical wide-field patrol network (OWL-Net). However, a quantitative analysis of KOREASAT 1 in regard to the attitude evolution has never been performed. Here, two optical tracking systems were used to acquire raw measurements to analyze the rotation period of two inactive satellites. During the optical campaign in 2013, KOREASAT 1 was observed by a 0.6 m class optical telescope operated by the Korea Astronomy and Space Science Institute (KASI). The rotation period of KOREASAT 1 was analyzed with the light curves from the photometry results. The rotation periods of the low Earth orbit (LEO) satellite ASTRO-H after break-up were detected by OWL-Net on April 7, 2016. We analyzed the magnitude variation of each satellite by differential photometry and made comparisons with the star catalog. The illumination effect caused by the phase angle between the Sun and the target satellite was corrected with the system tool kit (STK) and two line element (TLE) technique. Finally, we determined the rotation period of two inactive satellites on LEO and geostationary Earth orbit (GEO) with light curves from the photometry. The main rotation periods were determined to be 5.2 sec for ASTRO-H and 74 sec for KOREASAT 1.

  15. LEO-to-ground polarization measurements aiming for space QKD using Small Optical TrAnsponder (SOTA).

    PubMed

    Carrasco-Casado, Alberto; Kunimori, Hiroo; Takenaka, Hideki; Kubo-Oka, Toshihiro; Akioka, Maki; Fuse, Tetsuharu; Koyama, Yoshisada; Kolev, Dimitar; Munemasa, Yasushi; Toyoshima, Morio

    2016-05-30

    Quantum communication, and more specifically Quantum Key Distribution (QKD), enables the transmission of information in a theoretically secure way, guaranteed by the laws of quantum physics. Although fiber-based QKD has been readily available since several years ago, a global quantum communication network will require the development of space links, which remains to be demonstrated. NICT launched a LEO satellite in 2014 carrying a lasercom terminal (SOTA), designed for in-orbit technological demonstrations. In this paper, we present the results of the campaign to measure the polarization characteristics of the SOTA laser sources after propagating from LEO to ground. The most-widely used property for encoding information in free-space QKD is the polarization, and especially the linear polarization. Therefore, studying its behavior in a realistic link is a fundamental step for proving the feasibility of space quantum communications. The results of the polarization preservation of two highly-polarized lasers are presented here, including the first-time measurement of a linearly-polarized source at λ = 976 nm and a circularly-polarized source at λ = 1549 nm from space using a realistic QKD-like receiver, installed in the Optical Ground Station at the NICT Headquarters, in Tokyo, Japan. PMID:27410141

  16. Synergic use of satellite and ground based remote sensing methods for monitoring the San Leo rock cliff (Northern Italy)

    NASA Astrophysics Data System (ADS)

    Frodella, William; Ciampalini, Andrea; Gigli, Giovanni; Lombardi, Luca; Raspini, Federico; Nocentini, Massimiliano; Scardigli, Cosimo; Casagli, Nicola

    2016-07-01

    The historic town of San Leo (Emilia Romagna Region, northern Italy) is located on top of an isolated rock massif above the Marecchia River valley hillside. On February 27th 2014, a northeastern sector of the massif collapsed; minor structural damages were reported in the town and a few buildings were evacuated as a precautionary measure. Although no fatalities occurred and the San Leo cultural heritage suffered no damage, minor rock fall events kept taking place on the newly formed rock wall, worsening this hazardous situation. In this framework, a monitoring system based on remote sensing techniques, such as radar interferometry (both spaceborne and ground-based) and terrestrial laser scanning, was planned in order to monitor the ground deformation of the investigated area and to evaluate the residual risk. In this paper the main outlines of a 1-year monitoring activity are described, including a pre-event analysis of possible landslide precursors and a post-event analysis of the displacements of both the collapse-affected rock wall sector and the rock fall deposits.

  17. Leo Beranek's contributions to architectural acoustics from development of criteria for design to practical applications in buildings of all types

    NASA Astrophysics Data System (ADS)

    Cavanaugh, William J.

    2001-05-01

    This paper traces Leo Beranek's continuing contributions in architectural acoustics since the author joined the consulting staff of Bolt Beranek and Newman Inc. in February 1954. They are legion, including room acoustics, sound and vibration transmission, control of ambient noise from building mechanical electrical and plumbing systems, electrocoustic applications and other issues through the evaluation of the finished building spaces themselves. While Beranek's classic texts, Acoustical Measurements (1948) and Acoustics (1954) served as essential references for the early BBN staff, criteria in architectural acoustics were severely limited if not nonexistent. If he did not take up the challenge to fill a criterion gap, his inspirational leadership guided others to do so, as it did the author and colleagues trying to better understand speech privacy in buildings. Beranek's real labor of love in architectural acoustics is in understanding music performance halls. Beranek's dedicated research over a span of five decades has produced countless journal papers in concert hall acoustics as well as three important texts, the most recent in 2003. Leo Beranek's contributions have earned him the Sabine and Gold Medals of the Acoustical Society and countless other honors including most recently the National Medal of Science.

  18. Pavement crack detection combining non-negative feature with fast LoG in complex scene

    NASA Astrophysics Data System (ADS)

    Wang, Wanli; Zhang, Xiuhua; Hong, Hanyu

    2015-12-01

    Pavement crack detection is affected by much interference in the realistic situation, such as the shadow, road sign, oil stain, salt and pepper noise etc. Due to these unfavorable factors, the exist crack detection methods are difficult to distinguish the crack from background correctly. How to extract crack information effectively is the key problem to the road crack detection system. To solve this problem, a novel method for pavement crack detection based on combining non-negative feature with fast LoG is proposed. The two key novelties and benefits of this new approach are that 1) using image pixel gray value compensation to acquisit uniform image, and 2) combining non-negative feature with fast LoG to extract crack information. The image preprocessing results demonstrate that the method is indeed able to homogenize the crack image with more accurately compared to existing methods. A large number of experimental results demonstrate the proposed approach can detect the crack regions more correctly compared with traditional methods.

  19. Soft Expansion of Double-Real-Virtual Corrections to Higgs Production at N$^3$LO

    SciTech Connect

    Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Herzog, Franz; Mistlberger, Bernhard

    2015-05-15

    We present methods to compute higher orders in the threshold expansion for the one-loop production of a Higgs boson in association with two partons at hadron colliders. This process contributes to the N3LO Higgs production cross section beyond the soft-virtual approximation. We use reverse unitarity to expand the phase-space integrals in the small kinematic parameters and to reduce the coefficients of the expansion to a small set of master integrals. We describe two methods for the calculation of the master integrals. The first was introduced for the calculation of the soft triple-real radiation relevant to N3LO Higgs production. The second uses a particular factorization of the three body phase-space measure and the knowledge of the scaling properties of the integral itself. Our result is presented as a Laurent expansion in the dimensional regulator, although some of the master integrals are computed to all orders in this parameter.

  20. Soft Expansion of Double-Real-Virtual Corrections to Higgs Production at N$^3$LO

    DOE PAGES

    Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Herzog, Franz; Mistlberger, Bernhard

    2015-05-15

    We present methods to compute higher orders in the threshold expansion for the one-loop production of a Higgs boson in association with two partons at hadron colliders. This process contributes to the N3LO Higgs production cross section beyond the soft-virtual approximation. We use reverse unitarity to expand the phase-space integrals in the small kinematic parameters and to reduce the coefficients of the expansion to a small set of master integrals. We describe two methods for the calculation of the master integrals. The first was introduced for the calculation of the soft triple-real radiation relevant to N3LO Higgs production. The secondmore » uses a particular factorization of the three body phase-space measure and the knowledge of the scaling properties of the integral itself. Our result is presented as a Laurent expansion in the dimensional regulator, although some of the master integrals are computed to all orders in this parameter.« less

  1. LO Peg: surface differential rotation, flares, and spot-topographic evolution

    NASA Astrophysics Data System (ADS)

    Karmakar, Subhajeet; Pandey, J. C.; Savanov, I. S.; Taş, G.; Pandey, S. B.; Misra, K.; Joshi, S.; Dmitrienko, E. S.; Sakamoto, T.; Gehrels, N.; Okajima, T.

    2016-07-01

    Using the wealth of ˜24 yr multiband data, we present an in-depth study of the star-spot cycles, surface differential rotations (SDR), optical flares, evolution of star-spot distributions, and coronal activities on the surface of young, single, main-sequence, ultrafast rotator LO Peg. From the long-term V-band photometry, we derive rotational period of LO Peg to be 0.4231 ± 0.0001 d. Using the seasonal variations on the rotational period, the SDR pattern is investigated, and shows a solar-like pattern of SDR. A cyclic pattern with period of ˜2.7 yr appears to be present in rotational period variation. During the observations, 20 optical flares are detected with a flare frequency of ˜1 flare per two days and with flare energy of ˜1031-34 erg. The surface coverage of cool spots is found to be in the range of ˜9-26 per cent. It appears that the high- and low-latitude spots are interchanging their positions. Quasi-simultaneous observations in X-ray, UV, and optical photometric bands show a signature of an excess of X-ray and UV activities in spotted regions.

  2. Effectiveness of Space Debris Mitigation Guidelines: Economic Potential of LEO and Traffic Management Issues

    NASA Astrophysics Data System (ADS)

    Belviso, Luciano

    implementation of international technical standards concerning traffic control systems. Applicability of regulatory regime to satellite tracking systems. Even considering the effectiveness of traffic control systems, the most part of accident will be caused by part of operating system floating without guidance. In this case, both the Outer Space Treaty[5] and the Liability Convention[6] only apply if the space object, or part of it, is identifiable. The improvement of tracking system will empower recognition capabilities and will allow to predict with a certain precision to what space object the debris belongs and, also considering the growing number of space objects, it will be possible to identify the fatherhood of a single debris with a certain confidence. The question concerning international law is whether an information relying on simulated and algorithm-based interpretation can be considered like an observed dataset. In other words, in the case one could identify a debris responsible for a damage using simulation, a standard for the whole identification procedure is needed in order to ensure a minimum requirement in terms of accuracy of the model used. These implications will be considered in our paper. References [1] Greenberg, Economic Implications of Orbital Debris Mitigation [LEO Missions], Proceedings of the 48th International Astronautical Congress, IAA-97-IAA-6.5.08, 1997 [2] Art. 33 of the International Telecommunication Convention (ITC) considers that the Geostationary Orbit is a "limited natural resource (which) must be used efficiently and economically so that countries or groups of countries may have equitable access [...]". [3] Collins and Williams, Towards traffic control systems for near-earth space, Proceedings of the 29th colloqium on the law of Outer Space, IISL, 1986, p.166. [4] Dittberner, Fudge, Huth, Johnson, McKnight, Examining siclifying assumption of probability of collisions in LEO, Proceedings of the first European conference on Space Debris

  3. The causal role of the occipital face area (OFA) and lateral occipital (LO) cortex in symmetry perception.

    PubMed

    Bona, Silvia; Cattaneo, Zaira; Silvanto, Juha

    2015-01-14

    Symmetry is an important cue in face and object perception. Here we used fMRI-guided transcranial magnetic stimulation (TMS) to shed light on the role of the occipital face area (OFA), a key region in face processing, and the lateral occipital (LO) cortex, a key area in object processing, in symmetry detection. In the first experiment, we applied TMS over the rightOFA, its left homolog (leftOFA), rightLO, and vertex (baseline) while participants were discriminating between symmetric and asymmetric dot patterns. Stimulation of rightOFA and rightLO impaired performance, causally implicating these two regions in detection of symmetry in low-level dot configurations. TMS over rightLO but not rightOFA also significantly impaired detection of nonsymmetric shapes defined by collinear Gabor patches, demonstrating that rightOFA responds to symmetry but not to all cues mediating figure-ground segregation. The second experiment showed a causal role for rightOFA but not rightLO in facial symmetry detection. Overall, our results demonstrate that both the rightOFA and rightLO are sensitive to symmetry in dot patterns, whereas only rightOFA is causally involved in facial symmetry detection.

  4. Cocaine withdrawal in rats selectively bred for low (LoS) versus high (HiS) saccharin intake

    PubMed Central

    Radke, Anna K.; Zlebnik, Natalie E.; Carroll, Marilyn E.

    2014-01-01

    Cocaine use results in anhedonia during withdrawal, but it is not clear how this emotional state interacts with an individual's vulnerability for addiction. Rats selectively bred for high (HiS) or low (LoS) saccharin intake are a well-established model of drug abuse vulnerability, with HiS rats being more likely to consume sweets and drugs of abuse such as cocaine and heroin (Carroll et al. 2002) than LoS rats. This study examined whether the motivational consequences of cocaine withdrawal are differentially expressed in HiS and LoS rats. HiS and LoS rats were trained to respond for a sucrose reward on a progressive ratio (PR) schedule of reinforcement and breakpoints were measured during and after chronic, continuous exposure to cocaine (30 mg/kg/day). Cocaine, but not saline, treatment resulted in lower breakpoints for sucrose during withdrawal in LoS rats only. These results suggest anhedonia during withdrawal is more pronounced in the less vulnerable LoS rats. Fewer motivational deficits during withdrawal may contribute to drug vulnerability in the HiS line. PMID:25482327

  5. Cocaine withdrawal in rats selectively bred for low (LoS) versus high (HiS) saccharin intake.

    PubMed

    Radke, Anna K; Zlebnik, Natalie E; Carroll, Marilyn E

    2015-02-01

    Cocaine use results in anhedonia during withdrawal, but it is not clear how this emotional state interacts with an individual's vulnerability for addiction. Rats selectively bred for high (HiS) or low (LoS) saccharin intake are a well-established model of drug abuse vulnerability, with HiS rats being more likely to consume sweets and drugs of abuse such as cocaine and heroin (Carroll et al., 2002) than LoS rats. This study examined whether the motivational consequences of cocaine withdrawal are differentially expressed in HiS and LoS rats. HiS and LoS rats were trained to respond for a sucrose reward on a progressive ratio (PR) schedule of reinforcement and breakpoints were measured during and after chronic, continuous exposure to cocaine (30 mg/kg/day). Cocaine, but not saline, treatment resulted in lower breakpoints for sucrose during withdrawal in LoS rats only. These results suggest anhedonia during withdrawal is more pronounced in the less vulnerable LoS rats. Fewer motivational deficits during withdrawal may contribute to greater drug vulnerability in the HiS line.

  6. Improved Photometry of Sloan Digital Sky Survey Crowded-Field Images: Structure and Dark Matter Content in the Dwarf Spheroidal Galaxy Leo I

    NASA Astrophysics Data System (ADS)

    Smolčić, V.; Zucker, D. B.; Bell, E. F.; Coleman, M. G.; Rix, H. W.; Schinnerer, E.; Ivezić, Ž.; Kniazev, A.

    2007-11-01

    We explore how well crowded-field point-source photometry can be accomplished with Sloan Digital Sky Survey (SDSS) data. For this purpose, we present a photometric pipeline based on DoPHOT and tuned for analyzing crowded-field images from the SDSS. Using Monte Carlo simulations we show that the completeness of source extraction is above 80% to an i-band AB magnitude of lesssim21 and a stellar surface density of ~200 arcmin-2. Hence, a specialized data pipeline can be efficiently used for, e.g., nearby resolved galaxies in SDSS images, where the standard SDSS photometric package Photo, when applied in normal survey mode, gives poor results. We apply our pipeline to an area of ~3.55 deg2 around the dwarf spheroidal galaxy (dSph) Leo I and construct a high signal-to-noise ratio star count map of Leo I via an optimized filter in color-magnitude space (g, r, i). This filter reduces the foreground contamination by ~80% and enhances the central stellar surface density contrast of the dwarf by a factor of gtrsim4, making this study the deepest wide-field study of the Leo I dSph based on accurate CCD photometry. Although the radial surface density profile deviates from the best-fit empirical King model toward outer radii, we find no evidence for tidal debris out to a stellar surface density of 4 × 10-3 of the central value. We determine the total luminosity of Leo I and model its mass using the spherical and isotropic Jeans equation. Assuming that mass follows light, we constrain a lower limit on the total mass of the dSph to be (1.7 ± 0.2) × 107 Modot. On the other hand, if the mass in Leo I is dominated by a constant-density dark matter (DM) halo, then the mass within the central 12‧ is (2 ± 0.6) × 108 Modot. This leads to a mass-to-light ratio of Gt6 in I-band solar units, and possibly >75 if the DM halo dominates the mass and extends further out than 12‧. In summary, our results show that Leo I is a symmetric, relaxed, and bound system; this supports the idea

  7. Lo-Cal, Champaign, Illinois solar-energy-system performance evaluation, Jan. 1982 - Apr. 1982

    NASA Astrophysics Data System (ADS)

    Spears, J. W.

    1982-06-01

    Performance data on a solar heated house are given. The Lo-Cal site is a single family residence in Illinois with a direct gain solar heating system equipped with 200 square feet of south facing triple glazed windows and an auxiliary 84,000 Btu hour forced air furnace. For the months of January through April 1982, the solar fraction was found to be 29%, corresponding to a saving of 3107 kWh of conventional fuel. Monthly performance data are tabulated for the overall system, and for the collector and space heating subsystems. Also tabulated are monthly energy savings, weather, and passive system environment data. The building's performance is illustrated by graphs for each month of the daily insolation, auxiliary heat, building temperature, and ambient temperature.

  8. On the Higgs cross section at N3LO+N3LL and its uncertainty

    NASA Astrophysics Data System (ADS)

    Bonvini, Marco; Marzani, Simone; Muselli, Claudio; Rottoli, Luca

    2016-08-01

    We consider the inclusive production of a Higgs boson in gluon-fusion and we study the impact of threshold resummation at next-to-next-to-next-to-leading logarithmic accuracy (N3LL) on the recently computed fixed-order prediction at next-to-next-to-next-to-leading order (N3LO). We propose a conservative, yet robust way of estimating the perturbative uncertainty from missing higher (fixed- or logarithmic-) orders. We compare our results with two other different methods of estimating the uncertainty from missing higher orders: the Cacciari-Houdeau Bayesian approach to theory errors, and the use of algorithms to accelerate the convergence of the perturbative series, as suggested by David and Passarino. We confirm that the best convergence happens at μ R = μ F = m H /2, and we conclude that a reliable estimate of the uncertainty from missing higher orders on the Higgs cross section at 13 TeV is approximately ±4%.

  9. HIEN-LO: An experiment for charge determination of cosmic rays of interplanetary and solar origin

    NASA Technical Reports Server (NTRS)

    Klecker, B.; Hovestadt, D.; Mason, G. M.; Blake, J. B.; Nicholas, J.

    1988-01-01

    The experiment is designed to measure the heavy ion environment at low altitude (HIEN-LO) in the energy range 0.3 to 100 MeV/nucleon. In order to cover this wide energy range a complement of three sensors is used. A large area ion drift chamber and a time-of-flight telescope are used to determine the mass and energy of the incoming cosmic rays. A third omnidirectional counter serves as a proton monitor. The analysis of mass, energy and incoming direction in combination with the directional geomagnetic cut-off allows the determination of the ionic charge of the cosmic rays. The ionic charge in this energy range is of particular interest because it provides clues to the origin of these particles and to the plasma conditions at the acceleration site. The experiment is expected to be flown in 1988/1989.

  10. Vanishing absorption and blueshifted emission in FeLoBAL quasars

    NASA Astrophysics Data System (ADS)

    Rafiee, Alireza; Pirkola, Patrik; Hall, Patrick B.; Galati, Natalee; Rogerson, Jesse; Ameri, Abtin

    2016-07-01

    We study the dramatic decrease in iron absorption strength in the iron low-ionization broad absorption line quasar SDSS J084133.15+200525.8. We report on the continued weakening of absorption in the prototype of this class of variable broad absorption line quasar, FBQS J140806.2+305448. We also report a third example of this class, SDSS J123103.70+392903.6; unlike the other two examples, it has undergone an increase in observed continuum brightness (at 3000 Å rest frame) as well as a decrease in iron absorption strength. These changes could be caused by absorber transverse motion or by ionization variability. We note that the Mg II and UV Fe II lines in several FeLoBAL quasars are blueshifted by thousands of km s-1 relative to the H β emission line peak. We suggest that such emission arises in the outflowing winds normally seen only in absorption.

  11. Screening materials with the XIA UltraLo alpha particle counter at Southern Methodist University

    SciTech Connect

    Nakib, M. Z.; Cooley, J.; Kara, B.; Qiu, H.; Scorza, S.; Guiseppe, V. E.; Rielage, K.; Schnee, R. W.

    2013-08-08

    Southern Methodist University houses one of five existing commercially available UltraLo 1800 production model alpha counters made by XIA LLC. The instrument has an electron drift chamber with a 707 cm{sup 2} or 1800 cm{sup 2} counting region which is determined by selecting the inner electrode size. The SMU team operating this device is part of the SuperCDMS screening working group, and uses the alpha counter to study the background rates from the decay of radon in materials used to construct the SuperCDMS experiment. We have studied four acrylic samples obtained from the MiniCLEAN direct dark matter search with the XIA instrument demonstrating its utility in low background experiments by investigating the plate-out of {sup 210}Pb and comparing the effectiveness of cleaning procedures in removing {sup 222}Rn progenies from the samples.

  12. Bayesian estimation of Karhunen-Loève expansions; A random subspace approach

    NASA Astrophysics Data System (ADS)

    Chowdhary, Kenny; Najm, Habib N.

    2016-08-01

    One of the most widely-used procedures for dimensionality reduction of high dimensional data is Principal Component Analysis (PCA). More broadly, low-dimensional stochastic representation of random fields with finite variance is provided via the well known Karhunen-Loève expansion (KLE). The KLE is analogous to a Fourier series expansion for a random process, where the goal is to find an orthogonal transformation for the data such that the projection of the data onto this orthogonal subspace is optimal in the L2 sense, i.e., which minimizes the mean square error. In practice, this orthogonal transformation is determined by performing an SVD (Singular Value Decomposition) on the sample covariance matrix or on the data matrix itself. Sampling error is typically ignored when quantifying the principal components, or, equivalently, basis functions of the KLE. Furthermore, it is exacerbated when the sample size is much smaller than the dimension of the random field. In this paper, we introduce a Bayesian KLE procedure, allowing one to obtain a probabilistic model on the principal components, which can account for inaccuracies due to limited sample size. The probabilistic model is built via Bayesian inference, from which the posterior becomes the matrix Bingham density over the space of orthonormal matrices. We use a modified Gibbs sampling procedure to sample on this space and then build probabilistic Karhunen-Loève expansions over random subspaces to obtain a set of low-dimensional surrogates of the stochastic process. We illustrate this probabilistic procedure with a finite dimensional stochastic process inspired by Brownian motion.

  13. Downregulation of MDM2 expression by RNAi inhibits LoVo human colorectal adenocarcinoma cells growth and the treatment of LoVo cells with mdm2siRNA3 enhances the sensitivity to cisplatin

    SciTech Connect

    Yu Yan . E-mail: gyfyuyan@hotmail.com; Sun Ping . E-mail: sunny19750502@hotmail.com; Sun Lichun; Liu Guoyi; Chen Guohua . E-mail: olivebranch_82@hotmail.com; Shang Lihua . E-mail: leval1000@sina.com; Wu Hongbo . E-mail: whpwl@sina.com; Hu Jing; Li Yue; Mao Yinling; Sui Guangjie; Sun Xiwen

    2006-01-06

    To investigate the biological effect of mdm2 in human colorectal adenocarcinoma LoVo cells, three mdm2siRNA constructions were recombinated and transient transfected into human colorectal adenocarcinoma LoVo cells with low differentiation character in vitro. The results showed that mdm2siRNA3 reduced mRNA level of mdm2 and protein level of mdm2, leading to proliferation inhibition on LoVo cells, and reduced tumor growth in nude mice. It was found that depletion of MDM2 in this pattern promoted apoptosis of LoVo cells and Cisplatin (DDP) treated in the mdm2siRNA3 transfected cell population would result in a substantial decrease by MTT colorimetry. Decreasing the MDM2 protein level in LoVo cells by RNAi could significantly inhibit tumor growth both in vitro and in vivo, which indicated that mdm2 gene played a definite role in the development and aggressiveness of human colon carcinoma. It also could be a therapeutic target in colorectal carcinoma. The synergistic activation of RNAi and cell toxicity agents indicated that the combination of chemotherapy and gene therapy will be a promising approach in the future.

  14. Space radiation environment prediction for VLSI microelectronics devices onboard a LEO satellite using OMERE-TRAD software

    NASA Astrophysics Data System (ADS)

    Sajid, Muhammad; Chechenin, N. G.; Torres, Frank Sill; Khan, E. U.; Agha, Shahrukh

    2015-07-01

    Space radiation environment at Low Earth Orbits (LEO) with perigee at 300 km, apogee at 600 km altitude having different orbital inclinations was modeled in the form of electrons and protons trapped in Van Allen Earth Radiation Belts (ERBs), heavy ions and protons in Galactic Cosmic Rays (GCRs), and Energetic Solar Particles (ESP) Events during solar maximum period. The co-relation between various shielding thicknesses and particles transport flux was analyzed for this specific orbit. We observed that there is an optimum shield thickness above which the attenuation of the transmitted flux of incident particles is negligible. To estimate the orbit average differential and integral fluxes to be encountered by onboard devices an appropriate radiation environment models were chosen in OMERE-TRAD toolkit and the impact of various shielding thickness for different orbital inclinations on integral Linear-Energy-Transfer (LET) spectra were determined.

  15. Further studies on Toxascaris leonina (Linstow, 1902) (Ascaridida: Ascarididae) from Felis lynx (Linnaeus) and Panthera leo (Linnaeus) (Carnivora: Felidae).

    PubMed

    Xue, Li-Mei; Chai, Jing-Bo; Guo, Yan-Ning; Zhang, Lu-Ping; Li, Liang

    2014-03-01

    Toxascaris leonina (Linstow, 1902) is a most common intestinal parasite of various animals in Felidae and Canidae. In the present paper, light and scanning electron microscopy (SEM) were used to study the morphological aspects of adult worms of this nematode in detail, based on the material collected from Panthera leo (Linnaeus) and Felis lynx (Linnaeus) (Carnivora: Felidae) in China. The results showed that there were some morphometric differences between the present material and the previous studies, including the body size, the width and length of cervical alae, the number of denticles on each lip and the tail length of the female. Previously unreported morphological features were also revealed. These supplementary morphological and morphometric data contributed to a more accurate identification of this worldwide distributed ascarid nematode.

  16. Estimated performance and future potential of solar dynamic and photovoltaic power systems for selected LEO and HEO missions

    NASA Technical Reports Server (NTRS)

    Bents, David J.; Lu, Cheng Y.

    1989-01-01

    Solar photovoltaic and thermal dynamic power systems for application to selected low-earth-orbit (LEO) and high-earth-orbit (HEO) missions are characterized in the regime 7 to 35 kWe. Input parameters to the characterization are varied to correspond to anticipated introduction of improved or new technologies. A comparative assessment is made of the two power system types for emerging technologies in cells and arrays, energy storage, optical surfaces, heat engines, thermal energy storage and thermal management. The assessment is made to common ground rules and assumptions. The four missions (Space Station, sun-synchronous, Van Allen belt, and GEO) are representative of the anticipated range of multikilowatt earth-orbit missions. The results give the expected performance, mass and drag of multikilowatt earth-orbiting solar power systems and show how the overall system figure of merit will improve as new component technologies are incorporated.

  17. A CubeSAT payload for in-situ monitoring of pentacene degradation due to atomic oxygen etching in LEO

    NASA Astrophysics Data System (ADS)

    Gorreta, Sergi; Pons-Nin, Joan; López, Gema; Figueras, Eduard; Jové-Casulleras, Roger; Araguz, Carles; Via, Pol; Camps, Adriano; Domínguez-Pumar, Manuel

    2016-09-01

    This paper reports and discusses the design and ground tests of a CubeSat payload which allows to measure, in-situ and in real time, the degradation of a polymer of electronic interest due to atomic oxygen etching in LEO. It provides real-time information on how the degradation occurs, eliminating the need to work with samples recovered once the mission has finished. The polymer, TIPS-Pentacene, is deposited on the surface of a microelectromechanical (MEMS) cantilever, which works as a resonator embedded in a Pulsed Digital Oscillator circuit. The mass losses in the polymer due to atomic oxygen corrosion produce variations in the resonant frequency of the MEMS, which is continuously sensed by the circuit and transmitted to the ground. This way, polymer mass losses around 10-12 kg can be detected during the mission. The payload is a part of the 3Cat-1 mission, a nano-satellite aimed at carrying out several scientific experiments.

  18. TIDAL SIGNATURES IN THE FAINTEST MILKY WAY SATELLITES: THE DETAILED PROPERTIES OF LEO V, PISCES II, AND CANES VENATICI II

    SciTech Connect

    Sand, David J.; Strader, Jay; McLeod, Brian; Caldwell, Nelson; Willman, Beth; Zaritsky, Dennis; Olszewski, Edward; Seth, Anil

    2012-09-01

    We present deep wide-field photometry of three recently discovered faint Milky Way (MW) satellites: Leo V, Pisces II, and Canes Venatici II. Our main goals are to study the structure and star formation history of these dwarfs; we also search for signs of tidal disturbance. The three satellites have similar half-light radii ({approx}60-90 pc) but a wide range of ellipticities. Both Leo V and CVn II show hints of stream-like overdensities at large radii. An analysis of the satellite color-magnitude diagrams shows that all three objects are old (>10 Gyr) and metal-poor ([Fe/H] {approx} -2), though neither the models nor the data have sufficient precision to assess when the satellites formed with respect to cosmic reionization. The lack of an observed younger stellar population ({approx}< 10 Gyr) possibly sets them apart from the other satellites at Galactocentric distances {approx}> 150 kpc. We present a new compilation of structural data for all MW satellite galaxies and use it to compare the properties of classical dwarfs to the ultra-faints. The ellipticity distribution of the two groups is consistent at the {approx}2{sigma} level. However, the faintest satellites tend to be more aligned toward the Galactic Center, and those satellites with the highest ellipticity ({approx}> 0.4) have orientations ({Delta}{theta}{sub GC}) in the range 20 Degree-Sign {approx}< {Delta}{theta}{sub GC} {approx}< 40 Degree-Sign . This latter observation is in rough agreement with predictions from simulations of dwarf galaxies that have lost a significant fraction of their dark matter halos and are being tidally stripped.

  19. Characterization of the Catalog Fengyun-1C Fragments and Their Long-term Effect on the LEO Environment

    NASA Technical Reports Server (NTRS)

    Liou, J.-C.; Johnson, N. L.

    2008-01-01

    The intentional breakup of Fengyun-1C on 11 January 2007 created the most severe orbital debris cloud in history. More than 2500 large fragments were identified and tracked by the U.S. Space Surveillance Network by the end of the year. The altitude where the event occurred was probably the worst location for a major breakup in the low Earth orbit (LEO) region, since it was already highly populated with operational satellites and debris generated from previous breakups. The addition of so many fragments not only poses a realistic threat to operational satellites in the region, but also increases the instability (i.e., collision cascade effect) of the debris population there. Preliminary analysis of the large Fengyun-1C fragments indicates that their size and area-to-mass ratio (A/M) distributions are very different from those of other known events. About half of the fragments appear to be composed of light-weight materials and more than 100 of them have A/M values exceeding 1 square meter per kilogram, consistent with thermal blanket pieces. In addition, the orbital elements of the fragments suggest nontrivial velocity gain by the fragment cloud during the impact. These important characteristics were incorporated into a numerical simulation to assess the long-term impact of the Fengyun-1C fragments to the LEO debris environment. The main objectives of the simulation were to evaluate (1) the collision probabilities between the Fengyun-1C fragments and the rest of the catalog population and (2) the collision activities and population growth in the region in the next 100 years.

  20. Cutting edge: CXCR4-Lo: molecular cloning and functional expression of a novel human CXCR4 splice variant.

    PubMed

    Gupta, S K; Pillarisetti, K

    1999-09-01

    Human CXCR4 is a specific receptor for the CXC chemokine stromal cell-derived factor-1 (SDF-1) and a coreceptor for T cell line tropic strains of HIV-1. Genetic knockouts of CXCR4 and SDF-1 have delineated their critical role during embryonic cardiogenesis, leukopoiesis, and vasculogenesis. Herein, we used bioinformatics and differential strategies like isoform-specific RT-PCR and Northern blots to identify and clone a novel unspliced isoform of human CXCR4, termed CXCR4-Lo. CXCR4-Lo corresponds to a larger approximately 4. 0-kb mRNA transcript and differs from the known human CXCR4 by the first 9 aa in the functionally important NH2-terminal extracellular domain of the receptor. CXCR4-Lo-transfected rat basophil leukemia-2H3 cells responded to SDF-1 with a transient rise of intracellular Ca2+ concentration and by undergoing chemotaxis. Expression of CXCR4-Lo is noteworthy, as it may have differential affinity as a coreceptor for HIV strains in comparison with CXCR4. Furthermore, CXCR4-Lo may also provide a functional backup to CXCR4 during embryogenesis.

  1. RIN1-Ras-ERK pathway plays an important role in carcinogenesis in colon cancer cell line LoVo.

    PubMed

    Inoue, Takeshi; Goi, Takanori; Hirono, Yasuo; Katayama, Kanji; Yamaguchi, Akio

    2011-01-01

    The RIN1 protein has SH2, three domains, and H-Ras binding domains; thus, it is presumed to be an important molecule in an intracellular signaling pathway. We examined the effect of the introduction of a membrane protein-encoding, mutated (S351A)RIN1 gene into a colon cancer. In the LoVo colon cancer cell line, endogenous RIN1 protein was strongly expressed in the cytoplasmic fraction, and the RIN1 protein in the cytoplasmic fraction was strongly bound to the 14-3-3 protein. In the mutated (S351A)RIN1-transfected LoVo cells, the mutated (S351A)RIN1 protein was identified in the cell membrane, and was bound to HRas protein. Also, in vitro the proliferative capacity of the mutated (S351A)RIN1-transfected LoVo cells was significantly inhibited, compared with that of their empty vector-transfected counterparts. In the mutated (S351A)RIN1-transfected LoVo cells, the phosphorylation of ERK1/2 proteins downstream of the H-Ras molecule was inhibited, compared with the counterparts. This study is the first to show that the localization of RIN1 protein plays an important role in the carcinogenesis in colon cancer cells LoVo (i.e., signal transduction in the Ras-ERK pathway).

  2. Summary of LO2/Ethanol OMS/RCS Technology and Advanced Development 99-2744

    NASA Technical Reports Server (NTRS)

    Curtis, Leslie A.; Hurlbert, Eric A.

    1999-01-01

    NASA is pursuing non-toxic propellant technologies applicable to RLV and Space Shuttle orbital maneuvering system (OMS) and reaction control system (RCS). The primary objectives of making advancements in an OMS/RCS system are improved safety, reliability, and reduced operations and maintenance cost, while meeting basic operational and performance requirements. An OMS/RCS has a high degree of direct interaction with the vehicle and crew and requires subsystem and components that are compatible with integration into the vehicle with regard to external mold-line, power, and thermal control. In July 1997, a Phase I effort for the technology and advanced development of an upgrade of the space shuttle was conducted to define the system architecture, propellant tank, feed system, RCS thrusters, and OMS engine. Phase I of the project ran from July 1997 to October 1998. Phase II is currently being planned for the development and test of full-scale prototype of the system in 1999 and 2000. The choice of pressure-fed liquid oxygen (LO2) and ethanol is the result of numerous trade studies conducted from 1980 to 1996. Liquid oxygen and ethanol are clean burning, high-density propellants that provide a high degree of commonality with other spacecraft subsystems including life support, power, and thermal control, and with future human exploration and development of space missions. The key to this pressure-fed system is the use of subcooled liquid oxygen at 350 psia. In this approach, there is 80 degrees R of subcooling, which means that boil-off will not occur until the temperature has risen 80 R. The sub-cooling results naturally from loading propellants at 163 R, which is the saturation temperature at 14.7 psia, and then pressurizing to 350 psia on the launch pad. Thermal insulation and conditioning techniques are then used to limit the LO2 temperature to 185 R maximum, and maintain the sub-cooling. The other key is the wide temperature range of ethanol, -173 F to +300 F, which

  3. Effects of anaesthesia on proliferation, invasion and apoptosis of LoVo colon cancer cells in vitro.

    PubMed

    Xu, Y J; Li, S Y; Cheng, Q; Chen, W K; Wang, S L; Ren, Y; Miao, C H

    2016-02-01

    Tumour cell proliferation, invasion and apoptosis are crucial steps in tumour metastasis. We evaluated the effect of serum from patients undergoing colon cancer surgery receiving thoracic epidural and propofol anaesthesia on colon cancer cell biology. Patients were randomly assigned to receive propofol anaesthesia with a concomitant thoracic epidural (PEA, n = 20) or sevoflurane anaesthesia with opioid analgesia (SGA, n = 20). Venous blood was obtained before induction of anaesthesia and 24 hours postoperatively. The LoVo colon cancer cells were cultured with patient serum from both groups and the effects on proliferation, invasion and apoptosis were measured. Twenty-four hours after surgery, the absorbance value of LoVo cells at 10% serum concentration from PEA was decreased when compared with SGA (0.302 (0.026) vs 0.391 (0.066), p = 0.005). The inhibitory rate of LoVo cells at 10% serum concentration from PEA was higher than that from SGA (p = 0.004) 24 h after surgery. The number of invasive LoVo cells at 10% serum concentration from PEA was reduced when compared with SGA (44 (4) vs 62 (4), p < 0.001). Exposure of LoVo cells to postoperative serum from patients receiving PEA led to a higher luminescence ratio (apoptosis) than those receiving SGA (0.36 (0.04) vs 0.27 (0.05), p < 0.001). Serum from patients receiving PEA for colon cancer surgery inhibited proliferation and invasion of LoVo cells and induced apoptosis in vitro more than that from patients receiving SGA. Anaesthetic technique might influence the serum milieu in a way that affects cancer cell biology and, thereby, tumour metastastasis.

  4. Karhunen-Loève expansion revisited for vector-valued random fields: Scaling, errors and optimal basis.

    NASA Astrophysics Data System (ADS)

    Perrin, G.; Soize, C.; Duhamel, D.; Funfschilling, C.

    2013-06-01

    Due to scaling effects, when dealing with vector-valued random fields, the classical Karhunen-Loève expansion, which is optimal with respect to the total mean square error, tends to favorize the components of the random field that have the highest signal energy. When these random fields are to be used in mechanical systems, this phenomenon can introduce undesired biases for the results. This paper presents therefore an adaptation of the Karhunen-Loève expansion that allows us to control these biases and to minimize them. This original decomposition is first analyzed from a theoretical point of view, and is then illustrated on a numerical example.

  5. The LEO Archipelago: A system of earth-rings for communications, mass-transport to space, solar power, and control of global warming

    NASA Astrophysics Data System (ADS)

    Meulenberg, Andrew; Karthik Balaji, P. S.

    2011-06-01

    Man's quest to get into space is hindered by major problems (e.g., system-development and capital costs, expense of putting mass into orbit, trapped-radiation belts, and environmental impact of a large increase in rocket launches). A multi-purpose low-earth-orbit system of rings circling the earth - the "LEO ARCHIPELAGO TM" - is proposed as a means of solving or bypassing many of them. A fiber-optic ring about the earth would be an initial testing and developmental stage for the Ring Systems, while providing cash-flow through a LEO-based, high-band-width, world-wide communication system. A low-earth-orbit-based space-elevator system, "Sling-on-a-Ring TM", is proposed as the crucial developmental stage of the LEO Archipelago. Being a LEO-based heavy-mass lifter, rather than earth- or GEO-based, it is much less massive and therefore less costly than other proposed space-elevators. With the advent of lower-cost, higher-mass transport to orbit, the options for further space development (e.g., space solar power, radiation, and space-debris dampers, sun shades, and permanent LEO habitation) are greatly expanded. This paper provides an update of the Sling-on-a-Ring concept in terms of new materials, potential applications, and trade-offs associated with an earlier model. The impact of Colossal Carbon Tubes, CCT, a new material with high tensile strength, extremely-low density, and other favorable properties, and other new technologies (e.g., solar-powered lasers, power beaming to near-space and earth, and thermal-control systems) on the development of associated LEO-Ring systems is also explored. The material's effect on the timeline for the system development indicates the feasibility of near-term implementation of the system (possibly within the decade). The Sling-on-a-Ring can provide a less-expensive, environment-friendly mode of access to space. This would pave the way (via eventual operation at >1000 t per day by 2050) for large scale development of space

  6. Study of LO-phonon decay in semiconductors for hot carrier solar cell

    NASA Astrophysics Data System (ADS)

    Levard, Hugo; Vidal, Julien; Laribi, Sana; Guillemoles, Jean-François

    2014-03-01

    Knowledge of phonon decay is of crucial importance when studying basic properties of semiconductors, since they are closely related to Raman linewidth and non-equilibrium-hot-carriers cooling. The latter indeed cools down to the bottom of the conduction band within a picosecond range because of electron-phonon interaction. The eventual emitted hot phonons then decay in few picoseconds. The hot carriers cooling can be slowed down by considering the decay rate dependence of phonon on conservation rules, whose tuning may reduce the allowed two-phonon final states density. This is of direct interest for the third generation photovoltaic devices that are Hot Carrier Solar Cells (HCSC), in which the photoexcited carriers are extracted at an energy higher than thermal equilibrium. One of the HCSC main challenges then is to find an absorber material in which the hot phonons has a relaxation time longer than the carriers cooling time, so that we can expect the electron to ``reabsorb'' a phonon, slowing down the electronic cooling. HCSC yield is ultimately limited by LO phonon decay, though. In this work, we present theoretical results obtained from ab initio calculations of phonon lifetime in III-V and IV-IV semiconductors through a three-phonon process. Common approximations in the literature are questioned. In particular, we show that the usual ``zone-center approximation'' is not valid in some specific semiconductors. The analysis allows to correctly investigate phonon decay mechanisms in bulk and nanostructured materials.

  7. Optimized suppression of coherent noise from seismic data using the Karhunen-Loève transform.

    PubMed

    Montagne, Raúl; Vasconcelos, Giovani L

    2006-07-01

    Signals obtained in land seismic surveys are usually contaminated with coherent noise, among which the ground roll (Rayleigh surface waves) is of major concern for it can severely degrade the quality of the information obtained from the seismic record. This paper presents an optimized filter based on the Karhunen-Loève transform for processing seismic images contaminated with ground roll. In this method, the contaminated region of the seismic record, to be processed by the filter, is selected in such way as to correspond to the maximum of a properly defined coherence index. The main advantages of the method are that the ground roll is suppressed with negligible distortion of the remnant reflection signals and that the filtering procedure can be automated. The image processing technique described in this study should also be relevant for other applications where coherent structures embedded in a complex spatiotemporal pattern need to be identified in a more refined way. In particular, it is argued that the method is appropriate for processing optical coherence tomography images whose quality is often degraded by coherent noise (speckle).

  8. 3D Building Modeling in LoD2 Using the CityGML Standard

    NASA Astrophysics Data System (ADS)

    Preka, D.; Doulamis, A.

    2016-10-01

    Over the last decade, scientific research has been increasingly focused on the third dimension in all fields and especially in sciences related to geographic information, the visualization of natural phenomena and the visualization of the complex urban reality. The field of 3D visualization has achieved rapid development and dynamic progress, especially in urban applications, while the technical restrictions on the use of 3D information tend to subside due to advancements in technology. A variety of 3D modeling techniques and standards has already been developed, as they gain more traction in a wide range of applications. Such a modern standard is the CityGML, which is open and allows for sharing and exchanging of 3D city models. Within the scope of this study, key issues for the 3D modeling of spatial objects and cities are considered and specifically the key elements and abilities of CityGML standard, which is used in order to produce a 3D model of 14 buildings that constitute a block at the municipality of Kaisariani, Athens, in Level of Detail 2 (LoD2), as well as the corresponding relational database. The proposed tool is based upon the 3DCityDB package in tandem with a geospatial database (PostgreSQL w/ PostGIS 2.0 extension). The latter allows for execution of complex queries regarding the spatial distribution of data. The system is implemented in order to facilitate a real-life scenario in a suburb of Athens.

  9. Tolerance of the frequency deviation of LO sources at a MIMO system

    NASA Astrophysics Data System (ADS)

    Xiao, Jiangnan; Li, Xingying; Zhang, Zirang; Xu, Yuming; Chen, Long; Yu, Jianjun

    2015-11-01

    We analyze and simulate the tolerance of frequency offset at a W-band optical-wireless transmission system. The transmission system adopts optical polarization division multiplexing (PDM), and multiple-input multiple-output (MIMO) reception. The transmission signal adopts optical quadrature phase shift keying (QPSK) modulation, and the generation of millimeter-wave is based on the optical heterodyning technique. After 20-km single-mode fiber-28 (SMF-28) transmission, tens of Gb/s millimeter-wave signal is delivered. At the receiver, two millimeter-wave signals are down-converted into electrical intermediate-frequency (IF) signals in the analog domain by mixing with two electrical local oscillators (LOs) with different frequencies. We investigate the different frequency LO effect on the 2×2 MIMO system performance for the first time, finding that the process during DSP of implementing frequency offset estimation (FOE) before cascaded multi-modulus-algorithm (CMMA) equalization can get rid of the inter-channel interference (ICI) and improve system bit-error-ratio (BER) performance in this type of transmission system.

  10. Biologically based vision simulation for target-background discrimination and camouflage/LO design

    NASA Astrophysics Data System (ADS)

    Doll, Theodore J.; McWhorter, Shane W.; Schmieder, David E.; Hetzler, Morris C.; Stewart, John M.; Wasilewski, Anthony A.; Owens, William R.; Sheffer, Albert D., Jr.; Galloway, Gregory L.; Harbert, Simeon D.

    1997-06-01

    The Georgia Tech Research Institute has developed an integrated suite of software for Visual and Electro-Optical (VISEO) detection analysis, under the sponsorship of the Army Aviation and Troop Command, Aviation Applied Technology Directorate. The VISEO system is a comprehensive workstation-based tool for multi-spectral signature analysis, LO design, and visualization of targets moving through real measured backgrounds. A key component of the VISEO system is a simulation of real measured backgrounds. A key component of the VISEO system is a simulation of human vision, called the Georgia Tech Vision (GTV) simulation. The algorithms used in the simulation are consistent with neurophysiological evidence concerning the functions of the human visual system, from dynamic light adaptation processes in the retinal receptors and ganglia to the processing of motion, color, and edge information in the striate cortex. The simulation accepts images seen by the naked eye or through direct-view optical systems, as well as images viewed on the displays of IR sensors, image intensifiers and night-vision devices. GTV outputs predicted probabilities that the target is fixated (Pfix) during visual search, and detected (Pd), and also identifies specific features of the target that contribute most to successful search and detection performance. This paper outlines the capabilities and structure of the VISEO system, emphasizing GTV. Example results of visible and IR signature reduction on the basis of VISEO will be shown and described.

  11. Aggregation of LoD 1 building models as an optimization problem

    NASA Astrophysics Data System (ADS)

    Guercke, R.; Götzelmann, T.; Brenner, C.; Sester, M.

    3D city models offered by digital map providers typically consist of several thousands or even millions of individual buildings. Those buildings are usually generated in an automated fashion from high resolution cadastral and remote sensing data and can be very detailed. However, not in every application such a high degree of detail is desirable. One way to remove complexity is to aggregate individual buildings, simplify the ground plan and assign an appropriate average building height. This task is computationally complex because it includes the combinatorial optimization problem of determining which subset of the original set of buildings should best be aggregated to meet the demands of an application. In this article, we introduce approaches to express different aspects of the aggregation of LoD 1 building models in the form of Mixed Integer Programming (MIP) problems. The advantage of this approach is that for linear (and some quadratic) MIP problems, sophisticated software exists to find exact solutions (global optima) with reasonable effort. We also propose two different heuristic approaches based on the region growing strategy and evaluate their potential for optimization by comparing their performance to a MIP-based approach.

  12. Effect of position resolution on LoR discrimination for a dual-head Compton camera

    NASA Astrophysics Data System (ADS)

    Gillam, John E.; Beveridge, Toby E.; Boston, Andrew J.; Boston, Helen C.; Cooper, Reynold J.; Hall, Chris J.; Mather, Andrew R.; Nolan, Paul J.; Lewis, Rob A.

    2007-04-01

    With the current increase in effective germanium semiconductor detection technology, a positron emission tomography system comprising two opposing HPGe detectors is under development. This type of detection offers not only improvement to some aspects of PET, but also the ability to record single-photon information in the detection process. This information can be used in stand-alone imaging, and also as an additional information source in the PET process. Discrimination based on this single-photon information was proposed; however, the effectiveness of this discrimination is dependent on the resolution of the single-photon information. Simulations of the detection system, in which the positional resolution of the interaction information is variable, was conducted. The single-photon information has then been used in the PET imaging process and its effect on image improvement shown. Much like mechanical collimation, electronic collimation may be used to remove false LoRs from an image, at the expense of efficiency. Moreover, unlike mechanical collimation, this trade off may be dynamically adjusted post data acquisition.

  13. Cellular stress induced by photodynamic reaction with CoTPPS and MnTMPyPCl5 in combination with electroporation in human colon adenocarcinoma cell lines (LoVo and LoVoDX).

    PubMed

    Kulbacka, J; Kotulska, M; Rembiałkowska, N; Choromańska, A; Kamińska, I; Garbiec, A; Rossowska, J; Daczewska, M; Jachimska, B; Saczko, J

    2013-11-01

    Two porphyrins, CoTPPS and MnTMPyPCl5, were tested for their photodynamic activity and potential novel use in a therapy of human cancers. We investigated an effect of photodynamic reaction (PDR), electroporation (EP) and their combination (electro-photodynamic reaction [EP-PDR]) on human colon adenocarcinoma cell lines (LoVo and resistant to doxorubicin LoVoDX), human breast adenocarcinoma (wild type MCF-7/WT and resistant to doxorubicin MCF-7/DOX), and human melanoma (Me45). The efficiency of macromolecules transport was examined with cytofluorymetry by assessing the degree of propidium iodide (PI) penetration. Additionally, cellular ultrastructure after EP was evaluated. We determined cyto- and photo-cytotoxic effect on the cells viability (MTT assay) after standard PDR and PDR combined with EP. Intracellular distribution and mitochondrial colocalization of both porphyrins was also performed. The experiments proved that both complexes exhibit desirable photodynamic properties on LoVo LoVoDX cells, and EP effectively supports photodynamic method in this type of cancer. The application of EP provided shorter time of incubation (only 10 min) and enhanced effect of applied therapy. The porphyrins did not affect the MCF-7 and Me45 cell lines.

  14. The LO Model and the Traditional French Organisational Culture: A Paradigmatic Contradiction Leading to a Limited Implementation

    ERIC Educational Resources Information Center

    Belet, Daniel

    2010-01-01

    This article deals with the issue of the very weak implementation of the LO model in France, although it appears as an appealing new management paradigm that can allow companies to better face a fast changing environment. The author argues that there is a strong philosophical contradiction between this innovative management model and the still…

  15. CXCR6 marks a novel subset of T-bet(lo)Eomes(hi) natural killer cells residing in human liver.

    PubMed

    Stegmann, Kerstin A; Robertson, Francis; Hansi, Navjyot; Gill, Upkar; Pallant, Celeste; Christophides, Theodoros; Pallett, Laura J; Peppa, Dimitra; Dunn, Claire; Fusai, Giuseppe; Male, Victoria; Davidson, Brian R; Kennedy, Patrick; Maini, Mala K

    2016-05-23

    Natural killer cells (NK) are highly enriched in the human liver, where they can regulate immunity and immunopathology. We probed them for a liver-resident subset, distinct from conventional bone-marrow-derived NK. CXCR6+ NK were strikingly enriched in healthy and diseased liver compared to blood (p < 0.0001). Human hepatic CXCR6+ NK had an immature phenotype (predominantly CD56(bright)CD16-CD57-), and expressed the tissue-residency marker CD69. CXCR6+ NK produced fewer cytotoxic mediators and pro-inflammatory cytokines than the non-liver-specific CXCR6- fraction. Instead CXCR6+ NK could upregulate TRAIL, a key death ligand in hepatitis pathogenesis. CXCR6 demarcated liver NK into two transcriptionally distinct populations: T-bet(hi)Eomes(lo)(CXCR6-) and T-bet(lo)Eomes(hi)(CXCR6+); the latter was virtually absent in the periphery. The small circulating CXCR6+ subset was predominantly T-bet(hi)Eomes(lo), suggesting its lineage was closer to CXCR6- peripheral than CXCR6+ liver NK. These data reveal a large subset of human liver-resident T-bet(lo)Eomes(hi) NK, distinguished by their surface expression of CXCR6, adapted for hepatic tolerance and inducible anti-viral immunity.

  16. CXCR6 marks a novel subset of T-bet(lo)Eomes(hi) natural killer cells residing in human liver.

    PubMed

    Stegmann, Kerstin A; Robertson, Francis; Hansi, Navjyot; Gill, Upkar; Pallant, Celeste; Christophides, Theodoros; Pallett, Laura J; Peppa, Dimitra; Dunn, Claire; Fusai, Giuseppe; Male, Victoria; Davidson, Brian R; Kennedy, Patrick; Maini, Mala K

    2016-01-01

    Natural killer cells (NK) are highly enriched in the human liver, where they can regulate immunity and immunopathology. We probed them for a liver-resident subset, distinct from conventional bone-marrow-derived NK. CXCR6+ NK were strikingly enriched in healthy and diseased liver compared to blood (p < 0.0001). Human hepatic CXCR6+ NK had an immature phenotype (predominantly CD56(bright)CD16-CD57-), and expressed the tissue-residency marker CD69. CXCR6+ NK produced fewer cytotoxic mediators and pro-inflammatory cytokines than the non-liver-specific CXCR6- fraction. Instead CXCR6+ NK could upregulate TRAIL, a key death ligand in hepatitis pathogenesis. CXCR6 demarcated liver NK into two transcriptionally distinct populations: T-bet(hi)Eomes(lo)(CXCR6-) and T-bet(lo)Eomes(hi)(CXCR6+); the latter was virtually absent in the periphery. The small circulating CXCR6+ subset was predominantly T-bet(hi)Eomes(lo), suggesting its lineage was closer to CXCR6- peripheral than CXCR6+ liver NK. These data reveal a large subset of human liver-resident T-bet(lo)Eomes(hi) NK, distinguished by their surface expression of CXCR6, adapted for hepatic tolerance and inducible anti-viral immunity. PMID:27210614

  17. High-contrast 3D image acquisition using HiLo microscopy with an electrically tunable lens

    NASA Astrophysics Data System (ADS)

    Philipp, Katrin; Smolarski, André; Fischer, Andreas; Koukourakis, Nektarios; Stürmer, Moritz; Wallrabe, Ulricke; Czarske, Jürgen

    2016-04-01

    We present a HiLo microscope with an electrically tunable lens for high-contrast three-dimensional image acquisition. HiLo microscopy combines wide field and speckled illumination images to create optically sectioned images. Additionally, the depth-of-field is not fixed, but can be adjusted between wide field and confocal-like axial resolution. We incorporate an electrically tunable lens in the HiLo microscope for axial scanning, to obtain three-dimensional data without the need of moving neither the sample nor the objective. The used adaptive lens consists of a transparent polydimethylsiloxane (PDMS) membrane into which an annular piezo bending actuator is embedded. A transparent fluid is filled between the membrane and the glass substrate. When actuated, the piezo generates a pressure in the lens which deflects the membrane and thus changes the refractive power. This technique enables a large tuning range of the refractive power between 1/f = (-24 . . . 25) 1/m. As the NA of the adaptive lens is only about 0.05, a fixed high-NA lens is included in the setup to provide high resolution. In this contribution, the scan properties and capabilities of the tunable lens in the HiLo microscope are analyzed. Eventually, exemplary measurements are presented and discussed.

  18. Nonlinear Analysis of the Space Shuttle Superlightweight LO2 Tank. Part 1; Bahavior Under Booster Ascent Loads

    NASA Technical Reports Server (NTRS)

    Young, Richard D.; Nemeth, Michael P.; Collins, Timothy J.; Starnes, James H., Jr.

    1998-01-01

    Results of linear bifurcation and nonlinear analyses of the Space Shuttle superlightweight (SLWT) external liquid-oxygen (LO2) tank for an important early booster ascent loading condition are presented. These results for thin-walled linear elastic shells that are subjected to combined mechanical and thermal loads illustrate an important type of response mode that may be encountered in the design of other liquid-fuel launch vehicles. Linear bifurcation analyses are presented that predict several nearly equal eigenvalues that correspond to local buckling modes in the forward ogive section of the LO2 tank. In contrast, the nonlinear response phenomenon is shown to consist of short-wavelength bending deformations in the forward ogive and barrel sections of the LO2 tank that growing amplitude in a stable manner increasing load. Imperfection sensitivity analyses are presented that show that the presence of several nearly equal eigenvalues does not lead to a premature general instability mode for the forward ogive section. For the linear bifurcation and nonlinear analyses, the results show that accurate predictions of the response of the shield generally require a large-scale, high-fidelity finite-element model. Results are also presented that show that the SLWT LO2 tank can support loads in excess of approximately 2.6 times the values of the operational loads considered.

  19. Mode sequence, frequency change of nonsoft phonons, and LO-TO splitting in strained tetragonal BaTiO3

    NASA Astrophysics Data System (ADS)

    Raeliarijaona, Aldo; Fu, Huaxiang

    2015-09-01

    Ultraviolet Raman spectroscopy revealed the existence of an unusual large-frequency shift occurring to a nonsoft mode of E (TO4 ) when BaTiO3 is strained to a SrTiO3 substrate [D. Tenne et al., Science 313, 1614 (2006), 10.1126/science.1130306]. It raised two interesting questions: (i) whether there are other nonsoft modes that possess similar or even larger strain-induced frequency shifts and (ii) how the mode sequence is altered by these shifts in frequency. Note that mode sequence is also pivotal in correctly indexing and assigning the spectroscopy peaks observed in all Raman experiments. By mapping out the evolutions of individual phonon modes as a function of strain using first-principles density functional perturbation calculations, we determine the mode sequence and strain-induced phonon frequency shifts in prototypical BaTiO3. Our study reveals that the mode sequence is drastically different when BaTiO3 is strained to SrTiO3 compared to that in the unstrained structure, caused by multiple mode crossings. Furthermore, we predict that three other nonsoft modes, A1(TO2), E (LO4 ), and A1(TO3), display even larger strain-induced frequency shifts than E (TO4 ). The strain responses of individual modes are found to be highly mode specific, and a mechanism that regulates the magnitude of the frequency shift is provided. As another key outcome of this study, we tackle a long-standing problem of LO-TO splitting in ferroelectrics. A rigorous definition for the LO-TO splitting is formulated, which allows this critical quantity to be calculated quantitatively. The definition immediately reveals a new finding; that is, a large LO-TO splitting not only exists for E (LO4 ), which is previously known and originates from a soft mode, it also occurs for a nonsoft A1(LO3) mode. The LO-TO splitting is shown to decrease drastically with compressive strain, and this decrease cannot be explained by the Born effective charges and high-frequency dielectric constants.

  20. STELLAR POPULATIONS AND STRUCTURAL PROPERTIES OF ULTRA FAINT DWARF GALAXIES, CANES VENATICI I, BOOeTES I, CANES VENATICI II, AND LEO IV

    SciTech Connect

    Okamoto, Sakurako; Arimoto, Nobuo; Yamada, Yoshihiko; Onodera, Masato

    2012-01-10

    We take deep images of four ultra faint dwarf (UFD) galaxies, Canes Venatici I (CVn I), Booetes I (Booe I), Canes Venatici II (CVn II), and Leo IV, using the Suprime-Cam on the Subaru Telescope. Color-magnitude diagrams (CMDs) extend below main-sequence turnoffs (MSTOs) and yield measurements of the ages of stellar populations. The stellar populations of three faint galaxies, the Booe I, CVn II, and Leo IV dwarf spheroidal galaxies (dSphs), are estimated to be as old as the Galactic globular cluster M92. We confirm that Booe I dSph has no intrinsic color spread in the MSTO and no spatial difference in the CMD morphology, which indicates that Booe I dSph is composed of an old single stellar population. One of the brightest UFDs, CVn I dSph, shows a relatively younger age ({approx}12.6 Gyr) with respect to Booe I, CVn II, and Leo IV dSphs, and the distribution of red horizontal branch (HB) stars is more concentrated toward the center than that of blue HB stars, suggesting that the galaxy contains complex stellar populations. Booe I and CVn I dSphs show the elongated and distorted shapes. CVn II dSph has the smallest tidal radius of a Milky Way satellite and has a distorted shape, while Leo IV dSph shows a less concentrated spherical shape. The simple stellar population of faint UFDs indicates that the gases in their progenitors were removed more effectively than those of brighter dSphs at the occurrence of their initial star formation. This is reasonable if the progenitors of UFDs belong to less massive halos than those of brighter dSphs.

  1. Radiation Environment at LEO in the frame of Space Monitoring Data Center at Moscow State University - recent, current and future missions

    NASA Astrophysics Data System (ADS)

    Myagkova, Irina; Kalegaev, Vladimir; Panasyuk, Mikhail; Svertilov, Sergey; Bogomolov, Vitaly; Bogomolov, Andrey; Barinova, Vera; Barinov, Oleg; Bobrovnikov, Sergey; Dolenko, Sergey; Mukhametdinova, Ludmila; Shiroky, Vladimir; Shugay, Julia

    2016-04-01

    Radiation Environment of Near-Earth space is one of the most important factors of space weather. Space Monitoring Data Center of Moscow State University provides operational control of radiation conditions at Low Earth's Orbits (LEO) of the near-Earth space using data of recent (Vernov, CORONAS series), current (Meteor-M, Electro-L series) and future (Lomonosov) space missions. Internet portal of Space Monitoring Data Center of Skobeltsyn Institute of Nuclear Physics of Lomonosov Moscow State University (SINP MSU) http://swx.sinp.msu.ru/ provides possibilities to control and analyze the space radiation conditions in the real time mode together with the geomagnetic and solar activity including hard X-ray and gamma- emission of solar flares. Operational data obtained from space missions at L1, GEO and LEO and from the Earth's magnetic stations are used to represent radiation and geomagnetic state of near-Earth environment. The models of space environment that use space measurements from different orbits were created. Interactive analysis and operational neural network forecast services are based on these models. These systems can automatically generate alerts on particle fluxes enhancements above the threshold values, both for SEP and relativistic electrons of outer Earth's radiation belt using data from GEO and LEO as input. As an example of LEO data we consider data from Vernov mission, which was launched into solar-synchronous orbit (altitude 640 - 83 0 km, inclination 98.4°, orbital period about 100 min) on July 8, 2014 and began to receive scientific information since July 20, 2014. Vernov mission have provided studies of the Earth's radiation belt relativistic electron precipitation and its possible connection with atmosphere transient luminous events, as well as the solar hard X-ray and gamma-emission measurements. Radiation and electromagnetic environment monitoring in the near-Earth Space, which is very important for space weather study, was also realised

  2. Technology Development for Human Exploration Beyond LEO in the New Millennium IAA-13-3 Strategies and Plans for Human Mars Missions

    NASA Technical Reports Server (NTRS)

    Larson, William E.; Lueck, Dale E.; Parrish, Clyde F.; Sanders, Gerald B.; Trevathan, Joseph R.; Baird, R. Scott; Simon, Tom; Peters, T.; Delgado, H. (Technical Monitor)

    2001-01-01

    As we look forward into the new millennium, the extension of human presence beyond Low-Earth Orbit (LEO) looms large in the plans of NASA. The Agency's Strategic Plan specifically calls out the need to identify and develop technologies for 100 and 1000-day class missions beyond LEO. To meet the challenge of these extended duration missions, it is important that we learn how to utilize the indigenous resources available to us on extraterrestrial bodies. This concept, known as In-Situ Resource Utilization (ISRU) can greatly reduce the launch mass & cost of human missions while reducing the risk. These technologies may also pave the way for the commercial development of space. While no specific target beyond LEO is identified in NASA's Strategic Plan, mission architecture studies have been on-going for the Moon, Mars, Near-Earth Asteroids and Earth/Moon & Earth/Sun Libration Points. As a result of these studies, the NASA Office of Space Flight (Code M) through the Johnson and Kennedy Space Centers, is leading the effort to develop ISRU technologies and systems to meet the current and future needs of human missions beyond LEO and on to Mars. This effort also receives support from the NASA Office of Biological and Physical Research (Code U), the Office of Space Science (Code S), and the Office of Aerospace Technology (Code R). This paper will present unique developments in the area of fuel and oxidizer production, breathing air production, water production, C02 collection, separation of atmospheric gases, and gas liquefaction and storage. A technology overview will be provided for each topic along with the results achieved to date, future development plans, and the mission architectures that these technologies support.

  3. Covert processing of visual form in the absence of area LO.

    PubMed

    Kentridge, R W; Heywood, C A; Milner, A D

    2004-01-01

    The patient D.F., who suffers from severe visual form agnosia, has been found to have a bilateral lesion of area LO, an area known to be intimately involved in the perception of object shape. Despite her perceptual impairment, however, D.F. retains residual form processing abilities that can provide distal visuomotor control, for example in the configuration of her grasp when reaching to pick up objects of different shapes and sizes. This dissociation has been interpreted as reflecting the sparing of a dedicated system for processing the physical properties of objects solely for purposes of guiding action. Here we test this hypothesis in two studies designed to examine whether or not spared shape processing capacities might be revealed under other kinds of indirect test conditions. First, we exploited the fact that a redundant shape cue will speed search for a coloured stimulus within an array, and vice versa. Unlike our control subjects, D.F. showed no facilitation effect of either kind. Second, we used two Stroop tasks in which single coloured uppercase letters were presented. Our intention was to determine (a) whether naming the colour would be influenced by whether the letter was the initial letter of the correct or incorrect colour name (e.g. 'R' or 'G'); and (b) whether the reverse might be true, that is that D.F.'s guesses at letter identity might be influenced by their colour. We found no evidence for a Stroop effect of the former (standard) kind in D.F., but we did find evidence for reverse-Stroop effects. This result may reflect a partial sparing of ventral stream areas specialised for letter-form processing.

  4. Spark Ignition Characteristics of a LO2/LCH4 Engine at Altitude Conditions

    NASA Technical Reports Server (NTRS)

    Kleinhenz, Julie; Sarmiento, Charles; Marshall, William

    2012-01-01

    The use of non-toxic propellants in future exploration vehicles would enable safer, more cost effective mission scenarios. One promising "green" alternative to existing hypergols is liquid methane/liquid oxygen. To demonstrate performance and prove feasibility of this propellant combination, a 100lbf LO2/LCH4 engine was developed and tested under the NASA Propulsion and Cryogenic Advanced Development (PCAD) project. Since high ignition energy is a perceived drawback of this propellant combination, a test program was performed to explore ignition performance and reliability versus delivered spark energy. The sensitivity of ignition to spark timing and repetition rate was also examined. Three different exciter units were used with the engine's augmented (torch) igniter. Propellant temperature was also varied within the liquid range. Captured waveforms indicated spark behavior in hot fire conditions was inconsistent compared to the well-behaved dry sparks (in quiescent, room air). The escalating pressure and flow environment increases spark impedance and may at some point compromise an exciter.s ability to deliver a spark. Reduced spark energies of these sparks result in more erratic ignitions and adversely affect ignition probability. The timing of the sparks relative to the pressure/flow conditions also impacted the probability of ignition. Sparks occurring early in the flow could trigger ignition with energies as low as 1-6mJ, though multiple, similarly timed sparks of 55-75mJ were required for reliable ignition. An optimum time interval for spark application and ignition coincided with propellant introduction to the igniter and engine. Shifts of ignition timing were manifested by changes in the characteristics of the resulting ignition.

  5. More food, low pollution (mo fo lo Po): a grand challenge for the 21st century.

    PubMed

    Davidson, Eric A; Suddick, Emma C; Rice, Charles W; Prokopy, Linda S

    2015-03-01

    Synthetic nitrogen fertilizer has been a double-edged sword, greatly improving human nutrition during the 20th century but also posing major human health and environmental challenges for the 21st century. In August 2013, about 160 agronomists, scientists, extension agents, crop advisors, economists, social scientists, farmers, representatives of regulatory agencies and nongovernmental organizations (NGOs), and other agricultural experts gathered to discuss the vexing challenge of how to produce more food to nourish a growing population while minimizing pollution to the environment. This collection of 14 papers authored by conference participants provides a much needed analysis of the many technical, economic, and social impediments to improving nitrogen use efficiency (NUE) in crop and animal production systems. These papers demonstrate that the goals of producing more food with low pollution (Mo Fo Lo Po) will not be achieved by technological developments alone but will also require policies that recognize the economic and social factors affecting farmer decision-making. Take-home lessons from this extraordinary interdisciplinary effort include the need (i) to develop partnerships among private and public sectors to demonstrate the most current, economically feasible, best management NUE practices at local and regional scales; (ii) to improve continuing education to private sector retailers and crop advisers; (iii) to tie nutrient management to performance-based indicators on the farm and in the downwind and downstream environment; and (iv) to restore investments in research, education, extension, and human resources that are essential for developing the interdisciplinary knowledge and innovative skills needed to achieve agricultural sustainability goals.

  6. More food, low pollution (mo fo lo Po): a grand challenge for the 21st century.

    PubMed

    Davidson, Eric A; Suddick, Emma C; Rice, Charles W; Prokopy, Linda S

    2015-03-01

    Synthetic nitrogen fertilizer has been a double-edged sword, greatly improving human nutrition during the 20th century but also posing major human health and environmental challenges for the 21st century. In August 2013, about 160 agronomists, scientists, extension agents, crop advisors, economists, social scientists, farmers, representatives of regulatory agencies and nongovernmental organizations (NGOs), and other agricultural experts gathered to discuss the vexing challenge of how to produce more food to nourish a growing population while minimizing pollution to the environment. This collection of 14 papers authored by conference participants provides a much needed analysis of the many technical, economic, and social impediments to improving nitrogen use efficiency (NUE) in crop and animal production systems. These papers demonstrate that the goals of producing more food with low pollution (Mo Fo Lo Po) will not be achieved by technological developments alone but will also require policies that recognize the economic and social factors affecting farmer decision-making. Take-home lessons from this extraordinary interdisciplinary effort include the need (i) to develop partnerships among private and public sectors to demonstrate the most current, economically feasible, best management NUE practices at local and regional scales; (ii) to improve continuing education to private sector retailers and crop advisers; (iii) to tie nutrient management to performance-based indicators on the farm and in the downwind and downstream environment; and (iv) to restore investments in research, education, extension, and human resources that are essential for developing the interdisciplinary knowledge and innovative skills needed to achieve agricultural sustainability goals. PMID:26023950

  7. Tribological characteristics of bonded MoS2 film exposed to AO, UV and real LEO environment in SM/SEED experiment

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koji; Tagawa, Masahito; Akiyama, Masao

    2009-01-01

    Influence of a ground-simulated space environment on a solid lubricant was compared to that of the real space environment. The tested lubricant that has been used for space applications was a bonded MoS2 film with organic binder. The film was irradiated individually with atomic oxygen (AO), ultraviolet rays (UV), and electron beam (EB). The fluencies of these space environment factors corresponded to exposure to the LEO environment around the International Space Station (ISS) in the Space Environment Exposure Device (SEED) experiment to about 1,2, and 3 years. Friction tests in vacuum and surface analyses were carried out for the samples. Tribological behavior of the different samples was measured using a classical reciprocating pin-on-flat friction test. Furthermore, XPS analysis of the film surface and the rubbing tracks was performed on the samples. Results show that due to AO irradiation, the friction coefficient decreased at an early stage of the tests that was similar to the results obtained on film exposed to the real LEO environment. However, no significant difference was observed with difference in AO fluence, whereas the friction coefficient of flight samples decreased concomitantly with the duration of exposure to the LEO environment.

  8. Estradiol agonists inhibit human LoVo colorectal-cancer cell proliferation and migration through p53

    PubMed Central

    Hsu, Hsi-Hsien; Kuo, Wei-Wen; Ju, Da-Tong; Yeh, Yu-Lan; Tu, Chuan-Chou; Tsai, Ying-Lan; Shen, Chia-Yao; Chang, Sheng-Huang; Chung, Li-Chin; Huang, Chih-Yang

    2014-01-01

    AIM: To investigate the effects of 17β-estradiol via estrogen receptors (ER) or direct administration of ER agonists on human colorectal cancer. METHODS: LoVo cells were established from the Bioresource Collection and Research Center and cultured in phenol red-free DMEM (Sigma, United States). To investigate the effects of E2 and/or ER selective agonists on cellular proliferation, LoVo colorectal cells were treated with E2 or ER-selective agonists for 24 h and 48 h and subjected to the MTT (Sigma) assay to find the concentration. And investigate the effects of E2 and/or ER selective agonists on cell used western immunoblotting to find out the diversification of signaling pathways. In order to observe motility and migration the wound healing assay and a transwell chamber (Neuro Probe) plate were tased. For a quantitative measure, we counted the number of migrating cells to the wound area post-wounding for 24 h. We further examined the cellular migration-regulating factors urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and matrix metalloproteinase (MMP)-9 in human LoVo cells so gelatin zymography that we used and gelatinolytic activity was visualized by Coomassie blue staining. And these results are presented as means ± SE, and statistical comparisons were made using Student’s t-test. RESULTS: The structure was first compared with E2 and ER agonists. We then treated the LoVo cells with E2 and ER agonists (10-8 mol/L) for 24 h and 48 h and subsequently measured the cell viability using MTT assay. Our results showed that treatment with 17β-estradiol and/or ER agonists in human LoVo colorectal cancer cells activated p53 and then up-regulated p21 and p27 protein levels, subsequently inhibiting the downstream target gene, cyclin D1, which regulates cell proliferation. Taken together, our findings demonstrate the anti-tumorigenesis effects of 17β-estradiol and/or ER agonists and suggest that these compounds may prove to be a

  9. Chemical characterization of milk oligosaccharides of an African lion (Panthera leo) and a clouded leopard (Neofelis nebulosa).

    PubMed

    Senda, Akitsugu; Hatakeyama, Emi; Kobayashi, Rui; Fukuda, Kenji; Uemura, Yusuke; Saito, Tadao; Packer, Craig; Oftedal, Olav T; Urashima, Tadasu

    2010-12-01

    The Carnivora include the superfamilies Canoidea and Feloidea. In species of Canoidea other than the domestic dog, Canis lupus, the milk contains only traces of lactose and much larger concentrations of oligosaccharides. In this study, lactose was found to be the dominant saccharide in the milk or colostrum of two species of Feloidea, namely the African lion (Panthera leo) and the clouded leopard (Neofelis nebulosa). In addition to lactose, the following oligosaccharides were characterized in the milk of a lion; Neu5Gc(α2-3)Gal(β1-4)Glc (3'-NGc-SL), Fuc(α1-2)Gal(β1-4)Glc (2'-fucosyllactose) and GalNAc(α1-3)[Fuc(α1-2)]Gal(β1-4)Glc (A-tetrasaccharide). The colostrum of a clouded leopard contained 3'-NGc-SL, Gal(α1-3)Gal(β1-4)Glc (isoglobotriose) and A-tetrasaccharide. These oligosaccharides differ in some respects from those previously identified in another species of Feloidea, the spotted hyena (Crocuta crocuta). These milks contained 3'-NGc-SL and A-tetrasaccharide, while spotted hyena colostrum did not; however, it contained Neu5Ac(α2-3)Gal(β1-4)Glc (3'-NAc-SL) and Gal(α1-3)[Fuc(α1-2)]Gal(β1-4)Glc (B-tetrasaccharide).

  10. The Application of Quasi-Mean-Element-Method to LEO under Additional Perturbation due to Change of Coordinate System

    NASA Astrophysics Data System (ADS)

    Tang, Jing-shi; Liu, Lin

    2010-10-01

    The perturbation caused by the oscillation of Earth's equator plane must be taken into account when working on the motion of satellite on a low Earth orbit (LEO) in the geocentric celestial coordinate system. Since 1960 s, an intermediate orbit coordinate system using true equator and mean equinox (TEME) is introduced. It effectively solves the problem and has been widely used in various applications till today. But this traditional reference frame is purely conceptual and has always been a headache when performing the transition between these systems especially for those who are unfamiliar with celestial frames. As proved in a previous paper, it is possible to avoid the intermediate TEME frame, and conversions between osculating elements and mean elements can be completed in a consistent geocentric celestial coordinate system where only short-period terms are required. In this paper, after including the improved secular and long-period terms, the quasi-mean-element-method is available to predict the orbit analytically, reaching the accuracy of 10 -6 in Earth's radius. And all these can be done in the same celestial frame. The results suggest that the celestial coordinate system (J2000.0 nowadays) can be used throughout any applications without having to introduce TEME system as intermediate frame any more.

  11. Accumulation of perfluorinated compounds in captive Bengal tigers (Panthera tigris tigris) and African lions (Panthera leo Linnaeus) in China.

    PubMed

    Li, Xuemei; Yeung, Leo Wai Yin; Taniyasu, Sachi; Lam, Paul K S; Yamashita, Nobuyoshi; Xu, Muqi; Dai, Jiayin

    2008-11-01

    The accumulation of perfluorinated compounds (PFCs) in the sera of captive wildlife species Bengal tigers (Panthera tigris tigris) and African lions (Panthera leo Linnaeus) from Harbin Wildlife Park, Heilongjiang Province, in China were analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Perfluorooctanesulfonate (PFOS) was the predominant contaminant with a mean serum concentration of 1.18 ng mL(-1) in tigers and 2.69 ng mL(-1) in lions. Perfluorononanoic acid (PFNA) was the second most prevalent contaminant in both species. The composition profiles of the tested PFCs differed between tigers and lions, and the percentages of perfluorooctanoic acid (PFOA) were greater in lions than in tigers, indicating different exposures and/or metabolic capabilities between the two species. Assessments of the risk of PFC contamination to the two species were obtained by comparing measured concentrations to points of departure or toxicity reference values (TRVs). Results suggest no risk of PFOS exposure or toxicity for the two species.

  12. Space Radiation Environment Prediction for VLSI microelectronics devices onboard a LEO Satellite using OMERE-Trad Software

    NASA Astrophysics Data System (ADS)

    Sajid, Muhammad

    This tutorial/survey paper presents the assessment/determination of level of hazard/threat to emerging microelectronics devices in Low Earth Orbit (LEO) space radiation environment with perigee at 300 Km, apogee at 600Km altitude having different orbital inclinations to predict the reliability of onboard Bulk Built-In Current Sensor (BBICS) fabricated in 350nm technology node at OptMA Lab. UFMG Brazil. In this context, the various parameters for space radiation environment have been analyzed to characterize the ionizing radiation environment effects on proposed BBICS. The Space radiation environment has been modeled in the form of particles trapped in Van-Allen radiation belts(RBs), Energetic Solar Particles Events (ESPE) and Galactic Cosmic Rays (GCR) where as its potential effects on Device- Under-Test (DUT) has been predicted in terms of Total Ionizing Dose (TID), Single-Event Effects (SEE) and Displacement Damage Dose (DDD). Finally, the required mitigation techniques including necessary shielding requirements to avoid undesirable effects of radiation environment at device level has been estimated /determined with assumed standard thickness of Aluminum shielding. In order to evaluate space radiation environment and analyze energetic particles effects on BBICS, OMERE toolkit developed by TRAD was utilized.

  13. Phylogeography of lions (Panthera leo ssp.) reveals three distinct taxa and a late Pleistocene reduction in genetic diversity.

    PubMed

    Barnett, Ross; Shapiro, Beth; Barnes, Ian; Ho, Simon Y W; Burger, Joachim; Yamaguchi, Nobuyuki; Higham, Thomas F G; Wheeler, H Todd; Rosendahl, Wilfried; Sher, Andrei V; Sotnikova, Marina; Kuznetsova, Tatiana; Baryshnikov, Gennady F; Martin, Larry D; Harington, C Richard; Burns, James A; Cooper, Alan

    2009-04-01

    Lions were the most widespread carnivores in the late Pleistocene, ranging from southern Africa to the southern USA, but little is known about the evolutionary relationships among these Pleistocene populations or the dynamics that led to their extinction. Using ancient DNA techniques, we obtained mitochondrial sequences from 52 individuals sampled across the present and former range of lions. Phylogenetic analysis revealed three distinct clusters: (i) modern lions, Panthera leo; (ii) extinct Pleistocene cave lions, which formed a homogeneous population extending from Europe across Beringia (Siberia, Alaska and western Canada); and (iii) extinct American lions, which formed a separate population south of the Pleistocene ice sheets. The American lion appears to have become genetically isolated around 340 000 years ago, despite the apparent lack of significant barriers to gene flow with Beringian populations through much of the late Pleistocene. We found potential evidence of a severe population bottleneck in the cave lion during the previous interstadial, sometime after 48 000 years, adding to evidence from bison, mammoths, horses and brown bears that megafaunal populations underwent major genetic alterations throughout the last interstadial, potentially presaging the processes involved in the subsequent end-Pleistocene mass extinctions. PMID:19302360

  14. The Power of Wide Field HI Surveys: ALFALFA Imaging of Massive Tidal Features in the Leo Cloud of Galaxies

    NASA Astrophysics Data System (ADS)

    Leisman, Luke; Haynes, Martha P.; Giovanelli, Riccardo; ALFALFA Almost Darks Team

    2016-01-01

    Tidal interactions are well known to play an important role in galactic evolution in group environments, but the extent of these interactions, and their relative impact on the morphology-density relation is still unclear. Neutral hydrogen (HI) mapping can reveal the recent interaction history of group galaxies, but is difficult to execute due to the need for high sensitivity over wide fields. The Arecibo Legacy Fast ALFA survey (ALFALFA; Giovanelli et al. 2005; Haynes et al. 2011) provides high sensitivity, unbiased, wide field maps of HI in the local volume; here we will present a 50 deg2 ALFALFA map of a well studied region of the Leo Cloud of galaxies, which includes the NGC3226/7 group and HCG44. These observations reveal HI tails and plumes with extents exceeding 1.4 deg (~600 kpc), well beyond the primary beams of previous observations. These tails constitute a significant fraction of the total HI mass in NGC3226/7 (Arp 94) and HCG44. We will also present WSRT maps of the extended emission near Arp 94, which show tail morphologies inconsistent with 2 body interactions. These observations demonstrate that large scale group interactions will be an important science outcome for future sensitive, wide field HI surveys.This work is supported by NSF grants AST-0607007 and AST-1107390 and by grants from the Brinson Foundation.

  15. Spacecraft-plasma interaction codes: NASCAP/GEO, NASCAP/LEO, POLAR, DynaPAC, and EPSAT

    NASA Technical Reports Server (NTRS)

    Mandell, M. J.; Jongeward, G. A.; Cooke, D. L.

    1992-01-01

    Development of a computer code to simulate interactions between the surfaces of a geometrically complex spacecraft and the space plasma environment involves: (1) defining the relevant physical phenomena and formulating them in appropriate levels of approximation; (2) defining a representation for the 3-D space external to the spacecraft and a means for defining the spacecraft surface geometry and embedding it in the surrounding space; (3) packaging the code so that it is easy and practical to use, interpret, and present the results; and (4) validating the code by continual comparison with theoretical models, ground test data, and spaceflight experiments. The physical content, geometrical capabilities, and application of five S-CUBED developed spacecraft plasma interaction codes are discussed. The NASA Charging Analyzer Program/geosynchronous earth orbit (NASCAP/GEO) is used to illustrate the role of electrostatic barrier formation in daylight spacecraft charging. NASCAP/low Earth orbit (LEO) applications to the CHARGE-2 and Space Power Experiment Aboard Rockets (SPEAR)-1 rocket payloads are shown. DynaPAC application to the SPEAR-2 rocket payloads is described. Environment Power System Analysis Tool (EPSAT) is illustrated by application to Tethered Satellite System 1 (TSS-1), SPEAR-3, and Sundance. A detailed description and application of the Potentials of Large Objects in the Auroral Region (POLAR) Code are presented.

  16. Changes in the composition, structure and friction property of sputtered MoS2 films by LEO environment exposure

    NASA Astrophysics Data System (ADS)

    Gao, Xiaoming; Hu, Ming; Sun, Jiayi; Fu, Yanlong; Yang, Jun; Liu, Weimin; Weng, Lijun

    2015-03-01

    Radio frequency-sputtered MoS2 films had been exposed for 43.5 h in real low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard China Shenzhou-7 manned spaceship. The composition, morphology, phase structure and friction property of the exposed films were investigated using X-ray photoelectron spectroscope (XPS), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray energy-dispersive spectroscopy (EDS) and ball-on-disk tribometer. XRD and EDS results revealed that the as-deposited MoS2 films were characterized by a MoSxOy phase structure, in which x and y values were determined to be ∼0.65 and 1.24, respectively. XPS analysis revealed that due to space atomic oxygen attack, the film surface was oxidized to MoO3 and MoSxOy with higher O concentration, while the partial S was lost. However, the affected depth was restricted within the surface layer because of protective function of the oxidation layer. As a result, the friction coefficient only exhibited a slight increase at initial stage of sliding friction.

  17. Understanding Societies from Inside the Organisms. Leo Pardi's Work on Social Dominance in Polistes Wasps (1937-1952).

    PubMed

    Caniglia, Guido

    2015-08-01

    Leo Pardi (1915-1990) was the initiator of ethological research in Italy. During more than 50 years of active scientific career, he gave groundbreaking contributions to the understanding of social life in insects, especially in Polistes wasps, an important model organism in sociobiology. In the 1940s, Pardi showed that Polistes societies are organized in a linear social hierarchy that relies on reproductive dominance and on the physiological and developmental mechanisms that regulate it, i.e. on the status of ovarian development of single wasps. Pardi's work set the stage for further research on the regulatory mechanisms governing social life in primitively eusocial organisms both in wasps and in other insect species. This article reconstructs Pardi's investigative pathway between 1937 and 1952 in the context of European ethology and American animal sociology. This reconstruction focuses on the development of Pardi's physiological approach and presents a new perspective on the interacting development of these two fields at the origins of our current understanding of animal social behavior.

  18. Pristine and Surface-Modified Polymers in LEO: MISSE Results versus Predictive Models and Ground-Based Testing

    NASA Astrophysics Data System (ADS)

    Iskanderova, Zelina; Kleiman, Jacob I.; Tennyson, Rod C.

    2009-01-01

    Space flight data, collected and published by NASA Glenn Research Center (GRC) team for a set of pristine polymeric materials selected, compiled, and tested in two LEO flight experiments at the International Space Station, as part of the "Materials International Space Station Experiment" (MISSE), has been used for comparison with previously developed atomic oxygen erosion predictive models. The same set of materials was used for a ground-based fast atomic beam (FAO) experimental erosion study at ITL/UTIAS, where the FAO exposure was performed mostly at a standard fluence of 2×1020 cm-2, with the results collected in a database for the development of a prototype of predictive software. A comparison of MISSE-1 flight data with two predictive correlations has shown good agreement, confirming the developed approach to polymers erosion resistance forecast that might be used also for newly developed or untested in space polymeric materials. A number of surface-modified thin film space polymers, treated by two ITL-developed and patented surface modification technologies, Implantox™ [5] and Photosil™ [6], have been also included in MISSE flight experiment. The results from those MISSE samples have shown full protection of AO-sensitive main space-related hydrocarbon polymers, such as Kapton HN, back-metalized Kapton H and Kapton E, and Mylar, when treated by Implantox™ surface modification technology and significant erosion resistance enhancement up to full protection by Photosil™ treatment.

  19. HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: LEO IV

    SciTech Connect

    Simon, Joshua D.; McWilliam, Andrew; Thompson, Ian B.; Frebel, Anna; Kirby, Evan N. E-mail: andy@ociw.ed E-mail: afrebel@cfa.harvard.ed

    2010-06-10

    We present high-resolution Magellan/MIKE spectroscopy of the brightest star in the ultra-faint dwarf galaxy Leo IV. We measure an iron abundance of [Fe/H] = -3.2, adding to the rapidly growing sample of extremely metal-poor (EMP) stars being identified in Milky Way satellite galaxies. The star is enhanced in the {alpha} elements Mg, Ca, and Ti by {approx}0.3 dex, very similar to the typical Milky Way halo abundance pattern. All of the light and iron-peak elements follow the trends established by EMP halo stars, but the neutron-capture elements Ba and Sr are significantly underabundant. These results are quite similar to those found for stars in the ultra-faint dwarfs Ursa Major II, Coma Berenices, Booetes I, and Hercules, suggesting that the chemical evolution of the lowest-luminosity galaxies may be universal. The abundance pattern we observe is consistent with predictions for nucleosynthesis from a Population III supernova explosion. The extremely low metallicity of this star also supports the idea that a significant fraction ({approx}>10%) of the stars in the faintest dwarfs have metallicities below [Fe/H] = -3.0.

  20. Accumulation of perfluorinated compounds in captive Bengal tigers (Panthera tigris tigris) and African lions (Panthera leo Linnaeus) in China.

    PubMed

    Li, Xuemei; Yeung, Leo Wai Yin; Taniyasu, Sachi; Lam, Paul K S; Yamashita, Nobuyoshi; Xu, Muqi; Dai, Jiayin

    2008-11-01

    The accumulation of perfluorinated compounds (PFCs) in the sera of captive wildlife species Bengal tigers (Panthera tigris tigris) and African lions (Panthera leo Linnaeus) from Harbin Wildlife Park, Heilongjiang Province, in China were analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Perfluorooctanesulfonate (PFOS) was the predominant contaminant with a mean serum concentration of 1.18 ng mL(-1) in tigers and 2.69 ng mL(-1) in lions. Perfluorononanoic acid (PFNA) was the second most prevalent contaminant in both species. The composition profiles of the tested PFCs differed between tigers and lions, and the percentages of perfluorooctanoic acid (PFOA) were greater in lions than in tigers, indicating different exposures and/or metabolic capabilities between the two species. Assessments of the risk of PFC contamination to the two species were obtained by comparing measured concentrations to points of departure or toxicity reference values (TRVs). Results suggest no risk of PFOS exposure or toxicity for the two species. PMID:18789477

  1. Volatile organic compound fluxes and concentrations in London (ClearfLo)

    NASA Astrophysics Data System (ADS)

    Valach, Amy; Langford, Ben; Nemitz, Eiko; MacKenzie, Rob; Hewitt, Nick

    2014-05-01

    Volatile organic compounds (VOCs) from anthropogenic sources such as fuel combustion or evaporative emissions can directly and indirectly affect human health. Some VOCs, such as benzene and 1,3- butadiene are carcinogens. These and other VOCs contribute to the formation of ozone (O3) and aerosol particles, which have effects on human health and the radiative balance of the atmosphere. Although in the UK VOC emissions are subject to control under European Commission Directive 2008/50/EC and emission reducing technologies have been implemented, urban air pollution remains a concern. Urban air quality is likely to remain a priority since currently >50% of the global population live in urban areas with trends in urbanization and population migration predicted to increase. The ClearfLo project is a large multi-institutional consortium funded by the UK Natural Environment Research Council (NERC) and provides integrated measurements of meteorology, gas phase and particulate composition of the atmosphere over London. Both long term and IOP measurements were made at street and elevated locations at a range of sites across London and its surroundings during 2011 and 2012. Mixing ratios of a selection of nine VOCs were measured using a high sensitivity proton transfer reaction-mass spectrometer (PTR-MS) at a ground level urban background (North Kensington) and kerbside (Marylebone Road) site during the winter IOP. VOC fluxes were measured by virtually disjunct eddy covariance (vDEC) at an elevated urban site (King's College Strand) in Aug-Dec 2012. Our results for the first IOP showed that most of the selected compound concentrations depended on traffic emissions, although there was a marked difference between the urban background and kerbside sites. We identified some temperature effects on VOC concentrations. We also present the first analyses of VOC flux measurements over London. Preliminary analyses indicate most compounds associated with vehicle emissions closely

  2. Cytotoxicity of lymphocytes activated by superantigen toxic-shock-syndrome toxin-1 against colorectal cancer LoVo cells.

    PubMed

    Wang, Wei; Sun, Xuejun; Lu, Le; Zheng, Jian-Bao; Tian, Yong; Wang, Wei

    2013-04-01

    Toxic-shock-syndrome toxin-1 (TSST-1), a superantigen, can stimulate T cell activation and be used for immunotherapy. In this study, we employed the carcinoembryonic antigen (CEA)-positive LoVo cells to test whether retrovirus-mediated TSST-1 expression could activate human T cells and promote cytotoxicity against tumor cells. We first generated plasmids of pLEGFP-N1-5HRE-CEAp-TSST-1-linker-CD80TM containing a fusion gene of the CEA promoter, 5 copies of the hypoxia-response elements (HRE) as an enhancer, the fragments for TSST-1, and the transmembrane domain of CD80 (CD80TM) and control pLEGFP-N1-5HRE-CEAp (without TSST-1) and generated retroviruses of 5HCTC and 5HC, respectively. After infection with 5HC and 5HCTC retroviruses to establish cell lines, the high levels of TSST-1 expression were observed on the membrane and cytoplasm of the 5HCTC-infected LoVo cells, particularly culture under a hypoxic condition, but not on CEA(-) HeLa cells. Furthermore, the TSST-1-expressing LoVo cell lysates, but not the control cell lysates, stimulated human T cell proliferation, and the co-culture of the TSST-1-expressing LoVo, but not control cells, with human peripheral blood mononuclear cells (PBMC) induced a high frequency of TNF-α- and IL-2-secreting T cells in vitro, particularly under hypoxic conditions. More importantly, co-culture of the TSST-1-expressing LoVo cells, particularly under hypoxic conditions, but not control cells, with different numbers of PBMC promoted potent cytotoxicity against LoVo cells in a dose-dependent manner in vitro. These data provide proof of the principle that selective induction of TSST1 expression in CEA(+) colorectal cancer (CRC) cells activates T cells that destroy tumor cells, particularly under a hypoxic condition. Therefore, our findings may aid in the design of new immunotherapy for the intervention of CRC at clinic.

  3. Effect of RNAi-mediated silencing of Livin gene on biological properties of colon cancer cell line LoVo.

    PubMed

    Zou, A M; Wang, H F; Zhu, W F; Wang, F X; Shen, J J

    2014-05-16

    This study aimed to investigate the effect of RNAi-mediated silencing of the Livin gene on biological properties of the colon cancer cell line LoVo. Interference vectors pSilencer4.1-Ll and pSilencer4.1-L2 targeting the Livin gene were constructed and transfected into LoVo cells. The expression of the Livin gene was determined by RT-PCR and Western blotting. The apoptosis, cell cycle, colony formation, proliferation of LoVo cells, as well as their sensitivity to cisplatin, were detected by flow cytometry, colony formation assay and MTT. Livin mRNA and protein expression in LoVo cells could be effectively silenced by pSilencer4.1-Ll but not pSilencer4.1-L2. In the pSilencer4.1-Ll transfection group, the apoptosis rate of LoVo cells was significantly higher than in the control group (24.2 ± 3.2 vs 8.1 ± 1.4%, P < 0.01), and after 72 h, cell proliferation was clearly decreased (about 70% inhibition). Compared with the control group, the colony formation rate in pSilencer4.1-Ll transfection group was obviously decreased (15 ± 4.6 vs 85 ± 5.8%, P < 0.01), with increased proportion of S phase cells (45.7 ± 4.9 vs 28.0 ± 3.0%, P < 0.01), decreased proportion of G1 phase cells (43.0 ± 5.2 vs 62.8 ± 5.1%, P < 0.01), and increased sensitivity to cisplatin (apoptosis rate increased from 43.4 ± 6.9 to 65.3 ± 6.2%, P < 0.01). pSilencer4.1-Ll can effectively silence Livin gene expression in LoVo colon cancer cells, inhibit cell proliferation and colony formation, induce apoptosis, and enhance sensitivity to cisplatin.

  4. 100-Lb(f) LO2/LCH4 Reaction Control Engine Technology Development for Future Space Vehicles

    NASA Technical Reports Server (NTRS)

    Robinson, Philip J.; Veith, Eric M.; Hurlbert, Eric A.; Jimenez, Rafael; Smith, Timothy D.

    2008-01-01

    The National Aeronautics and Space Administration (NASA) has identified liquid oxygen (LO2)/liquid methane (LCH4) propulsion systems as promising options for some future space vehicles. NASA issued a contract to Aerojet to develop a 100-lbf (445 N) LO2/LCH4 Reaction Control Engine (RCE) aimed at reducing the risk of utilizing a cryogenic reaction control system (RCS) on a space vehicle. Aerojet utilized innovative design solutions to develop an RCE that can ignite reliably over a broad range of inlet temperatures, perform short minimum impulse bits (MIB) at small electrical pulse widths (EPW), and produce excellent specific impulse (Isp) across a range of engine mixture ratios (MR). These design innovations also provide a start transient with a benign MR, ensuring good thrust chamber compatibility and long life. In addition, this RCE can successfully operate at MRs associated with main engines, enabling the RCE to provide emergency backup propulsion to minimize vehicle propellant load and overall system mass.

  5. LO phonons in La{sub 1.85}Sr{sub .15}CuO{sub 4}

    SciTech Connect

    Egami, T.; Petrov, Y.; McQueeney, R.J.; Petrov, Y.; Yethiraj, M.; Shirane, G.; Endoh, Y.

    1997-11-01

    Dispersion of the highest energy LO phonons in La{sup 1.85}Sr{sub .15}CuO{sub 4} was studied by neutron inelastic scattering. At T = 10 K the dispersion along (h, 0, 0) is anomalous forming dispersion branches with a discontinuity at h = 1/4. A possible relation of this anomaly to the spin-charge stripes with be discussed.

  6. Design, Calibration, and Expected On-Orbit Performance of the GOES-R MPS-LO Suprathermal Plasma Analyzer Instrument

    NASA Astrophysics Data System (ADS)

    Golightly, M. J.; McGarity, J. O.; Dichter, B. K.; Galica, G. E.

    2015-12-01

    The next generation U.S. geosynchronous weather satellite—GOES series R-U—will include for the first time a suprathermal plasma analyzer. The Magnetospheric Particle Sensor-Low (MPS-LO), an electrostatic analyzer utilizing triquadrispheric geometry (270° turn)deflection electrodes, will measure the flux of electrons and ions with energies between 30 eV - 30 keV in fifteen logarithmically-spaced differential energy channels and arrival direction in twelve angular bins. MPS-LO consists of two sensor heads mounted in a common electronics box. Each sensor head contains a set of deflection electrodes, microchannel plates, and segmented detector anodes. The common electronics box provides the power and I/O interface with a data processing unit, voltage supplies for all of the instrument's electronics, high voltage for the deflection electrodes, in-flight calibration pulsers, and the digital electronics to process signals from sensor heads' detector anodes. Great care was taken in the manufacture and mounting of the triquadrisphere deflection electrodes; each electrode was machined from a single piece of aluminum and specific electrode combinations were mounted with precision machined spacers and matched drilling. The precise fabrication and assembly resulted in near perfect spherical electric fields between the electrodes. The triquadrispheric electrode shape also prevents photons from reaching the detection elements-as a result, MPS-LO is solar blind. The combined field-of-view for the two sensor heads is 180° x 5°, with the larger angle in a plane perpendicular to the spacecraft's orbit and its central axis oriented anti-Earthward. An incident particle's arrival direction is determined in one of twelve 15° x 5° angular zones. A set of shielded anodes is used to measure the background caused by penetrating charged particles that reach the MCPs; this background data is used to correct the MPS-LO data. The instrument's energy resolution ΔE/E is 5.8%.

  7. Enhancement of the HIF-1α/15-LO/15-HETE Axis Promotes Hypoxia-Induced Endothelial Proliferation in Preeclamptic Pregnancy

    PubMed Central

    Liu, Qian; Zhang, Yanhua; Li, Huiying; Li, Peiling; Zhu, Daling

    2014-01-01

    Preeclampsia (PE) is an extremely serious condition in pregnant women and the leading cause of maternal and fetal morbidity and mortality. Despite active research, the etiological factors of this disorder remain elusive. The increased release of 15-hydroxyeicosatetraenoic acid (15-HETE) in the placenta of preeclamptic patients has been studied, but its exact role in PE pathogenesis remains unknown. Mounting evidence shows that PE is associated with placental hypoxia, impaired placental angiogenesis, and endothelial dysfunction. In this study, we confirmed the upregulated expression of hypoxia-inducible factor 1α (HIF-1α) and 15-lipoxygenase-1/2 (15-LO-1/2) in patients with PE. Production of the arachidonic acid metabolite, 15-HETE, also increased in the preeclamptic placenta, which suggests enhanced activation of the HIF-1α–15-LO–15-HETE axis. Furthermore, this study is the first to show that the umbilical cord of preeclamptic women contains significantly higher serum concentrations of 15-HETE than that of healthy pregnant women. The results also show that expression of 15-LO-1/2 is upregulated in both human umbilical vein endothelial cells (HUVECs) collected from preeclamptic women and in those cultured under hypoxic conditions. Exogenous 15-HETE promotes the migration of HUVECs and in vitro tube formation and promotes cell cycle progression from the G0/G1 phase to the G2/M + S phase, whereas the 15-LO inhibitor, NDGA, suppresses these effects. The HIF-1α/15-LO/15-HETE pathway is therefore significantly associated within the pathology of PE. PMID:24796548

  8. A Study of the Relationship between Levels of Technology Implementation (LoTi) and Student Performance on Texas Assessment of Knowledge and Skills (TAKS) Scores

    ERIC Educational Resources Information Center

    Berkeley-Jones, Catherine Spotswood

    2012-01-01

    The purpose of this study was to examine teacher Levels of Technology Implementation (LoTi) self-ratings and student Texas Assessment of Knowledge and Skills (TAKS) scores. The study assessed the relationship between LoTi ratings and TAKS scores of 6th, 7th, and 8th grade students as reported in student records at Alamo Heights Independent School…

  9. Comments on Virginia LoCastro's "Learning Strategies and Learning Environments." Making Sense of Learning Strategy Assessment: Toward a Higher Standard of Research Accuracy.

    ERIC Educational Resources Information Center

    Oxford, Rebecca L.; Green, John M.

    1995-01-01

    Critiques an article by Virginia LoCastro that contrasted quantitative data (using the Strategy Inventory for Language Learning, or SILL) and qualitative data (using group interviews) and finds the conclusions drawn from the comparison unjustified on various grounds. A reply by LoCastro is included. (Contains a combined total of 20 references.)…

  10. Lava bubble-wall fragments formed by submarine hydrovolcanic explosions on Lo'ihi Seamount and Kilauea Volcano

    USGS Publications Warehouse

    Clague, D.A.; Davis, A.S.; Bischoff, J.L.; Dixon, J.E.; Geyer, R.

    2000-01-01

    Glassy bubble-wall fragments, morphologically similar to littoral limu o Pele, have been found in volcanic sands erupted on Lo'ihi Seamount and along the submarine east rift zone of Kilauea Volcano. The limu o Pele fragments are undegassed with respect to H2O and S and formed by mild steam explosions. Angular glass sand fragments apparently form at similar, and greater, depths by cooling-contraction granulation. The limu o Pele fragments from Lo'ihi Seamount are dominantly tholeiitic basalt containing 6.25-7.25% MgO. None of the limu o Pele samples from Lo'ihi Seamount contains less than 5.57% MgO, suggesting that higher viscosity magmas do not form lava bubbles. The dissolved CO2 and H2O contents of 7 of the limu o Pele fragments indicate eruption at 1200??300 m depth (120??30 bar). These pressures exceed that generally thought to limit steam explosions. We conclude that hydrovolcanic eruptions are possible, with appropriate pre-mixing conditions, at pressures as great as 120 bar.

  11. Matrine inhibits proliferation and induces apoptosis of human colon cancer LoVo cells by inactivating Akt pathway.

    PubMed

    Zhang, Shujun; Cheng, Binglin; Li, Hali; Xu, Wei; Zhai, Bo; Pan, Shangha; Wang, Lei; Liu, Ming; Sun, Xueying

    2014-01-01

    The present study has investigated the anti-tumor activity and the underlying mechanisms of matrine on human colon cancer LoVo cells. Matrine inhibited the proliferation of the cells in dose- and time-dependent manners. The concentration required for 50 % inhibition (IC50) was 1.15, 0.738, and 0.414 mg/ml, when cell were incubated with matrine for 24, 48, and 72 h, respectively. Matrine induced cell cycle arrest at G1 phase by downregulating cyclin D1 and upregulating p27 and p21. Matrine induced cell apoptosis by reducing the ratio of Bcl-2/Bax and increasing the activation of caspase-9 in a dose-dependent manner. Matrine displayed its anti-tumor activity by inactivating Akt, the upstream factor of the above proteins. Matrine significantly reduced the protein levels of pAkt, and increased the protein levels of other downstream factors, pBad and pGSK-3β. Specific inhibition of pAkt induced cell apoptosis, and synergized with matrine to inhibit the proliferation of LoVo cells; whereas activation of Akt neutralized the inhibitory effect of matrine on cell proliferation. The present study has demonstrated that matrine inhibits proliferation and induces apoptosis of human colon cancer LoVo cells by inactivating Akt pathway, indicating matrine may be a potential anti-cancer agent for colon cancer.

  12. Effects of paeonol on intracellular calcium concentration and expression of RUNX3 in LoVo human colon cancer cells.

    PubMed

    Li, Ming; Tan, Shi-Yun; Zhang, Jun; You, Hong-Xia

    2013-05-01

    Paeonol, a major phenolic component of the root bark of Paeonia moutan, is known to exhibit antitumor effects. However, the underlying mechanisms remain unknown. In the present study, the effects of paeonol on cell viability, intracellular calcium concentration and the expression of runt‑related transcription factor 3 (RUNX3) were analyzed in LoVo human colon cancer cells. Results revealed that paeonol markedly reduced LoVo cell viability in a time‑ and dose‑dependent manner. Flow cytometry assays demonstrated that paeonol blocked the cell cycle at the G1 to S transition and significantly induced apoptosis in LoVo cells. Intracellular calcium accumulation occurred following a 48 h treatment with paeonol. Furthermore, RUNX3 gene expression was increased in paeonol‑treated cells. These observations indicate that paeonol possesses antiproliferative properties and apoptosis‑inducing activity. One of the antitumor mechanisms of paeonol may be its apoptosis‑inducing activity through an increased intracellular calcium concentration and the upregulation of RUNX3 expression. Paeonol may be a promising antitumor agent for colon carcinoma treatment.

  13. Analyzing the interstellar neutral He bulk flow parameters with IBEX-Lo

    NASA Astrophysics Data System (ADS)

    Leonard, Trevor W.

    Our Sun is immersed in a local galactic environment which is composed of a warm, dilute, and partially ionized gas. Due to the Sun's motion relative to this environment, the interstellar neutral (ISN) gas flows through the heliosphere providing the opportunity to perform in-situ observations of the ISN gas from Earth's orbit. The Interstellar Boundary Explorer (IBEX) has observed the ISN gas flow over the past 7 years from a highly elliptical orbit around the Earth. The first observations of ISN H, O, and Ne were recorded by IBEX, along with the most detailed observation of ISN He. Since He is minimally influenced by ionization and charge exchange, the ISN He flow provides a sample of the pristine interstellar environment. Surprisingly, the analysis of the early IBEX observations of the ISN He flow in 2009 and 2010 with two separate analysis techniques indicated a somewhat different ISN He parameter set than the previous neutral gas observations with Ulysses GAS. One analysis technique employs the Warsaw Test Particle Model (WTPM) to simulate the ISN atom trajectories numerically from the observer position to the boundary of the heliosphere at 150 AU with spatial and temporal dependent ionization rates. A computational intensive global chi-squared minimization of the WTPM to IBEX-Lo observations is performed to characterize the ISN He flow. The second analysis technique, and the subject of this study, takes advantage of simplifications possible due to the IBEX viewing geometry of ISN atoms close to perihelion in their hyperbolic trajectories. The analytical model is based on Liouville's Theorem with the assumption that the ISN He distribution is a drifting Maxwellian in the local interstellar medium. The analytical model is used to make a 3-step approach to determining the ISN He flow vector and temperature, rather than a global chi-squared minimization. The first step determines the location of the peak ISN He flux at Earth orbit to fix the relationship between

  14. A technique for synergistic atomic oxygen and vacuum ultraviolet radiation durability evaluation of materials for use in LEO

    NASA Technical Reports Server (NTRS)

    Rutledge, Sharon K.; Banks, Bruce A.

    1996-01-01

    Material erosion data collected during flight experiments such as the Environmental Oxygen Interaction with Materials (EOIM)-3 and the Long Duration Exposure Facility (LDEF) have raised questions as to the sensitivity of material erosion to levels of atomic oxygen exposure and vacuum ultraviolet (VUV) radiation. The erosion sensitivity of some materials such as FEP Teflon used as a thermal control material on satellites in low Earth orbit (LEO), is particularly important but difficult to determine. This is in large part due to the inability to hold all but one exposure parameter constant during a flight experiment. This is also difficult to perform in a ground based facility, because often the variation of the level of atomic oxygen or VUV radiation also results in a change in the level of the other parameter. A facility has been developed which allows each parameter to be changed almost independently and offer broad area exposure. The resulting samples can be made large enough for mechanical testing. The facility uses an electron cyclotron resonance plasma source to provide the atomic oxygen. A series of glass plates is used to focus the atomic oxygen while filtering the VUV radiation from the plasma source. After filtering, atomic oxygen effective flux levels can still be measured which are as high as 7 x 10(exp 15) atoms/cm(exp 2)-sec which is adequate for accelerated testing. VUV radiation levels after filtering can be as low as 0.3 suns. Additional VUV suns can be added with the use of deuterium lamps which allow the VUV level to be changed while keeping the flux of atomic oxygen constant. This paper discusses the facility, and results from exposure of Kapton and FEP at pre-determined atomic oxygen flux and VUV sun levels.

  15. Estimated performance and future potential of solar dynamic and photovoltaic power systems for selected LEO and HEO missions

    NASA Technical Reports Server (NTRS)

    Bents, David J.; Lu, Cheng Y.

    1989-01-01

    Solar Photo Voltaic (PV) and thermal dynamic power systems for application to selected Low Earth Orbit (LEO) and High Eccentric Orbit (Energy) (HEO) missions are characterized in the regime 7 to 35 kWe. Input parameters to the characterization are varied corresponding to anticipated introduction of improved or new technologies. Comparative assessment is made between the two power system types utilizing newly emerging technologies in cells and arrays, energy storage, optical surfaces, heat engines, thermal energy storage, and thermal management. The assessment is made to common ground rules and assumptions. The four missions (space station, sun-synchronous, Van Allen belt and GEO) are representative of the anticipated range of multi-kWe earth orbit missions. System characterizations include all required subsystems, including power conditioning, cabling, structure, to deliver electrical power to the user. Performance is estimated on the basis of three different levels of component technology: (1) state-of-art, (2) near-term, and (3) advanced technologies. These range from planar array silicon/IPV nickel hydrogen batteries and Brayton systems at 1000 K to thin film GaAs with high energy density secondary batteries or regenerative fuel cells and 1300 K Stirling systems with ultra-lightweight concentrators and radiators. The system estimates include design margin for performance degradations from the known environmental mechanisms (micrometeoroids and space debris, atomic oxygen, electron and proton flux) which are modeled and applied depending on the mission. The results give expected performance, mass and drag of multi-kWe earth orbiting solar power systems and show how overall system figures of merit will improve as new component technologies are incorporated.

  16. Lion (Panthera leo) and caracal (Caracal caracal) type IIx single muscle fibre force and power exceed that of trained humans.

    PubMed

    Kohn, Tertius A; Noakes, Timothy D

    2013-03-15

    This study investigated for the first time maximum force production, shortening velocity (Vmax) and power output in permeabilised single muscle fibres at 12°C from lion, Panthera leo (Linnaeus 1758), and caracal, Caracal caracal (Schreber 1776), and compared the values with those from human cyclists. Additionally, the use and validation of previously frozen tissue for contractile experiments is reported. Only type IIx muscle fibres were identified in the caracal sample, whereas type IIx and only two type I fibres were found in the lion sample. Only pure type I and IIa, and hybrid type IIax fibres were identified in the human samples - there were no pure type IIx fibres. Nevertheless, compared with all the human fibre types, the lion and caracal fibres were smaller (P<0.01) in cross-sectional area (human: 6194±230 μm(2), lion: 3008±151 μm(2), caracal: 2583±221 μm(2)). On average, the felid type IIx fibres produced significantly greater force (191-211 kN m(-2)) and ~3 times more power (29.0-30.3 kN m(-2) fibre lengths s(-1)) than the human IIax fibres (100-150 kN m(-2), 4-11 kN m(-2) fibre lengths s(-1)). Vmax values of the lion type IIx fibres were also higher than those of human type IIax fibres. The findings suggest that the same fibre type may differ substantially between species and potential explanations are discussed.

  17. Back Analysis of the 2014 San Leo Landslide Using Combined Terrestrial Laser Scanning and 3D Distinct Element Modelling

    NASA Astrophysics Data System (ADS)

    Spreafico, Margherita Cecilia; Francioni, Mirko; Cervi, Federico; Stead, Doug; Bitelli, Gabriele; Ghirotti, Monica; Girelli, Valentina Alena; Lucente, Claudio Corrado; Tini, Maria Alessandra; Borgatti, Lisa

    2016-06-01

    Landslides of the lateral spreading type, involving brittle geological units overlying ductile terrains, are a common occurrence in the sandstone and limestone plateaux of the northern Apennines of Italy. The edges of these plateaux are often the location of rapid landslide phenomena, such as rock slides, rock falls and topples. In this paper, we present a back analysis of a recent landslide (February 2014), involving the north-eastern sector of the San Leo rock slab (northern Apennines, Emilia-Romagna Region) which is a representative example of this type of phenomena. The aquifer hosted in the fractured slab, due to its relatively higher secondary permeability in comparison to the lower clayey units leads to the development of perennial and ephemeral springs at the contact between the two units. The related piping erosion phenomena, together with slope processes in the clay-shales have led to the progressive undermining of the slab, eventually predisposing large-scale landslides. Stability analyses were conducted coupling terrestrial laser scanning (TLS) and distinct element methods (DEMs). TLS point clouds were analysed to determine the pre- and post-failure geometry, the extension of the detachment area and the joint network characteristics. The block dimensions in the landslide deposit were mapped and used to infer the spacing of the discontinuities for insertion into the numerical model. Three-dimensional distinct element simulations were conducted, with and without undermining of the rock slab. The analyses allowed an assessment of the role of the undermining, together with the presence of an almost vertical joint set, striking sub-parallel to the cliff orientation, on the development of the slope instability processes. Based on the TLS and on the numerical simulation results, an interpretation of the landslide mechanism is proposed.

  18. Sustainable Systems for exploration, stays with increased duration in LEO and Earth application -an overview about life support activities

    NASA Astrophysics Data System (ADS)

    Slenzka, Klaus; Duenne, Matthias

    Solar system exploration with extended stays in totally closed habitats far away from Earth as well as longer stays in LEO requires intensive preparatory activities. Activities supporting life in a more or less close meaning are essential in this context -on a scientific as well as on a technical level. These needed activities are supporting life by e.g.: i) increasing knowledge about the impact of single and combined effects of different exploration related environmental conditions (e. g. microgravity, radiation, reduced pressure and temperature, lunar soil etc.) on biological systems. This is needed to enable safe life of humans itself as well as safe operating of required bioregenerative life support systems. Thus, different human cell types as well as representatives of bioregenerative life support system protagonists (algae, bacteria as well as higher organisms) needs to be addressed. ii) provision of required consumables (oxygen, food, energy equivalents etc.) on site, mainly via bioregenerative life support systems, Bio-ISRU-units etc. Preparation is needed on a scientific as well as technological level. iii) ensuring reduced negative effects on humans (and partially also equipment), which could be caused by living in a closed habitat in general (and thus being not space related per se): E. g. detection systems for the quality of water and air, antimicrobial and selfhealing as well as anti-icing materials without dangerous hazard substances, psychological health enhancing components etc. Referring payloads for above mentioned investigations (scientific evaluation and technology demonstration) must be developed. Extended stays and extended closure in habitats without the possibility of material transport into and out of the system are leading to the necessity of more autonomous technologies and sustainable processes. Latter one will rely mainly on biological processes and structures, which increases additionally the necessity of an intensive scientific and

  19. Pride diaries: sex, brain size and sociality in the African lion (Panthera leo) and cougar (Puma concolor).

    PubMed

    Arsznov, Bradley M; Sakai, Sharleen T

    2012-01-01

    The purpose of this study was to examine if differences in social life histories correspond to intraspecific variation in total or regional brain volumes in the African lion (Panthera leo) and cougar (Puma concolor). African lions live in gregarious prides usually consisting of related adult females, their dependent offspring, and a coalition of immigrant males. Upon reaching maturity, male lions enter a nomadic and often, solitary phase in their lives, whereas females are mainly philopatric and highly social throughout their lives. In contrast, the social life history does not differ between male and female cougars; both are solitary. Three-dimensional virtual endocasts were created using computed tomography from the skulls of 14 adult African lions (8 male, 6 female) and 14 cougars (7 male, 7 female). Endocranial volume and basal skull length were highly correlated in African lions (r = 0.59, p < 0.05) and in cougars (r = 0.67, p < 0.01). Analyses of total endocranial volume relative to skull length revealed no sex differences in either African lions or cougars. However, relative anterior cerebrum volume comprised primarily of frontal cortex and surface area was significantly greater in female African lions than males, while relative posterior cerebrum volume and surface area was greater in males than females. These differences were specific to the neocortex and were not found in the solitary cougar, suggesting that social life history is linked to sex-specific neocortical patterns in these species. We further hypothesize that increased frontal cortical volume in female lions is related to the need for greater inhibitory control in the presence of a dominant male aggressor.

  20. Requirements for an Advanced Low Earth Orbit (LEO) Sounder (ALS) for Improved Regional Weather Prediction and Monitoring of Greenhouse Gases

    NASA Technical Reports Server (NTRS)

    Pagano, Thomas S.; Chahine, Moustafa T.; Susskind, Joel

    2008-01-01

    Hyperspectral infrared atmospheric sounders (e.g., the Atmospheric Infrared Sounder (AIRS) on Aqua and the Infrared Atmospheric Sounding Interferometer (IASI) on Met Op) provide highly accurate temperature and water vapor profiles in the lower to upper troposphere. These systems are vital operational components of our National Weather Prediction system and the AIRS has demonstrated over 6 hrs of forecast improvement on the 5 day operational forecast. Despite the success in the mid troposphere to lower stratosphere, a reduction in sensitivity and accuracy has been seen in these systems in the boundary layer over land. In this paper we demonstrate the potential improvement associated with higher spatial resolution (1 km vs currently 13.5 km) on the accuracy of boundary layer products with an added consequence of higher yield of cloud free scenes. This latter feature is related to the number of samples that can be assimilated and has also shown to have a significant impact on improving forecast accuracy. We also present a set of frequencies and resolutions that will improve vertical resolution of temperature and water vapor and trace gas species throughout the atmosphere. Development of an Advanced Low Earth Orbit (LEO) Sounder (ALS) with these improvements will improve weather forecast at the regional scale and of tropical storms and hurricanes. Improvements are also expected in the accuracy of the water vapor and cloud properties products, enhancing process studies and providing a better match to the resolution of future climate models. The improvements of technology required for the ALS are consistent with the current state of technology as demonstrated in NASA Instrument Incubator Program and NOAA's Hyperspectral Environmental Suite (HES) formulation phase development programs.

  1. Evaluation of Error Correcting Code performances of a free space optical communication system between LEO satellite and Ground Station

    NASA Astrophysics Data System (ADS)

    Chochol, M.; Rissons, A.; Lacan, J.; Vedrenne, N.; Artaud, G.

    2015-10-01

    The use of optical communication to transfer data between LEO satellite and optical ground station is being studied. It creates the opportunities to highly increase a transmitted data rate across a free space. The optical propagation channel has specificities that imply the potential use of error correcting code (ECC) and interleaving at physical and higher layer. The study aims to assess the performance of a combination of ECC and interleaving in presence of various channel scenarios and receiver architectures. As a result of these studies, a functional physical layer simulator is provided. The simulator emulates a signal generation and applies time series representing the propagation channel with an effect of receiver front-ends. It also features various detection methods and computes mutual information (MI) in order to approximate ECC performances. A number of receiver architectures and channel scenarios were studied. The channel scenarios combine a direct coupling of the received signal into the photo-detector (PD) and among other assume the use of pre-amplified receiver implying the signal coupling into a standard single mode fiber (SSMF) prior to the detection. Time series were generated and represent the power received at PD input depending on the chosen scenarios (without adaptive optics (AO), with tip-tilt correction, with no dynamical coupling losses or with higher order AO correction). Two modulations of OOK and DBPSK along with various detection methods were examined. The tuning of ECC parameters was studied through the computation of mutual information. Additionally two cases of physical and higher layer interleaving were implemented providing an excellent diversity to the channel seen by the codeword of ECC.

  2. Tropospheric IWV profiles estimation through multifrequency signal attenuation measurements between two counter-rotating LEO satellites: performance analysis

    NASA Astrophysics Data System (ADS)

    Facheris, Luca; Cuccoli, Fabrizio; Martini, Enrica

    2013-10-01

    The exploitation of multifrequency differential attenuation measurements at microwaves made between two LEO satellites in limb mode is the ground of the NDSA (Normalized Differential Spectral Attenuation) approach for estimating integrated tropospheric water vapor profiles through multifrequency measurements at 17, 19, 21, 179 and 182 GHz, plus 32 GHz for liquid water detection and correction (whenever possible). Such measurements are affected by two kinds of impairments, the first generated by thermal noise at the receiver, the second generated by the signals' fluctuations due to the variations of the tropospheric refraction index and referred to as scintillation disturbance. Characterizing scintillation for simulating its effects to evaluate NDSA performance is not easy in general: in particular, it is quite hard (and also rather questionable so some extent) to relate the scintillation parameters to a given simulated atmospheric situation. For this reason, in the past years we limited ourselves to evaluate the NDSA performance by accounting for scintillation in a parametric way, independently of the atmospheric context in which simulations were carried out. In this paper, instead, we show the first results of the NDSA performance analysis based on a completely different approach, where the scintillation profiles and parameters are directly derived from the simulated atmospheric context, based on a procedure that starts from high resolution radiosonde data. A brief critical analysis of such an approach is proposed, evidencing some aspects related to the current knowledge of the scintillation spectra and parameters. The NDSA performance analysis based on certain hypotheses for the scintillation characteristics is then shown for some selected simulated atmospheric conditions.

  3. Intracranial self-stimulation reward thresholds during morphine withdrawal in rats bred for high (HiS) and low (LoS) saccharin intake

    PubMed Central

    Holtz, Nathan A.; Radke, Anna K.; Zlebnik, Natalie E.; Harris, Andrew C.; Carroll, Marilyn E.

    2015-01-01

    Rational Sweet preference is a marker of vulnerability to substance use disorders, and rats selectively bred for high (HiS) vs. low saccharin (LoS) intake display potentiated drug-seeking behaviors. Recent work indicated that LoS rats were more responsive to the negative effects of drugs in several assays. Objective The current study used the intracranial self-stimulation (ICSS) procedure to investigate the anhedonic component of morphine withdrawal in male HiS and LoS rats. Methods Rats were administered morphine (10 mg/kg) or saline for 8 days. To evaluate withdrawal effects, reward thresholds were measured 24 and 28 h following the 8th morphine injection (spontaneous withdrawal) and again for 4 days following daily acute morphine and naloxone (1 mg/kg) administration (precipitated withdrawal). Results Twenty-four hr following the final morphine injection, reward thresholds in LoS rats were significantly elevated compared to reward thresholds in LoS controls, indicating spontaneous withdrawal. This effect was not observed in HiS rats. LoS rats also showed greater elevations of reward thresholds on several days during naloxone-precipitated withdrawal compared to their HiS counterparts. Conclusions LoS rats were more sensitive to morphine withdrawal-mediated elevations in ICSS thresholds than HiS rats. While these differences were generally modest, our data suggest that severity of the negative affective component of opiate withdrawal may be influenced by genotypes related to addiction vulnerability. PMID:25582876

  4. Characteristics of Offshore Hawai';i Island Seismicity and Velocity Structure, including Lo';ihi Submarine Volcano

    NASA Astrophysics Data System (ADS)

    Merz, D. K.; Caplan-Auerbach, J.; Thurber, C. H.

    2013-12-01

    The Island of Hawai';i is home to the most active volcanoes in the Hawaiian Islands. The island's isolated nature, combined with the lack of permanent offshore seismometers, creates difficulties in recording small magnitude earthquakes with accuracy. This background offshore seismicity is crucial in understanding the structure of the lithosphere around the island chain, the stresses on the lithosphere generated by the weight of the islands, and how the volcanoes interact with each other offshore. This study uses the data collected from a 9-month deployment of a temporary ocean bottom seismometer (OBS) network fully surrounding Lo';ihi volcano. This allowed us to widen the aperture of earthquake detection around the Big Island, lower the magnitude detection threshold, and better constrain the hypocentral depths of offshore seismicity that occurs between the OBS network and the Hawaii Volcano Observatory's land based network. Although this study occurred during a time of volcanic quiescence for Lo';ihi, it establishes a basis for background seismicity of the volcano. More than 480 earthquakes were located using the OBS network, incorporating data from the HVO network where possible. Here we present relocated hypocenters using the double-difference earthquake location algorithm HypoDD (Waldhauser & Ellsworth, 2000), as well as tomographic images for a 30 km square area around the summit of Lo';ihi. Illuminated by using the double-difference earthquake location algorithm HypoDD (Waldhauser & Ellsworth, 2000), offshore seismicity during this study is punctuated by events locating in the mantle fault zone 30-50km deep. These events reflect rupture on preexisting faults in the lower lithosphere caused by stresses induced by volcano loading and flexure of the Pacific Plate (Wolfe et al., 2004; Pritchard et al., 2007). Tomography was performed using the double-difference seismic tomography method TomoDD (Zhang & Thurber, 2003) and showed overall velocities to be slower than

  5. Reduced emotional signs of opiate withdrawal in rats selectively bred for low (LoS) versus high (HiS) saccharin intake

    PubMed Central

    Radke, Anna K.; Holtz, Nathan A.; Gewirtz, Jonathan C.; Carroll, Marilyn E.

    2013-01-01

    Rationale Rats bred for high (HiS) and low (LoS) saccharin intake exhibit divergent behavioral responses to multiple drugs of abuse, with HiS rats displaying greater vulnerability to drug taking. Previous research indicates that this effect may be due to increased sensitivity to reward in HiS rats and to the aversive effects of acute drug administration in LoS rats. Objective The current study investigated whether HiS and LoS rats also exhibit different behavioral signs of withdrawal following one or repeated opiate exposures. Methods Emotional signs of opiate withdrawal were assessed with potentiation of the acoustic startle reflex and conditioned place aversion (CPA) in male and female HiS and LoS rats. Startle was measured before and 4 h after a 10 mg/kg injection of morphine on days 1, 2, and 7 of opiate exposure. CPA was induced with a two-day, naloxone-precipitated conditioning paradigm. Somatic signs of withdrawal and weight loss were used also measured. Results Male and female LoS rats exhibited lower startle potentiation than HiS rats on the seventh day of morphine exposure. LoS male rats also failed to develop a CPA to morphine withdrawal. No differences in physical withdrawal signs were observed between HiS and LoS rats, but males of both lines had more physical signs of withdrawal than females. Conclusions These results suggest that LoS rats are less vulnerable to the negative emotional effects of morphine withdrawal than HiS rats. A less severe withdrawal syndrome may contribute to decreased levels of drug taking in the LoS line. PMID:23254375

  6. 6-Gingerol Inhibits Growth of Colon Cancer Cell LoVo via Induction of G2/M Arrest.

    PubMed

    Lin, Ching-Bin; Lin, Chun-Che; Tsay, Gregory J

    2012-01-01

    6-Gingerol, a natural component of ginger, has been widely reported to possess antiinflammatory and antitumorigenic activities. Despite its potential efficacy against cancer, the anti-tumor mechanisms of 6-gingerol are complicated and remain sketchy. In the present study, we aimed to investigate the anti-tumor effects of 6-gingerol on colon cancer cells. Our results revealed that 6-gingerol treatment significantly reduced the cell viability of human colon cancer cell, LoVo, in a dose-dependent manner. Further flow cytometric analysis showed that 6-gingerol induced significant G2/M phase arrest and had slight influence on sub-G1 phase in LoVo cells. Therefore, levels of cyclins, cyclin-dependent kinases (CDKs), and their regulatory proteins involved in S-G2/M transition were investigated. Our findings revealed that levels of cyclin A, cyclin B1, and CDK1 were diminished; in contrast, levels of the negative cell cycle regulators p27(Kip1) and p21(Cip1) were increased in response to 6-gingerol treatment. In addition, 6-gingerol treatment elevated intracellular reactive oxygen species (ROS) and phosphorylation level of p53. These findings indicate that exposure of 6-gingerol may induce intracellular ROS and upregulate p53, p27(Kip1), and p21(Cip1) levels leading to consequent decrease of CDK1, cyclin A, and cyclin B1 as result of cell cycle arrest in LoVo cells. It would be suggested that 6-gingerol should be beneficial to treatment of colon cancer.

  7. The origins of metamodality in visual object area LO: Bodily topographical biases and increased functional connectivity to S1

    PubMed Central

    Tal, Zohar; Geva, Ran; Amedi, Amir

    2016-01-01

    Recent evidence from blind participants suggests that visual areas are task-oriented and sensory modality input independent rather than sensory-specific to vision. Specifically, visual areas are thought to retain their functional selectivity when using non-visual inputs (touch or sound) even without having any visual experience. However, this theory is still controversial since it is not clear whether this also characterizes the sighted brain, and whether the reported results in the sighted reflect basic fundamental a-modal processes or are an epiphenomenon to a large extent. In the current study, we addressed these questions using a series of fMRI experiments aimed to explore visual cortex responses to passive touch on various body parts and the coupling between the parietal and visual cortices as manifested by functional connectivity. We show that passive touch robustly activated the object selective parts of the lateral–occipital (LO) cortex while deactivating almost all other occipital–retinotopic-areas. Furthermore, passive touch responses in the visual cortex were specific to hand and upper trunk stimulations. Psychophysiological interaction (PPI) analysis suggests that LO is functionally connected to the hand area in the primary somatosensory homunculus (S1), during hand and shoulder stimulations but not to any of the other body parts. We suggest that LO is a fundamental hub that serves as a node between visual-object selective areas and S1 hand representation, probably due to the critical evolutionary role of touch in object recognition and manipulation. These results might also point to a more general principle suggesting that recruitment or deactivation of the visual cortex by other sensory input depends on the ecological relevance of the information conveyed by this input to the task/computations carried out by each area or network. This is likely to rely on the unique and differential pattern of connectivity for each visual area with the rest of the

  8. Interstellar Hydrogen Fluxes Measured by IBEX-Lo in 2009: Numerical Modeling and Comparison with the Data

    NASA Astrophysics Data System (ADS)

    Katushkina, O. A.; Izmodenov, V. V.; Alexashov, D. B.; Schwadron, N. A.; McComas, D. J.

    2015-10-01

    In this paper, we perform numerical modeling of the interstellar hydrogen fluxes measured by IBEX-Lo during orbit 23 (spring 2009) using a state-of-the-art kinetic model of the interstellar neutral hydrogen distribution in the heliosphere. This model takes into account the temporal and heliolatitudinal variations of the solar parameters as well as the non-Maxwellian kinetic properties of the hydrogen distribution due to charge exchange in the heliospheric interface. We found that there is a qualitative difference between the IBEX-Lo data and the modeling results obtained with the three-dimensional, time-dependent model. Namely, the model predicts a larger count rate in energy bin 2 (20-41 eV) than in energy bin 1 (11-21 eV), while the data shows the opposite case. We perform study of the model parameter effects on the IBEX-Lo fluxes and the ratio of fluxes in two energy channels. We show that the most important parameter, which has a major influence on the ratio of the fluxes in the two energy bins, is the solar radiation pressure. The parameter fitting procedure shows that the best agreement between the model result and the data occurs when the ratio of the solar radiation pressure to the solar gravitation, μ0, is {1.26}-0.076+0.06, and the total ionization rate of hydrogen at 1 AU is {β }E,0={3.7}-0.35+0.39× {10}-7 s-1. We have found that the value of μ0 is much larger than μ0 = 0.89, which is the value derived from the integrated solar Lyα flux data for the period of time studied. We discuss possible reasons for the differences.

  9. The origins of metamodality in visual object area LO: Bodily topographical biases and increased functional connectivity to S1.

    PubMed

    Tal, Zohar; Geva, Ran; Amedi, Amir

    2016-02-15

    Recent evidence from blind participants suggests that visual areas are task-oriented and sensory modality input independent rather than sensory-specific to vision. Specifically, visual areas are thought to retain their functional selectivity when using non-visual inputs (touch or sound) even without having any visual experience. However, this theory is still controversial since it is not clear whether this also characterizes the sighted brain, and whether the reported results in the sighted reflect basic fundamental a-modal processes or are an epiphenomenon to a large extent. In the current study, we addressed these questions using a series of fMRI experiments aimed to explore visual cortex responses to passive touch on various body parts and the coupling between the parietal and visual cortices as manifested by functional connectivity. We show that passive touch robustly activated the object selective parts of the lateral-occipital (LO) cortex while deactivating almost all other occipital-retinotopic-areas. Furthermore, passive touch responses in the visual cortex were specific to hand and upper trunk stimulations. Psychophysiological interaction (PPI) analysis suggests that LO is functionally connected to the hand area in the primary somatosensory homunculus (S1), during hand and shoulder stimulations but not to any of the other body parts. We suggest that LO is a fundamental hub that serves as a node between visual-object selective areas and S1 hand representation, probably due to the critical evolutionary role of touch in object recognition and manipulation. These results might also point to a more general principle suggesting that recruitment or deactivation of the visual cortex by other sensory input depends on the ecological relevance of the information conveyed by this input to the task/computations carried out by each area or network. This is likely to rely on the unique and differential pattern of connectivity for each visual area with the rest of the

  10. Hydrogeology and analysis of ground-water withdrawal in the Mendenhall-D'Lo area, Simpson County, Mississippi

    USGS Publications Warehouse

    Strom, E.W.; Oakley, W.T.

    1995-01-01

    The cities of Mendenhall and D'Lo, located in Simpson County, rely on ground water for their public supply and industrial needs. Most of the ground water comes from an aquifer of Miocene age. A study began in 1991 to describe the hydrogeology, analyze effects of ground-water withdrawal by making a drawdown map, and estimate the effects increased ground-water withdrawal might have on water levels in the Miocene age aquifer in the Mendenhall-D'Lo area. The most significant withdrawals of ground water in the study area are from 10 wells screened in the lower sand of the Catahoula Formation of Miocene age. Analysis of the effect of withdrawals from the 10 wells was made using the Theis non- equilibrium equation and applying the principle of superposition. Analysis of 1994 conditions was based on the pumpage history and aquifer properties deter- mined for each well. The drawdown surface resulting from the analysis indicates three general cones of depression. One cone is in the northwestern D'Lo area, one in the south-central Mendenhall area, and one about 1-1/2 miles east of Mendenhall. Calculated drawdown ranges from 21 to 47 feet. Potential drawdown-surface maps were made for 10 years and 20 years beyond 1994 using a constant pumpage. The map made for 10 years beyond 1994 indicates an average total increase in drawdown of about 5.3 feet. The map made for 20 years beyond 1994 indicates an average total increase in drawdown of about 7.3 feet.

  11. Seasonality and paleoecology of the late Cretaceous multi-taxa vertebrate assemblage of "Lo Hueco" (central eastern Spain).

    PubMed

    Domingo, Laura; Barroso-Barcenilla, Fernando; Cambra-Moo, Oscar

    2015-01-01

    Isotopic studies of multi-taxa terrestrial vertebrate assemblages allow determination of paleoclimatic and paleoecological aspects on account of the different information supplied by each taxon. The late Campanian-early Maastrichtian "Lo Hueco" Fossil-Lagerstätte (central eastern Spain), located at a subtropical paleolatitude of ~31°N, constitutes an ideal setting to carry out this task due to its abundant and diverse vertebrate assemblage. Local δ18OPO4 values estimated from δ18OPO4 values of theropods, sauropods, crocodyliforms, and turtles are close to δ18OH2O values observed at modern subtropical latitudes. Theropod δ18OH2O values are lower than those shown by crocodyliforms and turtles, indicating that terrestrial endothermic taxa record δ18OH2O values throughout the year, whereas semiaquatic ectothermic taxa δ18OH2O values represent local meteoric waters over a shorter time period when conditions are favorable for bioapatite synthesis (warm season). Temperatures calculated by combining theropod, crocodyliform, and turtle δ18OH2O values and gar δ18OPO4 have enabled us to estimate seasonal variability as the difference between mean annual temperature (MAT, yielded by theropods) and temperature of the warmest months (TWMs, provided by crocodyliforms and turtles). ΔTWMs-MAT value does not point to a significantly different seasonal thermal variability when compared to modern coastal subtropical meteorological stations and Late Cretaceous rudists from eastern Tethys. Bioapatite and bulk organic matter δ13C values point to a C3 environment in the "Lo Hueco" area. The estimated fractionation between sauropod enamel and diet is ~15‰. While waiting for paleoecological information yielded by the ongoing morphological study of the "Lo Hueco" crocodyliforms, δ13C and δ18OCO3 results point to incorporation of food items with brackish influence, but preferential ingestion of freshwater. "Lo Hueco" turtles showed the lowest δ13C and δ18OCO3 values of the

  12. Seasonality and Paleoecology of the Late Cretaceous Multi-Taxa Vertebrate Assemblage of “Lo Hueco” (Central Eastern Spain)

    PubMed Central

    Domingo, Laura; Barroso-Barcenilla, Fernando; Cambra-Moo, Oscar

    2015-01-01

    Isotopic studies of multi-taxa terrestrial vertebrate assemblages allow determination of paleoclimatic and paleoecological aspects on account of the different information supplied by each taxon. The late Campanian-early Maastrichtian “Lo Hueco” Fossil-Lagerstätte (central eastern Spain), located at a subtropical paleolatitude of ~31°N, constitutes an ideal setting to carry out this task due to its abundant and diverse vertebrate assemblage. Local δ18OPO4 values estimated from δ18OPO4 values of theropods, sauropods, crocodyliforms, and turtles are close to δ18OH2O values observed at modern subtropical latitudes. Theropod δ18OH2O values are lower than those shown by crocodyliforms and turtles, indicating that terrestrial endothermic taxa record δ18OH2O values throughout the year, whereas semiaquatic ectothermic taxa δ18OH2O values represent local meteoric waters over a shorter time period when conditions are favorable for bioapatite synthesis (warm season). Temperatures calculated by combining theropod, crocodyliform, and turtle δ18OH2O values and gar δ18OPO4 have enabled us to estimate seasonal variability as the difference between mean annual temperature (MAT, yielded by theropods) and temperature of the warmest months (TWMs, provided by crocodyliforms and turtles). ΔTWMs-MAT value does not point to a significantly different seasonal thermal variability when compared to modern coastal subtropical meteorological stations and Late Cretaceous rudists from eastern Tethys. Bioapatite and bulk organic matter δ13C values point to a C3 environment in the “Lo Hueco” area. The estimated fractionation between sauropod enamel and diet is ~15‰. While waiting for paleoecological information yielded by the ongoing morphological study of the “Lo Hueco” crocodyliforms, δ13C and δ18OCO3 results point to incorporation of food items with brackish influence, but preferential ingestion of freshwater. “Lo Hueco” turtles showed the lowest δ13C and δ18OCO3

  13. Advantages of Karhunen Loève transform over fast Fourier transform for planetary radar and space debris detection

    NASA Astrophysics Data System (ADS)

    Maccone, Claudio

    2007-04-01

    The present article describes that the range of any radiotelescope (and radar in general) may be increased by virtue of software, if one replaces the fast Fourier transform by the Karhunen Loève transform. The range increases with the inverse of the fourth root of the signal-to-noise ratio when this ratio decreases. Thus, the range on any radiotelescope (and radar) may be increased without changing the hardware at all, but by changing the software only. This improvement in the range of the radiotelescope is currently implemented at the 32-m antenna located at Medicina, near Bologna, in Italy, for both SETI and general radioastronomy.

  14. Seasonality and paleoecology of the late Cretaceous multi-taxa vertebrate assemblage of "Lo Hueco" (central eastern Spain).

    PubMed

    Domingo, Laura; Barroso-Barcenilla, Fernando; Cambra-Moo, Oscar

    2015-01-01

    Isotopic studies of multi-taxa terrestrial vertebrate assemblages allow determination of paleoclimatic and paleoecological aspects on account of the different information supplied by each taxon. The late Campanian-early Maastrichtian "Lo Hueco" Fossil-Lagerstätte (central eastern Spain), located at a subtropical paleolatitude of ~31°N, constitutes an ideal setting to carry out this task due to its abundant and diverse vertebrate assemblage. Local δ18OPO4 values estimated from δ18OPO4 values of theropods, sauropods, crocodyliforms, and turtles are close to δ18OH2O values observed at modern subtropical latitudes. Theropod δ18OH2O values are lower than those shown by crocodyliforms and turtles, indicating that terrestrial endothermic taxa record δ18OH2O values throughout the year, whereas semiaquatic ectothermic taxa δ18OH2O values represent local meteoric waters over a shorter time period when conditions are favorable for bioapatite synthesis (warm season). Temperatures calculated by combining theropod, crocodyliform, and turtle δ18OH2O values and gar δ18OPO4 have enabled us to estimate seasonal variability as the difference between mean annual temperature (MAT, yielded by theropods) and temperature of the warmest months (TWMs, provided by crocodyliforms and turtles). ΔTWMs-MAT value does not point to a significantly different seasonal thermal variability when compared to modern coastal subtropical meteorological stations and Late Cretaceous rudists from eastern Tethys. Bioapatite and bulk organic matter δ13C values point to a C3 environment in the "Lo Hueco" area. The estimated fractionation between sauropod enamel and diet is ~15‰. While waiting for paleoecological information yielded by the ongoing morphological study of the "Lo Hueco" crocodyliforms, δ13C and δ18OCO3 results point to incorporation of food items with brackish influence, but preferential ingestion of freshwater. "Lo Hueco" turtles showed the lowest δ13C and δ18OCO3 values of the

  15. Optical and X-ray studies of chromospherically active stars: FR Cancri, HD 95559 and LO Pegasi

    NASA Technical Reports Server (NTRS)

    Pandey, J. C.; Singh, K. P.; Drake, S. A.; Sagar, R.

    2005-01-01

    We present a multiwavelength study of three chromospherically active stars, namely FR Cnc (= BD +16 degrees 1753), HD 95559 and LO Peg (=BD +22 degrees 4409), including newly obtained optical photometry, (for FR Cnc) low-resolution optical spectroscopy, as well as archival IR and X-ray observations. The BVR photometry carried out during the years 2001 - 2004 has found significant photometric variability to be present in all three stars. For FR Cnc, a photometric period 0.826685 +/- 0.000034 d has been established. The strong variation in the phase and amplitude of the FR Cnc light curves when folded on this period implies the presence of evolving and migrating spots or spot groups on its surface. Two independent spots with migration periods of 0.97 and 0.93 years respectively are inferred. The photometry of HD 95559 suggests the formation of a spot (group) during the interval of our observations. We infer the existence of two independent spots or groups in the photosphere of LO Peg, one of which has a migration period of 1.12 years. The optical spectroscopy of FR Cnc carried out during 2002-2003, reveals the presence of strong and variable Ca I1 H and K, H(sub beta) and H(sub alpha) emission features indicative of high level of chromospheric activity. The value of 5.3 for the ratio of the excess emission in H(sub alpha) to H(sub beta), EH(sub alpha)/EH(sub beta), suggests that the chromospheric emission may arise from an extended off-limb region. We have searched for the presence of color excesses in the near-IR JHK bands of these stars using 2MASS data, but none of them appear to have any significant color excess. We have also analyzed archival X-ray observations of HD 95559 and LO Peg carried out by with the ROSAT observatory. The best fit models to their X-ray spectra imply the presence of two coronal plasma components of differing temperatures and with sub-solar metal abundances. The inferred emission measures and temperatures of these systems are similar to

  16. Production of lion (Panthera leo) blastocysts after in vitro maturation of oocytes and intracytoplasmic sperm injection.

    PubMed

    Fernandez-Gonzalez, Lorena; Hribal, Romy; Stagegaard, Julia; Zahmel, Jennifer; Jewgenow, Katarina

    2015-04-01

    Assisted reproductive techniques are becoming widely applied to the breeding of endangered species, but establishing reliable protocols for the production of embryos in vitro is challenging because of the scarcity of sample material. In our study, we applied an assisted reproductive technique protocol for IVM and intracytoplasmic sperm injection (ICSI), developed in the domestic cat, to oocytes retrieved from ovaries of four 2-year-old lionesses (Panthera leo) eight hours postmortem. In total, 68 cumulus-oocyte complexes of good quality were randomly distributed and cultured for 32 to 34 hours in two different maturation culture media, consisting of Medium 199 with Earle's salts, 3 mg/mL BSA, 0.1 mg/mL cysteine, 1.4 mg/mL sodium pyruvate, 0.6 mg/mL sodium lactate, 0.15 mg/mL l-glutamine, and 0.055 mg/mL gentamicin. Hormonal supplementation of IVM_1 was 0.02 IU/mL FSH and 0.05 IU/mL LH; IVM_2 consisted of 1.64 IU/mL FSH, 1.06 IU/mL LH, and 1 μg/mL 17ß-estradiol. Differences in hormonal supplementation did not produce significant differences in oocyte maturation rates, which were 39.4% in IVM_1 and 34.3% in IVM_2. Matured oocytes were microinjected with homologous frozen-thawed spermatozoa, and subsequent cleavage rates were 30.8% and 58.3%, respectively. Half of the embryos derived from oocytes matured in IVM_1 developed into blastocysts, whereas only 28.6% of embryos from oocytes matured in IVM_2 reached the blastocyst stage. Morula stages were present from Day 6 onward, and blastocyst stages from Day 9 on, indicating a slower developmental speed in comparison with domestic cats. This is the first report of in vitro-produced blastocysts using ICSI in the lion, and the results report that IVM and ICSI can be successfully performed with cumulus-oocyte complexes retrieved from ovaries after eight hours of shipping, obtaining competent embryos in culture.

  17. Operational specification and forecasting advances for Dst, LEO thermospheric densities, and aviation radiation dose and dose rate

    NASA Astrophysics Data System (ADS)

    Tobiska, W.; Knipp, D. J.; Burke, W. J.; Bouwer, D.; Bailey, J. J.; Hagan, M. P.; Didkovsky, L. V.; Garrett, H. B.; Bowman, B. R.; Gannon, J. L.; Atwell, W.; Blake, J. B.; Crain, W.; Rice, D.; Schunk, R. W.; Fulgham, J.; Bell, D.; Gersey, B.; Wilkins, R.; Fuschino, R.; Flynn, C.; Cecil, K.; Mertens, C. J.; Xu, X.; Crowley, G.; Reynolds, A.; Azeem, S. I.; Wiley, S.; Holland, M.; Malone, K.

    2013-12-01

    Space weather's effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun's photons, particles, and fields. Of the space environment domains that are affected by space weather, the magnetosphere, thermosphere, and even troposphere are key regions that are affected. Space Environment Technologies (SET) has developed and is producing innovative space weather applications. Key operational systems for providing timely information about the effects of space weather on these domains are SET's Magnetosphere Alert and Prediction System (MAPS), LEO Alert and Prediction System (LAPS), and Automated Radiation Measurements for Aviation Safety (ARMAS) system. MAPS provides a forecast Dst index out to 6 days through the data-driven, redundant data stream Anemomilos algorithm. Anemomilos uses observational proxies for the magnitude, location, and velocity of solar ejecta events. This forecast index is used by satellite operations to characterize upcoming geomagnetic storms, for example. LAPS is the SET fully redundant operational system providing recent history, current epoch, and forecast solar and geomagnetic indices for use in operational versions of the JB2008 thermospheric density model. The thermospheric densities produced by that system, driven by the LAPS data, are forecast to 72-hours to provide the global mass densities for satellite operators. ARMAS is a project that has successfully demonstrated the operation of a micro dosimeter on aircraft to capture the real-time radiation environment due to Galactic Cosmic Rays and Solar Energetic Particles. The dose and dose-rates are captured on aircraft, downlinked in real-time via the Iridium satellites, processed on the ground, incorporated into the most recent NAIRAS global radiation climatology data runs, and made available to end users via the web and smart phone apps. ARMAS provides the 'weather' of the radiation environment to improve air-crew and passenger safety

  18. Operational specification and forecasting advances for Dst, LEO thermospheric densities, and aviation radiation dose and dose rate

    NASA Astrophysics Data System (ADS)

    Tobiska, W. Kent

    Space weather’s effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun’s photons, particles, and fields. Of the space environment domains that are affected by space weather, the magnetosphere, thermosphere, and even troposphere are key regions that are affected. Space Environment Technologies (SET) has developed and is producing innovative space weather applications. Key operational systems for providing timely information about the effects of space weather on these domains are SET’s Magnetosphere Alert and Prediction System (MAPS), LEO Alert and Prediction System (LAPS), and Automated Radiation Measurements for Aviation Safety (ARMAS) system. MAPS provides a forecast Dst index out to 6 days through the data-driven, redundant data stream Anemomilos algorithm. Anemomilos uses observational proxies for the magnitude, location, and velocity of solar ejecta events. This forecast index is used by satellite operations to characterize upcoming geomagnetic storms, for example. In addition, an ENLIL/Rice Dst prediction out to several days has also been developed and will be described. LAPS is the SET fully redundant operational system providing recent history, current epoch, and forecast solar and geomagnetic indices for use in operational versions of the JB2008 thermospheric density model. The thermospheric densities produced by that system, driven by the LAPS data, are forecast to 72-hours to provide the global mass densities for satellite operators. ARMAS is a project that has successfully demonstrated the operation of a micro dosimeter on aircraft to capture the real-time radiation environment due to Galactic Cosmic Rays and Solar Energetic Particles. The dose and dose-rates are captured on aircraft, downlinked in real-time via the Iridium satellites, processed on the ground, incorporated into the most recent NAIRAS global radiation climatology data runs, and made available to end users via the web and

  19. Computer modeling of high-voltage solar array experiment using the NASCAP/LEO (NASA Charging Analyzer Program/Low Earth Orbit) computer code

    NASA Astrophysics Data System (ADS)

    Reichl, Karl O., Jr.

    1987-06-01

    The relationship between the Interactions Measurement Payload for Shuttle (IMPS) flight experiment and the low Earth orbit plasma environment is discussed. Two interactions (parasitic current loss and electrostatic discharge on the array) may be detrimental to mission effectiveness. They result from the spacecraft's electrical potentials floating relative to plasma ground to achieve a charge flow equilibrium into the spacecraft. The floating potentials were driven by external biases applied to a solar array module of the Photovoltaic Array Space Power (PASP) experiment aboard the IMPS test pallet. The modeling was performed using the NASA Charging Analyzer Program/Low Earth Orbit (NASCAP/LEO) computer code which calculates the potentials and current collection of high-voltage objects in low Earth orbit. Models are developed by specifying the spacecraft, environment, and orbital parameters. Eight IMPS models were developed by varying the array's bias voltage and altering its orientation relative to its motion. The code modeled a typical low Earth equatorial orbit. NASCAP/LEO calculated a wide variety of possible floating potential and current collection scenarios. These varied directly with both the array bias voltage and with the vehicle's orbital orientation.

  20. Jet-vetoed Higgs cross section in gluon fusion at N3LO+NNLL with small-R resummation

    NASA Astrophysics Data System (ADS)

    Banfi, Andrea; Caola, Fabrizio; Dreyer, Frédéric A.; Monni, Pier Francesco; Salam, Gavin P.; Zanderighi, Giulia; Dulat, Falko

    2016-04-01

    We present new results for the jet-veto efficiency and zero-jet cross section in Higgs production through gluon fusion. We incorporate the N3LO corrections to the total cross section, the NNLO corrections to the 1-jet rate, NNLL resummation for the jet p t and LL resummation for the jet radius dependence. Our results include known finite-mass corrections and are obtained using the jet-veto efficiency method, updated relative to earlier work to take into account what has been learnt from the new precision calculations that we include. For 13 TeV collisions and using our default choice for the renormalisation and factorisation scales, μ 0 = m H /2, the matched prediction for the jet-veto efficiency increases the pure N3LO prediction by about 2% and the two have comparable uncertainties. Relative to NNLO+NNLL results, the new prediction is 2% smaller and the uncertainty reduces from about 10% to a few percent. Results are also presented for the central scale μ 0 = m H .